coatings

Review
Applicability of Agro-Industrial By-Products in
Intelligent Food Packaging
Silvia Amalia Nemes 1 , Katalin Szabo 1 and Dan Cristian Vodnar 1,2, *
1 Institute of Life Sciences, University of Agricultural Sciences and Veterinary Medicine, Calea Mănăştur 3–5,
400372 Cluj–Napoca, Romania; amalia.nemes@usamvcluj.ro (S.A.N.); katalin.szabo@usamvcluj.ro (K.S.)
2 Faculty of Food Science and Technology, University of Agricultural Sciences and Veterinary Medicine,
Calea Mănăştur 3–5, 400372 Cluj–Napoca, Romania
* Correspondence: dan.vodnar@usamvcluj.ro; Tel.: +40-747341881




Received: 20 May 2020; Accepted: 1 June 2020; Published: 8 June 2020


Abstract: Nowadays, technological advancement is in continuous development in all areas,

including food packaging, which tries to find a balance between consumer preferences, environmental
safety, and issues related to food quality and control. The present paper concretely details the concepts
of smart, active, and intelligent packaging and identifies commercially available examples used in the
food packaging market place. Along with this purpose, several bioactive compounds are identified and
described, which are compounds that can be recovered from the by-products of the food industry and
can be integrated into smart food packaging supporting the “zero waste” activities. The biopolymers
obtained from crustacean processing or compounds with good antioxidant or antimicrobial properties
such as carotenoids extracted from agro-industrial processing are underexploited and inexpensive
resources for this purpose. Along with the main agro-industrial by-products, more concrete examples
of resources are presented, such as grape marc, banana peels, or mango seeds. The commercial and
technological potential of smart packaging in the food industry is undeniable and most importantly,
this paper highlights the possibility of integrating the by-products derived compounds to intelligent
packaging elements (sensors, indicators, radio frequency identification).

Keywords: smart packaging; by-products; antioxidant properties; indicators; sensors; zero-waste;

food quality; shelf-life

1. Introduction
The food packaging concept arose with the desire of humans to conserve food for a longer time,
and it was adapted gradually to the industrialization and commercialization processes [1].
Since the earliest times, people consumed fresh food on the same days when raw materials were
hunted or reaped from the garden without any food preservation issues. With the evolution through
time and the trend of the population to live in communities, the need for food preservation appeared
and food packaging solutions were found. Glass is found as the first material for food packaging in
written history, as a precedent of paper, which is now widely used in the food industry [1]. Moving to
one of the most debated packagings of the contemporary era, plastic material is found in specific
studies from the year 1870 [1]. Back then, brothers John W. Hyatt and Isaiah S. Hyatt had patented the
first commercially available plastic material, which was a mixture containing pyroxylin and camphor
used in the manufacture of objects such as dental plates or shirt collars [1]. The evolution of this
packaging material is spectacular, reaching 380 million metric tons in 2015 globally, covering 40% of
the materials used for packaging. From this ratio, 60% is used only in the food packaging industry,
and the rest is used in areas such as healthcare, cosmetics, or household [2].

Coatings 2020, 10, 550; doi:10.3390/coatings10060550 www.mdpi.com/journal/coatings

Coatings 2020, 10, 550 2 of 26

Regardless of specific domains (e.g., medical, pharmaceutical, automobile, construction),

constant progress can be observed in all fields, as well in the food packaging industry, and a
significant evolution is perceived, according to global digitalization. If in the past few years researchers
were focused on developing new packaging materials, in the present moment, the spotlight relies on
developing new packaging concepts, such as electronic devices (e.g., indicators, sensors) incorporated
in the package, providing more information about the food inside.
Nowadays, the challenge in the food industry is to fulfill consumer demand, which is focused on
healthy, fresh, and the least processed food products. With the need to have relevant options that enhance
their lifestyle, concerning the shorter time for shopping in the supermarket, and less time spent cooking
the food, consumers are also aware of the effects of packaging on the environment. Globalization has
allowed many products from all around the world to be more accessible, and consumers are used to
obtaining these products at any time and relatively at a low cost [3]. As a result of these reasons and
others such as safety, marketing, or cost-effectiveness, producers pay much attention to the packaging
they choose for the products.
At a global level, the food packaging area is one of the most advanced industries, which makes
people think about the economic impact of this manufacturing sector [4]. Advancing this idea, the price
of the packaging is found in the final price of the food, and consumers know this aspect. This is one of
the reasons why it is difficult to introduce a new concept of packaging in the market place, only if its
cost is lower or if the consumer is informed and knows its benefits [5].
In 2009, the food packaging industry was estimated at the value of US$380 billion, and it is one of
the largest packaging industries, representing more than 50% of all packaging industries at a global level.
Plastic is the most imported packaging material, and it is evaluated at $9.5 billion, followed by paper
with $4 billion, glass with $1.6 billion, and wood $0.3 billion. The food packaging market has a huge
economic impact also on the developing countries taken in the study by The Food and Agricultural
Organization of the United Nations (FAO), and its value was estimated at US$15.4 billion [4].
Generally, the package of a product has a substantial role in its journey, beginning with transport,
the distribution process, retailing, and most important, protection and preservation. With all these
efforts, a report published by the World Packaging Organization shows that more than 25% of food
products are wasted because of improper packagings such as inappropriate dosage, an absence of
reclosing function, insufficient storage protection, or smaller package sizes [5]. To solve these specific
problems strongly related to the global concern of food waste, the technologies of food packaging keep
advancing. Furthermore, producers from the packaging market are permanently challenged to develop
new packaging models in line with consumers’ request, which is in a continuous changing process.
Consumer requests are in a continuously changing process; therefore, producers from the
packaging market are permanently challenged to develop new packaging models. The latest trends on
the supermarket’s shelves are the ready-to-eat products with improved shelf life based on the newest
methods, such as active, intelligent, and smart packaging concepts.
Besides the safety improvements for food quality or marketing solutions that smart packaging offers
for consumers and producers, it has an impact also for the economic domain, especially due to the
global market which is expected to be doubled until 2021 [6], and to reach US$26.7 billion until 2024 [7].
For example, active packaging, which is characterized by an active function to extend the shelf life of
the food product through bioactive compounds, was estimated in 2013 to occupy 26.9% from the global
market of the packaging industry, which is evaluated at US$6.4 billion, while intelligent packagings were
estimated at US$2.3 billion [8]. The most relevant countries that develop active and intelligent packaging
are the US, Japan, and Australia. Figure 1 presents the growth rate predicted by 2026 [7].
The main purpose of food packaging is to prolong the shelf life of the food by protecting it from the
outside environment [9]. Improving this aspect and maintaining the quality of the products supposed
to use new strategic methods of fabrication or a new strategy of packaging. Various strategies can
be used for improving the shelf life of a product, such as time–temperature devices, nanomaterials,
the addition of chemicals, carbon dioxide emitters/absorbers, oxygen indicators, and barcode label
Coatings 2020, 10, 550 3 of 26

biosensors [3,10–12]. This kind of packing can be part of two categories, active or intelligent packing,
and if these two methods are combined, it can be called smart packaging [13].
Coatings 2020, 10, x FOR PEER REVIEW 3 of 24

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Coatings 2020, 10, 550 4 of 26

Table 1. Definitions found in the literature for active, intelligent, and smart packaging.

Innovative Packaging Definitions Reference

- “active food contact materials and articles (hereinafter referred to as active materials
and articles) means materials and articles that are intended to extend the shelf life or to
maintain or improve the condition of packaged food. They are designed to deliberately [23]
incorporate components that would release or absorb substances into or from the
Active packaging packaged food or the environment surrounding the food”.
- A system that makes the interaction between the food, packaging, and the environment. [24]

- Packages that increase the shelf life of the food product by using natural compounds
incorporated in the packaging.

- “ ‘intelligent food contact materials and articles’ (hereinafter referred to as intelligent

materials and articles) means materials and articles which monitor the condition of [23]
packaged food or the environment surrounding the food”
- Systems that provide the user with information on the conditions of food and should [25]
not release their constituents into the food.
Intelligent packaging
- A system adept to “sense, detect or record external or internal changes in the product” [19]

- A system added to packaging with the purpose of monitoring (food quality, critical [3]
control points) and giving information about the supply chain.
- “The term “intelligent” involves an “ON/OFF” switching function on the package in
response to changing external/internal stimuli, to communicate the product’s status to [26]
its consumers or end users”

- “Innovative packaging system that combines the benefits of measuring, estimating, or

predicting different aspects of food quality or safety with the release of an active [27]
substance that extends the product shelf life”.
Smart packaging
- The packaging capable of monitoring the changes that can appear in the product, [24]
packaging, or environment.
- Upgraded packaging system with functional attributes that bring benefits to the food [21]
products and consumers.
Coatings 2020, 10, 550 5 of 26

The packaging has a role in preventing contamination of the food product and maintaining its
freshness also. The food validity period can be determined depending on food product specifications
such as the content of saturated and unsaturated fatty acids, enzyme activity, water activity, pH,
or protein content [10,28–30], and the packaging type used as a barrier layer from contamination [19].
The shelf life of a food product is determined as the time between when the product was packaged
and the last day that it can be consumed without any health risks and at the same quality. The expiration
date can be limited by numerous intrinsic and extrinsic factors that are presented in Table 2, which can
influence sensorial, textural, and microbial characteristics [13].

Table 2. Intrinsic and extrinsic factors that can influence the shelf life.

Intrinsic Factors Extrinsic Factors Reference

Water activity Time–temperature profile [9]
pH value Temperature control [31]
Redox potential Relative humidity [13]
Available oxygen Exposure to light [32]
Nutrients Microbial environment [32]
Natural microflora Environment in packaging [9,13]
Biochemical products Heat treatment [13]
Preservative Purchaser handling [13]

Distance between the place of production and place of sale is another issue raised with globalization
that accentuated the drawbacks related to shelf life. Most of the foods are perishable and for this
reason, producers have chosen different methods to improve the product’s shelf life such as cooling,
heat treatment, or modified atmosphere [33]. With all these, the microorganisms are not eliminated,
and they stimulate reducing the quality and food safety. To solve and control this issue, the concept of
active, intelligent, and smart packaging was developed.

3. Smart Packaging
According to many studies, smart packaging is defined as the packaging that includes both
active and intelligent systems acting synergistically, as illustrated in Figure 2. It is capable of
monitoring the changes during storage (increases/decreases in temperature or humidity) and acts to
slow down the quality degradation. Using the compounds from active packagings, such as antioxidants,
emitters of carbon dioxide, antibacterial agents, humidity, ethylene, and oxygen scavengers together
with intelligent devices has obtained the concept named “smart packaging” [7,24,34,35].
Smart packaging includes devices that are capable of heating or cooling food inside and show
in real time the nutritional information on the electronic display [21]. Some of the smart packaging
belonging to the canning and beverage industries has been shown in a study [36]. A device incorporated
in the package that can change the temperature of the food inside was developed for bottles, cans,
or carton packages. It can lower the product’s temperature with 18 ◦ C in a short time (two or three
minutes) before consumption. The principle of this packaging is based on absorbing the heat from the
liquid inside, using the vapors obtained by releasing from a vinyl bag a quantity of pressurized water
that evaporates immediately [37].
Another example of smart packaging is dedicated to heat coffee, tea, soup, and hot chocolate
cups. In this case, the exothermic reaction between water and calcium oxide is the basis. Inside the
cup, calcium and water are placed separately. Consumers are asked to invert the cup and mix the
components, thus activating an exotherm reaction. The material that the cup is made of allows keeping
the temperature for approximately 20 min [36].
active and intelligent systems acting synergistically, as illustrated in Figure 2. It is capable of
monitoring the changes during storage (increases/decreases in temperature or humidity) and acts to
slow down the quality degradation. Using the compounds from active packagings, such as
antioxidants, emitters of carbon dioxide, antibacterial agents, humidity, ethylene, and oxygen
scavengers together with intelligent devices has obtained the concept named “smart packaging”
Coatings 2020, 10, 550 6 of 26
[7,24,34,35].

Figure
Figure 2. Smart packaging
2. Smart packaging concept.
concept.

A new packaging
Smart principle improved
includes is an electronic
devices that aretracking
capabletag, which helps
of heating to have
or cooling better
food control
inside andon the
show
food distribution
in real chain. Appling
time the nutritional the Radio
information onFrequency Identification
the electronic (RFID)
display [21]. Sometechnology waspackaging
of the smart advanced
as a pack that is useful to prevent fraud, decrease economical losses, and enhance
belonging to the canning and beverage industries has been shown in a study [36]. A device the fundamental
operation
incorporatedsuchin as
thestorage,
packagedistribution, and marketing.
that can change RFIDofpackaging
the temperature can bewas
the food inside considered
developedsmart
for
packaging only
bottles, cans, orifcarton
it is used alongside
packages. a sensor
It can lowerorthe
biosensor thattemperature
product’s can providewith
the specific
18 °C in location
a shortoftime
the
product [35].
Oxygen-absorbing technology involves the combination of oxidation of certain compounds
(iron powder, ascorbic acid, photosensitive polymers, enzymes), which are able to reduce the oxygen
level inside the package, from the regular value between 0.3% and 3%, which is found in the conventional
packaging systems such as modified atmosphere, vacuum, or substitution of internal atmosphere to an
oxygen value of 0.01% [30]. Ascorbic acid and sodium bicarbonate were used for the development of a
smart oxygen-absorbing label used in the meat industry. It is working to release carbon dioxide while
absorbing the oxygen from the packaging, which is a reaction that preferably happens only when it is
required. This action offers protection and prolongs the shelf life of the food inside. It can be made to
operate at different temperatures (refrigeration or freezing) and a specific humidity [38].
The area of smart packaging is in full development and can provide solutions to reduce foodborne
diseases and also help to reduce environmental problems. Research in this field is growing, evolves,
and matures continuously, and smart packing is expected to improve food safety and quality soon.

4. Active Packaging
The concept of active food packaging is defined as innovative packaging that interacts with the
food and absorbs derived chemicals to prolong the shelf life and ensure safety and quality at the same
time. Active packaging creates a barrier between food and environmental space and stays in touch
with the food inside, offering protection [29]. An important characteristic of active packaging is the
capability of maintaining a low concentration in oxygen to slow the lipid oxidation. A low oxygen
atmosphere can be achieved by the incorporation of antioxidant compounds (that act as protectors
against oxidation processes) such as vitamins C and E [11], propolis, tocopherols, or plant extracts [29].
Overall, active packaging involves active compounds from different sources that can be in contact
with the food or can be incorporated in the coating material [8]. Active compounds should be safe for
Coatings 2020, 10, 550 7 of 26

human health; if combined active compounds are used, the mixture must be evaluated and authorized
by the European Food Safety Authority [25].

4.1. Nanomaterials
The latest trends in the active packaging industry are to develop new active materials for preventing
degradation and maintaining the quality for a longer time [28]. Good candidates to evolve in this
direction are nanomaterials given their mechanical, optical, thermal, and antimicrobial attributes [11].
Nano packaging materials have an advantage in the food industry due to the protection they
can assure against the foodborne pathogens as Escherichia coli, Staphylococcus aureus, and Salmonella,
which are known for food poisoning [39]. Researchers have claimed that nanotechnology can solve the
most common food poisoning symptoms such as fever, diarrhea, nausea, vomiting, and abdominal
pain, which can even cause death in the case of children, pregnant women, and old people [40–42].
According to many research papers, nano packaging can also come with solutions for reducing
environmental waste by using bionanocomposites (chitosan, starch, alginate, carboxymethyl cellulose,
pectin) [43–45]. To make biocomposite materials an efficient solution for the food packaging industry,
they should be improved for having high antimicrobial activity, better mechanical proprieties, and gas
barrier functions. These improvements are possible using nanotechnology and active and intelligent
packaging solutions [46]. A good mechanical amendment and antimicrobial activity for the most
common pathogens found present in food were identified as zinc oxide (ZnO) nanoparticles and
titanium dioxide (TiO2 ) nanoparticles [39,43]. Both biocompatible materials have been tested for their
efficacy against Salmonella typhi, Klebsiella pneumoniae, and Shigella flexneri. The results showed that
TiO2 and ZnO have inhibitory action against the bacteria mentioned above [39,47].

4.2. Polymers
The research on sustainability and the circular economy bring to the front the zero-waste processes
that require the re-integration of by-products as a priority for the zero-waste agenda [48]. In this
context, many studies have been made for developing new methods to integrate compounds extracted
from by-products in usual technologies, such as food packaging.
The most important fact is that those compounds can be recovered from food by-products,
such as seafood by-products (heads, gills, skin, trimmings) [49,50] for chitosan extraction, and fruit
and vegetable industries by-products (pumpkin seeds and peels, grapefruit peel, sunflower head,
sisal waste, pomegranate peel, eggplant peel, sour orange peel) for alginate and pectin [51–54].
They present high proprieties of biocompatibility, bioadhesion, and biodegradability, which is why
their applicability is persistently growing [44].
As a coating material, a mixture of chitosan with 0.5% apple peel polyphenols or chitosan–
proanthocyanidins combination has shown better mechanical proprieties and tensile strength [55,56].
Better flexibility and water resistance presented the films based on chitosan and grape seed extract or
chitosan and apricot kernel essential oil in a ratio of 1:1 [57,58]. The application of starch in the packaging
industry is limited by the disadvantage of reduced plasticity [59]. A mixture form by urea and ethanolamine
can act as a plasticizer to prepare thermoplastic starch and succeeds to growth its mechanical properties and
solve the issue of low plasticity [60]. Packaging mixtures presented behind do not cause environmental
problems, are biodegradable and not toxic, and can be obtained from sustainable sources [61,62].
Coatings 2020, 10, 550 8 of 26

4.3. Antioxidants
Polyphenols are parting from the class of phytochemicals, and they can be found in plant-derived
products such as coffee, tea, wine, fruits, vegetables, or chocolate [63,64]. They can be recovered from
plant residues such as peels, bran, husks, and skins, which usually are wasted in their processing [65,66].
Many studies highlight the benefits that polyphenols can bring to human health, beginning with the
preventive effects against cardiovascular disease [67–69], anti-inflammatory, anticoagulant, anticancer,
and antioxidant proprieties [70–76]. For those functions and others (e.g., the prebiotic effect [64]),
polyphenols are used in several areas such as drugs and the food industry or packaging area.
However, active packaging is still a studied area with great potential, which can improve the food
packaging industry considerably.

5. Intelligent Packaging
The food industry is in continuous progress and one of the most revolutionary concepts developed
Coatings 2020,
recently 10, x FOR PEER
is intelligent REVIEW [26]. Intelligent packaging can be represented by a small tag8 that
packaging of 24

is capable of monitoring the quality of food and can notice the consumer if there is a contamination
packaging has the advantage to communicate directly with the consumers through an incorporated
problem with the food product [77]. In comparison with active packaging, intelligent packaging has
device [78].
the advantage to communicate directly with the consumers through an incorporated device [78].
With the technology evolution, indicators used in intelligent packaging were classified into two
With the technology evolution, indicators used in intelligent packaging were classified into two
categories: indirect indicators and direct indicators, as presented in Figure 3. Researchers are now
categories: indirect indicators and direct indicators, as presented in Figure 3. Researchers are now
focused to develop more the second category (direct indicators) because of their ability to maintain
focused to develop more the second category (direct indicators) because of their ability to maintain
the quality of the product and also to give more targeted information about volatile compounds of
the quality of the product and also to give more targeted information about volatile compounds of
microbial origin, biogenic amines, toxins, or pathogenic bacterias [3].
microbial origin, biogenic amines, toxins, or pathogenic bacterias [3].

Figure 3. Food quality and safety indicators used in intelligent packaging.

Figure 3. Food quality and safety indicators used in intelligent packaging.
The latest consumer demands of the 21st century are the products that can help them saving time,
The latest consumer demands of the 21st century are the products that can help them saving
such as “ready-to-eat” and “heat and eat” meals. Another requirement registered is represented by
time, such as “ready-to-eat” and “heat and eat” meals. Another requirement registered is represented
the products’ microwavable, easy opening, reusable characteristics [79]. An easy-to-use food package
by the products’ microwavable, easy opening, reusable characteristics [79]. An easy-to-use food
label (Figure 4a) for pork was developed using pH indicators (bromocresol purple, bromothymol
package label (Figure 4a) for pork was developed using pH indicators (bromocresol purple,
blue, and a mixture of bromothymol blue and methyl red) for monitoring freshness and shelf life [80].
bromothymol blue, and a mixture of bromothymol blue and methyl red) for monitoring freshness
A self-adhesive label, named Fresh-Check (Figure 4b), was developed to ensure consumers about
and shelf life [80]. A self-adhesive label, named Fresh-Check (Figure 4b), was developed to ensure
the freshness of the perishable food products. “The active center circle of the Fresh-Check darkens
consumers about the freshness of the perishable food products. “The active center circle of the Fresh-
irreversibly, faster at higher temperatures and slower at a lower temperature”; in this way, consumers
Check darkens irreversibly, faster at higher temperatures and slower at a lower temperature”; in this
way, consumers can know for sure if the product is fresh or not [81]. Another study has developed
an on-package colorimetric sensor label (Figure 4c) for monitoring the ripeness of the apple after
packing. This sensor was able to detect the aldehyde emission, in solution or vapor, of apples based
on Methyl Red. As the apples mature, the sensor label changes its color in yellow, orange, and red in
Coatings 2020, 10, 550 9 of 26

can know for sure if the product is fresh or not [81]. Another study has developed an on-package
colorimetric sensor label (Figure 4c) for monitoring the ripeness of the apple after packing. This sensor
was able to detect the aldehyde emission, in solution or vapor, of apples based on Methyl Red. As9 the
Coatings 2020, 10, x FOR PEER REVIEW of 24
apples mature, the sensor label changes its color in yellow, orange, and red in the end [82].

(a) (b)

(c)
Figure4.4.(a)
Figure (a)Color
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However,
Intelligentcarefully
packaging watching
can givetheinformation
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about labels,
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of food inside andaspect to note the
can present is
that these labels used as indicators are in direct contact with the food, which can be dry (coffee,
entire lifecycle of the product beginning with packing and distribution up to selling [78,83]. It can be fruits,
and
used vegetables,
along withbakery ware), liquid
active packaging for (beer, beverage),
watching orof
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compounds and migration of
their efficacy.
compounds from food contact labels according to food safety needs to be tested agreeing to the
Intelligent packaging has a specific role: to improve safety and quality issues and to control the specific
European
traceabilitydirectives (Regulation
of the food 450/2009)
products. that
To fulfill regulate
this that active
task, systems and
such asintelligent packaging and
sensors, indicators, materials
Radio
require authorization [3].
Frequency Identification (RFID) are used [26].
Intelligent packaging can give information about the state of food inside and can present the
entire lifecycle
5.1. Sensors of the
Used product
in Food beginning with packing and distribution up to selling [78,83]. It can be
Packaging
used along with active packaging for watching the effect of the active compounds and their efficacy.
Sensors are one of the most studied electronic devices from the intelligent packaging field. Their
Intelligent packaging has a specific role: to improve safety and quality issues and to control the
main function is to detect and convert a signal form to another, using a transducer [19]. Sensors can
traceability of the food products. To fulfill this task, systems such as sensors, indicators, and Radio
be classified into active or passive sensors. If the transducer needs external power for measurement,
Frequency Identification (RFID) are used [26].
the sensor is active; if it measures without help, the sensor is passive [24]. A traditional sensor is
capable of measuring parameter changes such as temperature, pH, humidity, light exposure, or color
changes. Research is advancing in the improvement of chemical sensors that can monitor package
integrity and food quality and safety [19,24,84]. Among the chemical sensors found in the scientific
literature are those detecting volatile organic compounds, compounds with high sensitivity, and gas
molecules (H2, CO, NO2, O2, H2S, NH3, CO2, CH4), which have high importance to the food sector
[24].
Biosensors are part of chemical sensors that differ by the biological components used as detectors
such as cells, antibodies, bacteria, yeast, fungi, plant and animal cells, biological tissue or enzymes,
which are obtained by isolation and purification from biotechnological processes [24]. The most
successful type of biosensor is the glucose sensor for diabetics, which is from the medical part, but
they are found also in the pharmaceutical industry, food and process control, environmental
monitoring, defense, and the security area [85].
In the intelligent packaging industry, chemical sensors, biosensors, and others can be used and
incorporated in films. Flex Alert Company Ltd. with Vancouver-based partners has developed a
commercially available biosensor that is capable of detecting pathogens (E. coli, Salmonella, and
aflatoxins) in coffee beans, dried nuts, seeds, wine barrels, and fresh fruit. An active biosensor, using
Coatings 2020, 10, 550 10 of 26

5.1. Sensors Used in Food Packaging

Sensors are one of the most studied electronic devices from the intelligent packaging field.
Their main function is to detect and convert a signal form to another, using a transducer [19].
Sensors can be classified into active or passive sensors. If the transducer needs external power for
measurement, the sensor is active; if it measures without help, the sensor is passive [24]. A traditional
sensor is capable of measuring parameter changes such as temperature, pH, humidity, light exposure,
or color changes. Research is advancing in the improvement of chemical sensors that can monitor
package integrity and food quality and safety [19,24,84]. Among the chemical sensors found in the
scientific literature are those detecting volatile organic compounds, compounds with high sensitivity,
and gas molecules (H2 , CO, NO2 , O2 , H2 S, NH3 , CO2 , CH4 ), which have high importance to the food
sector [24].
Biosensors are part of chemical sensors that differ by the biological components used as detectors
such as cells, antibodies, bacteria, yeast, fungi, plant and animal cells, biological tissue or enzymes,
which are obtained by isolation and purification from biotechnological processes [24]. The most
successful type of biosensor is the glucose sensor for diabetics, which is from the medical part, but they
are found also in the pharmaceutical industry, food and process control, environmental monitoring,
defense, and the security area [85].
In the intelligent packaging industry, chemical sensors, biosensors, and others can be used and
incorporated in films. Flex Alert Company Ltd. with Vancouver-based partners has developed
a commercially available biosensor that is capable of detecting pathogens (E. coli, Salmonella,
and aflatoxins) in coffee beans, dried nuts, seeds, wine barrels, and fresh fruit. An active biosensor,
using wireless communication, alerts manufacturers, consumers, and distributors to some toxin
presence by sending information in real-time during storage and in packaged products [86].
Following the potential of sensors in the food industry, it can be seen that they may be a solution
for combating food waste and also for reducing the risk of diseases caused by altered foods.

5.2. Indicators Used in Food Packaging

Indicators are part of the intelligent packaging group of devices. They have a different method of
action than sensors do, by providing immediate qualitative visual information such as color change,
color intensity change, or diffusion of colors, which are irreversible changes about the product [24,87].
Indicators are the most commonly used in commercial form, and a few of them are presented in Table 3.
Coatings 2020, 10, 550 11 of 26

Table 3. Commercially available indicators for intelligent packaging.

Type Trade Name Manufacturer Information Reference

- aims to alert consumers, producers, or sellers if the integrity of the packaging is

O2 Sense Freshpoint Lab damaged by detecting oxygen inside, which can lead to the degradation of quality [24,87,88]
and safety of the product inside.
- the indication is based on a color change.
Insignia Technologies - specially made for products packed in plastic material, in a controlled atmosphere.
Novas [24,87]
Ltd. - when the packaging is degraded, the pigment used as an indicator changes its color.
Gas indicators

Mitsubishi Gas - an in-packaging indicator that monitors the presence/absence of oxygen.

Ageless Eye - if the oxygen level is 0.1% or less, the color of the indicator is pink; when the oxygen [88–91]
Chemical Inc.
level attains 0.5% or more, the color indicated will be blue.

- fish and seafood products are emitting a special odor (caused by volatile amines)
when they lose their freshness.
Freshtag COX Technologies - the dye-based indicator interacts with the odor-causing chemicals and produces a [24,92]
change color reaction.
Freshness indicator - the intense pink color created indicates the lack of freshness.

DSM NV and Food - it is placed inside of the packaging.

Sensorq Quality Sensor - is applied for meat and poultry products. [87,93]
International - detect the gaseous by-products of bacterias that cause food poisoning.

- it monitors time and temperature for products where temperature can be a critical
control point.
- the adhesive label is applied to the food packaging and once that is activated, it starts
Timestrip Timestrip UK Ltd. to monitor the temperature (days, weeks or months). [87,94]
- the device records the time when the temperature recommended was not respected.
- it is applicable for fresh seafood, fresh produce, airline catering, school meals, home
delivery diets, food retailing, restaurants, hub, and spoke production.
Time-temperature - it is used as part of the secondary packaging and monitors the storage and
transportation condition.
- it is an adhesive label that easily attaches to the packaging and visually shows
Monitormark 3M exposure and relative time over which exposure happened. [19,87,95,96]
- it has an irreversible action, even if the temperature during storage or delivery returns
to a normal value.
- it is applied for food products such as bakery, beverage, confectionery, and meat
products that have critical temperature points beginning with –15 to 26 ◦ C.
Coatings 2020, 10, 550 12 of 26

Table 3. Cont.

Type Trade Name Manufacturer Information Reference

- the system monitors the freshness of a food product and is specially made for products
sensitive to temperature.
Ciba Specialty - after the label is activated, it becomes dark and then grows progressively lighter with time if
Onvu Chemicals and the temperature rises. [97,98]
FreshPoint - the product has reached the end of the shelf life when the color reaches the reference
color tone.
- is commercially available for products as meat, fish, and dairy products with a shelf life of 5–6
days at 5 ◦ C.

- specially made for seafood products and is improved for the recognition of Clostridium
Botulinum toxin formation;
- the second most common pathogen (25%) in seafood is Clostridium Botulinum, and its growth
and multiplication are directly influenced by temperature, for example, at 60 ◦ F,
multiplication is 10–12 times more rapid than at 40 ◦ F or at 72 ◦ F, it is even 25–27 times more
L5-8 Smart rapid than at 40 ◦ F.
TTI Seafood Vitsab - this label is based on an enzymatic reaction, which is given by the enzyme mix and substrate [24,99,100]
Label from the center of the label; the mixture is activated by applying moderate pressure on the
“window” and is recognized by a homogenous green color in the “window”.
- the shade of green color can be changed in four ways (25%, 40%, 65%, 85%), and this is
correlated with the ending of the product’s validity.
- if the green color changes and is replaced by an orange color (100%) or red (120%), it means
Time–temperature that the product is no longer safe for consumption.
indicators
- it comes in the form of a cardboard tag.
- the label contains a purple color chemical indicator (chromium–chloride complex) which, at
Cook-Chex Pymah Corp various conditions of time and temperature in a pure steam atmosphere, changes its color [87,101]
to green.
- this type of indicator is used commercially to verify the sterilization or autoclaving operation
in the canning industry.

- it is a visual indicator that undergoes color changes after exposure at a higher temperature
than the one established by the manufacturer.
- the speed of changing the color of the indicator (from silver to white) increases directly in
proportion to the increase in the temperature of the product’s the environment.
Evigence EVIGENCE - indicator labels can be calibrated for products with a shelf life from some hours to [102,103]
sensors SENSORS several years.
- labels are improved so that their application and activation is automatically done on the food
packaging line.
- using the SMART DOTTM app for mobile, consumers can scan the label before, during, and
post-acquisition, for having more details (the remaining shelf life, time to repurchase).
Coatings 2020, 10, 550 13 of 26

Table 3. Cont.

Type Trade Name Manufacturer Information Reference

Time–temperature - monitors the food in the store or at home.

indicator/freshness Fresh-Check Temptime Corp - it is an adhesive label, which has a central reactive part, represented by a circle; the circle [19,104]
indicator darkens at an accelerated rate if the product is not stored at the appropriate temperature, and
consumers can see the freshness of the food products in real time.

- a waterproof and self-adhesive label that irreversibly changes its color depending on the
Thermostrip LCR HALLCREST temperature of dishware in dishwashers. its main purpose is to indicate if the proper
Disinfection Indicator dishwasher temperature has been reached for sanitation. [105]
DL LLC
- it can be used also as proof for HACCP (Hazard Analysis and Critical Control Point). The
temperature range covered by the indicator is beginning with 29 to 290 ◦ C.
Coatings 2020, 10, 550 14 of 26

5.3. Radio Frequency Identification

Radio Frequency Identification (RFID) is an automatic identification technology based on remote
data storage and retrieval using devices named labels, which are improved with wireless sensors for
product
Coatings identification.
2020, 10, x FOR PEERThe RFID system is made of specific elements presented in Figure 5. 13
REVIEW Inofthe
24
food industry, RFID technology is part of the intelligent packaging sector. An RFID tag tracks food
traceability
Coatings in xreal
2020, 10, FORtime
PEERand monitors the entire cold chain for food applications (e.g., intercontinental
REVIEW 13 of 24
fresh fish logistic chain) [106].
MEMORY
MICROCYP

system
MEMORY
system MICROCYP
READER
ANTENNA
RFID
READER
ANTENNA
RFID

PACKAGING

PACKAGING

Figure 5. Radio Frequency Identification system elements.

Figure 5. Radio Frequency Identification system elements.

RFID Figure 5. Radio Frequency Identification system elements.

RFID tags
tagscancanbebepart
partofoftwo
twocategories,
categories,passive
passiveand active
and activetags; thethe
tags; category depends
category dependson theon use
the
or not of external or integrated batteries for the transfer of information in the memory
use or not of external or integrated batteries for the transfer of information in the memory microchip. microchip.
RFID
Passive tagsare
tags canusing
be parta of two categories,
magnetic passivebetween
and active
thetags; the category depends on the use
Passive tags are using a magnetic fieldfield created
created between the reader reader
antenna antenna
and tag; and
thus,tag; thus, the
the intelligent
or not of
intelligentexternal
tag takes or integrated
the energy batteries
and for
transfers the
the transfer
encoded of
data information
to the memoryin the memory
chip of the microchip.
label. Active
tag takes the energy and transfers the encoded data to the memory chip of the label. Active RFID
Passive
RFID tags
tags areare using
using a magnetic
batteries field created
for energy betweenthethe reader antennathe and tag; thus, the
the
tags are using batteries for energy powerpower
to make to the
make
circuit circuit
between between microchip
the microchip and theand reader
intelligent
reader tag takes the energy and transfers the encoded data to the memory chip of the label. Active
antennaantenna [87]. back
[87]. Taking Taking backprinciples,
to first to first principles,
the working theprocess
working process
of the RFIDofsystem
the RFID system in
is explained is
RFID tags in
explained areFigure
using6.batteries for energy power to make the circuit between the microchip and the
Figure 6.
reader antenna [87]. Taking back to first principles, the working process of the RFID system is
explained in Figure 6.

Data stored in
tags are
activeted by the
Datareader
stored in
tags are
activeted by the
reader
Readers are
decoding the data
and transfer the
Readers are
information to a
decoding
computerthe data
system
and transfer the
information to a
computer system

Computer system
is further
processing the
Computer system
information
is further
processing the
information

The working
Figure 6. The working principles
principles of
of an
an RFID system.

Therefore, RFID
Therefore, RFID tags
tags can
can increase
Figure the efficiency
6. The the
increase efficiency
working of supply
principles
of supply chains
of an RFID and provide
system.
chains and provide suppliers
suppliers with
with an
an
advanced method
advanced method of
of food
food product
product monitoring
monitoring until
until they
they become
become available
available to
to consumers.
consumers.
Therefore, RFID tags can increase the efficiency of supply chains and provide suppliers with an
advanced
6. method of
Food Packaging food product monitoring until they become available to consumers.
Materials

6. Food
6.1. Packaging
Typical Materials
Packaging Materials
Since the
6.1. Typical Industrial
Packaging Revolution from the 18th–19th century, industries had lost the value of
Materials
reusing the packaging or the packaging material [24]. Over the years, this fact caused unwanted
Coatings 2020, 10, 550 15 of 26

6. Food Packaging Materials

6.1. Typical Packaging Materials

Since the Industrial Revolution from the 18th–19th century, industries had lost the value of
reusing the packaging or the packaging material [24]. Over the years, this fact caused unwanted
waste, which created much damage to the environment. The Food and Agricultural Organization of
Coatings 2020, 10, x FOR PEER REVIEW 14 of 24
the United Nations (FAO) made a short report and a SWOT (Strengths, Weaknesses, Opportunities,
and Threats)
and Threats) analysis
analysis of of the
thefood
foodpackaging
packagingindustry
industryinindeveloping
developingcountries.
countries.They
Theyhave
havepresented
presenteda
aglobal
globalview
viewofofthis
thisindustry,
industry,with
withspecial
specialattention
attentionininits
itssize,
size,structure,
structure,and
andthe
thematerials
materials used.
used. The
The
most applied materials for packing are represented by paper, rigid plastic, metal,
most applied materials for packing are represented by paper, rigid plastic, metal, and glass, and glass, as as
seen
seenin
Figure 7 [4].
in Figure 7 [4].

The most applied materials for food packaging

40%
34%
35%
30% 27%
25%
20%
15%
15% 11%
10%
5%
0%
paper plastic metal glass

Figure
Figure 7.
7. The
The most
most applied
applied materials
materials for
for food
food packaging
packaging (Data Sources from Ref. [4]
(Data Sources [4]).).

In 2015, an amount of 322 M tons of plastic waste was registered, of which 49 M tons was from
the food packaging industry [43]. Packaging
Packaging materials
materials used
used in
in the
the modern
modern era
era such
such as
as glass,
glass, metals,
metals,
paper, plastic, and alternative biomaterials
biomaterials are presented in Table 4 with their advantageous and
disadvantageous characteristics.

Table 4. The advantages and disadvantages of typical and alternative packagings.

Advantage Disadvantage References

Typical Packaging Materials
Inorganic and chemically inert;
Transparent, recyclable and it does not
pollute;
Easy to model; High manufacturing temperatures;
It can be sterilized at high Big energy consumption at
temperatures; manufacturing;
Glass [1,13]
It offers protection against water and High net mass;
gas vapor; Breaks easily and it is
It does not deteriorate by oxidation or nonbiodegradable.
other forms;
It does not react with food or the
environment.
It is a barrier to gasses and humidity;
It can be sterilized and it is recyclable;
Metals (steel, tin, Covers a larger area of the food
Has high costs of manufacturing;
chromium, and industry; [1,13]
Energy intensive;
aluminum) Low toxicity;
Good mechanical strength and
resistance to working.
Low costs, low weight, recyclable, and
biodegradable; Barriers to moisture and vapor are
Paper and cardboard The resulting wastes can be reused for weak; [1,13]
energy recovery; Shock protection is low.
It has good printing properties.
Coatings 2020, 10, 550 16 of 26

Table 4. The advantages and disadvantages of typical and alternative packagings.

Advantage Disadvantage References

Typical Packaging Materials
Inorganic and chemically inert;
Transparent, recyclable and it does not pollute;
Easy to model; High manufacturing temperatures;
It can be sterilized at high temperatures; Big energy consumption at manufacturing;
Glass [1,13]
High net mass;
It offers protection against water and gas vapor; Breaks easily and it is nonbiodegradable.
It does not deteriorate by oxidation or other forms;
It does not react with food or the environment.
It is a barrier to gasses and humidity;
Metals (steel, tin, It can be sterilized and it is recyclable;
Has high costs of manufacturing;
chromium, and [1,13]
Covers a larger area of the food industry; Energy intensive;
aluminum)
Low toxicity;
Good mechanical strength and resistance to working.
Low costs, low weight, recyclable, and biodegradable;
Barriers to moisture and vapor are weak;
Paper and cardboard The resulting wastes can be reused for energy recovery; [1,13]
Shock protection is low.
It has good printing properties.
Economically efficient; Replaces glass, metal, and paper packaging;
Pollute the soil;
Plastic Good mechanical properties and a barrier to [1,13]
It is not degradable and harms marine life;
gasses and humidity;
The debris cannot be eliminated and can be
It is flexible, transparent, or can be colored. ingested from seafood.
Alternative Packaging Materials
Coatings 2020, 10, 550 17 of 26

Table 4. Cont.

Advantage Disadvantage References

Non-toxic and biodegradable;
Environmental friendly;
Antimicrobial and bacteriostatic proprieties;
Chitosan-based biofilms Restricted scope. [13,107–109]
Preserve the taste;
Improve physical, mechanical, and chemical properties;
Maintain tissue firmness; inhibit the increase of respiration rate.
Frequency in nature, renewable;
High water solubility;
Environmentally friendly; Insufficient water barrier properties;
Starch-based biofilms [1,59,107,110]
Weak mechanical properties;
Low cost, non-toxic;
Reduced plasticity.
Biodegradable;
Suitable for foods with low humidity (confectionery and biscuit
trays).
Good properties of permeability;
Films and coatings based Color stability;
Low surface tension. [111,112]
on mango by-product
Antioxidant activity;
Hydrophobicity;
Decreases in manufacturing cost.
 Suitable for foods with low humidity Reduced plasticity.
(confectionery and biscuit trays).
Good properties of permeability;
Films and coatings Color stability;
based on mango by- Antioxidant activity; Low surface tension. [111,112]
product Hydrophobicity;
Coatings 2020, 10, 550 18 of 26
Decreases in manufacturing cost.

6.2.Alternative
6.2. AlternativeMaterials
Materials
Alternativebiomaterials
Alternative biomaterialscan
canrefer
refer to
to different
different compounds
compounds(e.g.,
(e.g.,poly-lactic
poly-lacticacid,
acid,starch, cellulose)
starch, cellulose)
incorporated in coating materials. The most important aspect of the food industry is the material used
incorporated in coating materials. The most important aspect of the food industry is the material used
for packaging. To solve the issues of plastic pollution caused by the food packaging or pharmaceutical
for packaging. To solve the issues of plastic pollution caused by the food packaging or pharmaceutical
industries, the researchers on this domain are focused on finding alternatives packaging solutions
industries, the researchers on this domain are focused on finding alternatives packaging solutions [43].
[43].
The latest trends are to use bioplastic such as biopolymers and also plant extract incorporated
The latest trends are to use bioplastic such as biopolymers and also plant extract incorporated
for their antimicrobial properties [107]. Natural biodegradable polymers are obtained in a
for their antimicrobial properties [107]. Natural biodegradable polymers are obtained in a complex
complex metabolic process. Biopolymers belong to the class of proteins, polysaccharides, lipids,
metabolic process. Biopolymers belong to the class of proteins, polysaccharides, lipids, phenolic
phenolic compounds,
compounds, and other and other and
classes, classes,
theyandcan they can be extracted
be extracted fromor
from biomass biomass
obtained orfrom
obtained from the
the vegetal,
vegetal,
animal,animal, or microbial
or microbial sourcessources presented
presented in Figurein8Figure
[45]. 8 [45].

Coatings 2020, 10, x FOR PEER REVIEW 16 of 24

Figure8.8. Classification
Figure Classification of natural
natural biodegradable
biodegradablepolymers.
polymers.
Starch is one of the most used natural biodegradable polymers at the moment, and it is being
Starch
part of is one of the most
the carbohydrates class;used natural biodegradable
its chemical polymers
structure is presented inat the moment,
Figure and important
9. The most it is being
part of the
sources of carbohydrates
starch are cereals class; its chemical
(wheat, rice, corn)structure is presented
and tubers (potato)in [107,113].
Figure 9. The most
Starch important
contains two
sources of starch
fundamental are cereals
compounds: (wheat,which
amylose, rice, corn) and tubers
is responsible for(potato) [107,113].
the structure and theStarch
rigidcontains two
proprieties,
fundamental
and compounds:
amylopectin, which helpsamylose, whichthrough
digestion is responsible for the
its precise structuresuch
functions and asthethe
rigid proprieties,
enhancing of
and amylopectin,
solubility which helps
of the polymer [114].digestion
More than through
this, its precise
using functions biofilms
starch-based such as theis enhancing
offering foodof solubility
package
of the polymer
antioxidant [114]. especially
activity, More thanifthis, using
gallic acidstarch-based
is added, 0.3biofilms is offering
g/g starch [110]. Afood packageReview
Systematic antioxidant
and
activity, especially if gallic acid is added, 0.3 g/g starch [110]. A Systematic Review
Meta-Analysis has also shown recently the potential of using potato starch in the development of and Meta-Analysis
has also shown
biofilms used forrecently
food the potentialbecause
packaging of usingitpotato
is an starch
importantin theraw
development of biofilms
material derived from used for
many
food packaging
industries such asbecause it isvegetable
fruits and an important raw material
processing, derived
has a low cost, from
and ismany industries
the most wealthy such as fruits
biomaterial
and vegetable processing, has a low cost, and is the most wealthy biomaterial [115].
[115].

Figure 9.
Figure Chemical structure
9. Chemical structure of
of polymeric
polymeric starch.
starch.

Carotenoids are a part of the lipophilic pigment class. The most well-known sources are red,
yellow, and orange fruits and vegetables, especially carrots, tomato, watermelon, and some species
of fish such as salmon and crustaceans, principally cooked lobster and crab [61,116]. In addition to
other pigments such as chlorophyll, β-carotene, anthocyanins, and lycopene, which are presented in
Coatings 2020, 10, 550 19 of 26

Carotenoids are a part of the lipophilic pigment class. The most well-known sources are red,
yellow, and orange fruits and vegetables, especially carrots, tomato, watermelon, and some species
of fish such as salmon and crustaceans, principally cooked lobster and crab [61,116]. In addition to
other pigments such as chlorophyll, β-carotene, anthocyanins, and lycopene, which are presented in
Figure 10, β-carotene is added in the composition of biofilms used to make food packaging. The great
attention of the researchers received the importance of β-carotene for its proprieties of excellent natural
Coatings 2020, 10, x FOR PEER REVIEW 17 of 24
antioxidant and colorant products [117]. The encapsulation of β-carotene is used for obtaining active
biodegradable
a temperature packaging
variation infilms. The presence
intelligent of β-carotene
packaging due to thehas provedof
property better thermal
changing its protection for the
color depending
packaging films and greater
on the temperature [34,120]. protection against the oxidation process [61]. A recent study has developed
a poly-lactic
Anotheracid (PLA) compound
bioactive film with three
fromdifferent compositions,
the pigment class withusing
high lycopene,
antioxidant β-carotene, andcan
activity that bixin.
be
The standard curves of the three compounds were made in the following concentrations:
incorporated in active packaging is lycopene [116]. The most known natural sources are tomatoes, β-carotene
(λmax = 449
especially thenm), from
peels 2.2 to
[121], but105.4 µgbe
it can
−1 (R2 = 0.999); lycopene (λmax = 480 nm), from 0.3 to 13.9 µg
mLfound also in guava or papaya [122]. An important aspect is
mL −1 (R2 = 0.999); bixin (λmax = 457 nm), from 0.3 to 5.3 µg mL−1 (R2 = 0.996). All types were destined
that lycopene can be extracted from the tomato product waste [123]. A study shows that tomato
for sunflower
processing oil oxidation
by-products protection
contain up to[118].
0.1%Thelycopene
carotenoids
andwere
otherprogressively released to the
bioactive compounds suchfood
as
simulant, the attainment of approximately 45% release of β-carotene and lycopene,
tocopherols and other carotenoids [124]. A research paper presented a method to replace synthetic and approximately
55% release
oil-based of bixin.with
stabilizers The naturals
PVA films improved compounds
antioxidants with β-carotene and lycopene
obtained from tomato haveandproved
grapea seeds
good
barrier against light and oxygen, and PVA
recovered from the tomato and wine industries [125]. films with bixin presented the best antioxidant activity for
sunflower oil [118].

Figure 10. Bioactive pigments and their chemical structure.

Figure 10. Bioactive pigments and their chemical structure.
Intelligent and active packaging has been obtained by poly(vinyl alcohol) (PVA) films mixed with
By-products
chitosan, can and
itaconic acid, be recovered from food
tomato by-products waste,
extract which
(TBE) represents
[117]. a high-value
TBE was used in anothersource of
research
functional
study components
as a natural pigment such
due as proteins,
to its fibers,
carotenoid polysaccharides,
content phytochemicals,
[119]. TBE is rich lipids, and
in carotenoids (lutein, fatty
lycopene,
acidsβ-carotene),
and [126]. Onean ofcontent
the best-known by-products
of 3.273 mg/100 g DW, and thatphenolic
is very compounds
frequently used in the acid–glucoside
(e.g., caffeic world is bran
resulting5-caffeoy
isomer, from thelquinic
grain acid,
industry. Bran has a low price,
quercetin-diglucoside), the great availability,
total content and mg/100
of 80.596 multipleg functional
DW [117].
proprieties
This (antioxidant
active film has provenand anti-inflammatory
to have increased physical activity) due(diameter,
properties to the high content
thickness, of phenolic
density, weight),
compounds,
inhibition fibers,
effects and minerals
against bacterias[127].
such as S. aureus and P. aeruginosa, and antimicrobial activity to
A by-product
S. aureus, that can be
E. coli, P. aeruginosa, used from
S. enterica the winery
Enteritidis, and S.waste is Typhimurium
enterica grape marc. [128].
[117]. Globally, the
production of grapes,
The literature achieved
shows in 2017 an amount
that chlorophyll of more than
is recommended 77,000
to be used tons
as a and only the temperature
colorimetric pulp is used
indicator for 50 to 70 degrees in chitosan films, along with anthocyanin, which is capable ofepicatechin,
for the wine production. The rest (seeds and peels) forms the grape marc abundant in detecting a
catechin, gallic
temperature acid, procyanidins,
variation and phenolic
in intelligent packaging dueacids,
to the which
propertymakes it have its
of changing good antioxidant
color dependingandon
antimicrobial
the temperature activity [129].
[34,120].
Globally, banana production is registering an amount of 102 tons annually, of which 35% is only
the peel, which is considered waste. One study developed an antioxidant chitosan biofilm improved
with banana peels extract, which is fraught in bioactive compounds. The active biofilms were
particularly made for maintaining the postharvest quality of apple during storage [109]. The by-
product of mango is another example of a fruit that is used for developing active films for the food
packaging industry. The seeds of mango had a large concentration of bioactive compounds, while
Coatings 2020, 10, 550 20 of 26

Another bioactive compound from the pigment class with high antioxidant activity that can be
incorporated in active packaging is lycopene [116]. The most known natural sources are tomatoes,
especially the peels [121], but it can be found also in guava or papaya [122]. An important aspect is that
lycopene can be extracted from the tomato product waste [123]. A study shows that tomato processing
by-products contain up to 0.1% lycopene and other bioactive compounds such as tocopherols and
other carotenoids [124]. A research paper presented a method to replace synthetic oil-based stabilizers
with naturals antioxidants compounds obtained from tomato and grape seeds recovered from the
tomato and wine industries [125].
By-products can be recovered from food waste, which represents a high-value source of functional
components such as proteins, fibers, polysaccharides, phytochemicals, lipids, and fatty acids [126].
One of the best-known by-products that is very frequently used in the world is bran resulting from
the grain industry. Bran has a low price, great availability, and multiple functional proprieties
(antioxidant and anti-inflammatory activity) due to the high content of phenolic compounds, fibers,
and minerals [127].
A by-product that can be used from the winery waste is grape marc. [128]. Globally, the production
of grapes, achieved in 2017 an amount of more than 77,000 tons and only the pulp is used for the
wine production. The rest (seeds and peels) forms the grape marc abundant in epicatechin, catechin,
gallic acid, procyanidins, and phenolic acids, which makes it have good antioxidant and antimicrobial
activity [129].
Globally, banana production is registering an amount of 102 tons annually, of which 35% is only the
peel, which is considered waste. One study developed an antioxidant chitosan biofilm improved with
banana peels extract, which is fraught in bioactive compounds. The active biofilms were particularly
made for maintaining the postharvest quality of apple during storage [109]. The by-product of mango
is another example of a fruit that is used for developing active films for the food packaging industry.
The seeds of mango had a large concentration of bioactive compounds, while the peel is rich in
polysaccharides. The film created present good properties of permeability, color stability, antioxidant
activity, and greater hydrophobicity [112].

7. Future Perspectives
Intelligent food packaging is an area with great potential for increasing the food packaging
sector, providing fast, inexpensive, and efficient ways to monitor the environmental conditions of
food in the supply chain. The next generation of food packaging developments and food packaging
materials must be more environmentally friendly, and more importantly, they should be reusable,
easy to use, and communicative with the consumers, to avoid the specific problems related to food
waste, food quality managing, or foodborne diseases. For all this to become possible, supplementary
attention should be driven to the innovative packaging and materials. Furthermore, recent strategies
involving agro-industrial by-products showed that numerous bioactive compounds can be recovered
and integrated into functional food packaging. Overall, future studies will be made on this topic with
the purpose of continuing evolution in the food packaging industry.

8. Conclusions
This review paper presents the most important aspects associated with active and intelligent
packaging and highlights many bioactive compounds recovered from agro-industrial by-products
that may be useful in active or intelligent packaging. Smart packaging has a strong impact on
food quality and control by allowing consumers to directly interpret the freshness and safety of the
food inside. Intelligent packaging is an improved version of active packaging, simply by including
devices from indicators and sensors classes for increased accuracy. The next future research can be
made for by-product compounds integration in the elements of smart packaging (e.g., indicators,
sensors) or for the design of new concepts of smart packaging that includes recovered bioactive
compounds. Nevertheless, the trend of zero waste and the efforts made in the world of science
Coatings 2020, 10, 550 21 of 26

to find environmentally friendly solutions to combat food waste and to capitalize raw materials at
high capacity is constantly growing; accordingly to this tendency, shortly, more compounds will be
integrated into food coatings.

Funding: This research was funded by a grant of the Romanian National Authority for Scientific Research and
Innovation, CCDI-UEFISCDI, project No. 27/2018 CO FUND–MANUNET III-NON-ACT-2, within PNCDI III and
the publication was supported by funds from the National Research Development Projects to finance excellence
(PFE)-37/2018–2020 granted by the Romanian Ministry of Research and Innovation.
Conflicts of Interest: The authors declare no conflict of interest.

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