Yadanabon University Research Journal 2016, Vol.7, No.

Utilization of Fruit Waste (Pineapple Peel) for Vinegar Production

Khin Hnin Aye*, Thwe Linn Ko**

Abstract

Pineapple peel which is usually discarded during the processing or consumption of the fruit was
used as a starting material to produce vinegar by two successive fermentations: alcoholic and
acetic acid fermentations. In alcoholic fermentation, pineapple peel was allowed to ferment for
conversion of sugar to ethanol by using baker yeast (Saccharomyces cerevisae). In acetic acid
fermentation, the conversion of ethanol to vinegar was carried out by acetic acid bacteria
(Acetobacteraceti) with continuous aeration. The vinegar was prepared by varying the amount
of yeast, amount of sugar, amount of yeast nutrient (ammonium phosphate) and time of
fermentation. Characteristics of prepared vinegar such as total solid content, alcohol content, pH
and acidity were determined in this work. The conversion of pineapple peels (food waste) to
vinegar (useful product) will minimize environmental pollution while producing value added
product, preserving vital nutrients of our foods and bringing down the cost of production of
processed foods.

Keywords: Pineapple Peel, Vinegar, Fermentation.

*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.
Yadanabon University Research Journal 2016, Vol.7, No.1

1. INTRODUCTION

Vinegar may be defined as a condiment made from various sugary and starchy
materials by alcoholic and subsequent acetic acid fermentation. Vinegar can be produced
by different methods and from various raw materials. Wine (white, red, and sherry
wine), cider, fruit musts, malted barley, or pure alcohol are used as substrates. Vinegar
production ranges from traditional methods employing wood casks and surface culture to
submerged fermentation in acetators. Vinegar traditionally has been used as a food
preservative. Whether naturally produced during fermentation or intentionally added,
vinegar retards microbial growth and contributes sensory properties to a number of foods
(Tan, 2005).

Vinegar plays an important role in salad dressings, ketchup, hot sauce and other
sauces. This needs industrial fermentation systems capable of producing a large amount
of vinegar. Many techniques have been developed to improve industrial production of
vinegar. Today, the most common technology for the vinegar industry is based on the
submerged culture with diverse technical modifications which try to improve the general
fermentation conditions (aeration, stirring, heating, etc.,) (Tan, 2005).

Vinegar making depends on two fermentation processes. The first is

transformation of sugar into alcohol and carbonic acid gas by yeast. The second is the
conversion of the alcohol into acetic acid (vinegar). Any substance containing 10% or
more sugar, or a substance easily change to sugar, or any fermented liquid containing 4%
or more alcohol can be made into vinegar. Waste fruit, inferior honey and other sugar
containing materials not suitable for sale or use, can often be made into satisfactory
vinegar. The waste cores and peels from canneries, and fruit driers can be turned to profit,
in this way (Sandar Aye, 2014).

Pineapple peels as agricultural wastes represent around 35% of the whole fruit
mass. If these wastes are discharged to the environment untreated, they could cause a
serious problem. So, it is necessary to have recycled waste raw material into useful

*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.
Yadanabon University Research Journal 2016, Vol.7, No.1

product of higher value added products or even as a raw material for other industries or
for use as food or feed after biological treatment (SweSwe Aung, 2013).

This research is aimed to produce low cost vinegar (useful product) from
pineapple peels (waste) which is usually discarded during the processing of fruit. The
conversion of fruit wastes into vinegar will help to enhance food security as well as to
reduce environmental pollution.

2. MATERIALS AND METHODS

2.1 Raw Materials
For the preparation of vinegar, pineapple peels were collected from pineapple
vendors. The yeast, Saccharomyces cerevisiaeand ammonium phosphate were purchased
from Kemiko Chemical Sale Centre, Yangon. The sugar used for this research work was
purchased from local market.

2.2 Preparation of Pineapple Peel Vinegar

Pineapple peels were thoroughly washed with water to remove impurities, and cut
into thin strips. Prepared pineapple peels (180 g), sugar (20 g) and distilled water (800 ml)
were put into the sterilized bottle. This is then followed by the addition of yeast (2.5 g) and
yeast nutrient (ammonium phosphate) (4g). The fermenter was then corked and sealed with
adhesive tape. The fermentation was allowed to take place at room temperature for two
days. After two days, alcohol was first formed by yeast. Then the residue was filtered and
the filtrate was covered with cheesecloth to allow Acetobacter to come in by chanced
approach method. This was then allowed to ferment for two weeks. At the end of the
fermentation process, the prepared vinegar was filtered, pasteurized and bottled.

2.2.1 Determination of Acidity by Varying the Amount of Sugar in the Preparation

of Pineapple Peel Vinegar
The same procedure as described in section (2.2) was carried out by varying the
amount of sugar, i.e., (10, 20, 30, 40, 50 and 60 g) respectively, while keeping the
following contents, the amount of pineapple peel (180 g), the volume of distilled water
*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.
Yadanabon University Research Journal 2016, Vol.7, No.1

(800 ml), the amount of yeast (2.5 g) and the amount of yeast nutrient (ammonium
phosphate) (4g). The results obtained are shown in Table (2.1).

2.2.2 Determination of Acidity by Varying the Amount of Yeast in the Preparation

of Pineapple Peel Vinegar
The same procedure as described in section (2.2) was carried out by varying the
amount of yeast, (i.e., 2, 2.5, 3, 3.5, 4 and 4.5 g) respectively, while keeping the
following contents, the amount of pineapple peel (180 g), the volume of distilled water
(800 ml), the amount of sugar (20 g) and the amount of yeast nutrient (ammonium
phophate) (4 g). The results obtained are shown in Table (2.2).

2.2.3 Determination of Acidity by Varying the Amount of Yeast Nutrient

(Ammonium Phosphate) in the Preparation of Pineapple Peel Vinegar
The same procedure as described in section (2.2) was carried out by varying the
amount of yeast nutrient (ammonium phosphate), (i.e., 3, 4, 5, 6 and 7 g) respectively,
while keeping the following contents, the amount of pineapple peel (180 g), the volume
of distilled water (800 ml), the amount of sugar (20 g) and the amount of yeast (2.5g).
The results obtained are shown in Table (2.3).

2.2.4 Determination of Acidity at Various Fermentation Periods in the Preparation

of Pineapple Peel Vinegar
The same procedure as described in section (2.2) was carried out by varying the
fermentation periods, i.e., (2, 4, 6, 8, 10and 12 weeks) respectively, while keeping the
following contents, the amount of pineapple peel (180 g), the volume of distilled water
(800 ml), the amount of sugar (20 g) and the amount of yeast (2.5 g) and the amount of
yeast nutrient (ammonium phosphate) (4 g). The results obtained are shown in Table
(2.4).

2.3 Analysis of Vinegar

The properties of prepared vinegar from pineapple peel such as acidity, pH,
alcohol content and total solids content were determined as shown below.
*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.
Yadanabon University Research Journal 2016, Vol.7, No.1

2.3.1 Determination of Acidity

Prepared vinegar (10 ml) was placed in a 250 ml of clean, dry conical flask. Then,
it was titrated with 0.1 N, standard sodium hydroxide solution by using phenolphthalein
indicator. The titrated volume was noted as soon as it turned into light purple (end point),
and the acidity of sample was determined as follows.

( )

Titre = Titrant value of 0.1 N, NaOH

Factor = 0.006005 (for acetic acid)
The results obtained are shown in Tables (2.1) to (2.5).

2.3.2 Determination of pH
The pH of prepared vinegar was determined by using digital pH meter (Pen Type
pH meter 009 (I), Range: 0.0-14.0). The glass electrode was first standardized by using
buffer solution of pH 7 and the electrode was adjusted to that value. Then, the pH value
of vinegar was measured and, the results obtained are shown in Table (2.1) to (2.5).

2.3.3 Determination of Alcohol Content

The alcohol content of prepared vinegar was determined by an alcoholmeter at
room temperature. The results obtained are shown in Tables (2.1) to (2.5).

2.3.4 Determination of Total Solids Content

Prepared vinegar (10 ml) was placed in a previously weighed, clean, dry stainless
steel dish and heated to dryness. Then, it was placed in an oven at 105ºC for 3 hours.
After that, it was cooled in a desiccator for 15 minutes and weighed again. This
procedure was repeated until a constant weight was obtained. The percentage of total
solids content of vinegar was calculated as follows.

( )

*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.
Yadanabon University Research Journal 2016, Vol.7, No.1

The results obtained are shown in Tables (2.1) to (2.5).

3. RESULTS AND DISCUSSION

Food waste in industrialized countries can be reduced by raising awareness among

food industries, retailers and consumers. There is a need to find good and beneficial use
for safe food that is presently thrown away. Recycling of fruit and vegetable wastes is
one of the most important means of utilizing it in a number of innovative ways yielding
new products and essential products required in human. A number of beverages such as
cider, beer, brandy, and vinegar could also be obtained from the fermentation of fruit
wastes. This research is to find out the possibility of using pineapple peelings for the
preparation of vinegar by two-stage fermentation process.

In this work, preparation of vinegar was carried out by varying the amount of
sugar (i.e., 10, 20, 30, 40, 50 and 60 g), the amount of yeast (i.e., 2, 2.5, 3, 3.5, 4 and 4.5
g), the amount of yeast nutrient (ammonium phosphate) (i.e., 3, 4, 5, 6 and 7 g) and
fermentation period (i.e., 2, 4, 6, 8, 10 and 12 weeks) while keeping the amount of
pineapple peel (180g) and distilled water (800 ml).

The effect of sugar contents on acidity of pineapple peel vinegar is shown in Table
(2.1). According to the results of Table (2.1), it was clearly seen that the vinegar prepared
by using 50 g of sugar has the highest acidity compared to the other prepared vinegar.
When the amount of sugar was lower than 50 g, the acidity was decreased because of the
insufficient amount of sugar for fermentation. The value of acidity was also decreased
when the amount of sugar was higher than 50 g. This may be probably due to the excess
amount of sugar that may inhibit the growth of yeast for fermentation.

Table (2.2) showed the effect of yeast contents on acidity in the preparation of
pineapple peel vinegar. It was observed that, the maximum acidity of vinegar was
obtained by using 3 g of yeast. The acidity of prepared vinegar found to be decreased
when the amount of yeast was higher than 3 g. When the amount of yeast was lower than

*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.
Yadanabon University Research Journal 2016, Vol.7, No.1

3 g, the acidity was also decreased because of the insufficient amount of yeast for
fermentation.

The effect of yeast nutrient (ammonium phosphate) contents on acidity of

prepared vinegar is shown in Table (2.3). The results from Table (2.3) show that the
highest acidity was obtained by using 5 g of yeast nutrient. If the amount of ammonium
phosphate was lower than 5 g, the acidity was decreased. When the amount of
ammonium phosphate was more than 5 g, the acidity was also decreased. This may be
due to the insufficient or the excess amount of ammonium phosphate that inhibits the
growth of yeast.

According to Table (2.4), it was apparent that the highest acidity was obtained at
fermentation periods of eight weeks. It can be seen that, the acidity was decreased when
the fermentation period was longer than eight weeks. That may be caused by the further
oxidation of acetic acid.

The characteristics of prepared vinegar, viz., acidity, pH, alcohol content and total
solids content were determined and the results are shown in Table (2.1) to (2.5). From
these results, it can be concluded that the characteristics of prepared vinegar are
comparable with literature values.

*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.
Yadanabon University Research Journal 2016, Vol.7, No.1

Table (2.1) Effect of Sugar Content on Acidity in the Preparation of Pineapple Peel
Vinegar

Weight of pineapple peel = 180 g Volume of distilled water = 800 ml

Weight of yeast = 2.5 g Weight of yeast nutrient = 4 g
No. Weight of Fermentation Acidity pH Alcohol Total Solids
Sugar (g) period (week) (w/v%) (v/v%) Content (w/w%)

1 10 6 3.8071 3.3 Nil 1

2 20 6 4.2535 3.2 Nil 1
3 30 6 4.4317 3 Nil 1
4 40 6 4.4636 3.1 Nil 2
5 50* 6 4.6118 2.9 Nil 1
6 60 6 4.3837 3 Nil 2

*Optimum condition

Table (2.2) Effect of Yeast Content on Acidity in the Preparation of Pineapple Peel
Vinegar

Weight of pineapple peel = 180 g Volume of distilled water = 800 ml

Weight of yeast = 2.5 g Weight of yeast nutrient = 4 g
No. Weight of Fermentation Acidity pH Alcohol Total Solids
Yeast (g) Period (week) (w/v%) (v/v%) Content (w/w%)

1 2 6 4.2687 3.1 Nil 1

2 2.5 6 4.5480 3.0 Nil 2
3 3* 6 5.1283 2.8 Nil 1
4 3.5 6 4.8085 2.9 Nil 1
5 4 6 4.3683 3.0 Nil 2
6 4.5 6 3.9513 3.2 Nil 2

*Optimum condition

*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.
Yadanabon University Research Journal 2016, Vol.7, No.1

Table (2.3) Effect of Yeast Nutrient (Ammonium Phosphate) Content on Acidity in the
Preparation of Pineapple Peel Vinegar

Weight of pineapple peel = 180 g Volume of distilled water = 800 ml

Weight of yeast = 2.5 g Weight of yeast nutrient = 4 g
No. Weight of Fermentation Acidity pH Alcohol Total Solids
Yeast Period (w/v%) (v/v%) Content (w/w%)
Nutrient (g) (week)
1 3 6 4.0996 3.2 Nil 0
2 4 6 4.4256 3.1 Nil 2
3 5* 6 5.0562 2.8 Nil 1
4 6 6 4.3878 3 Nil 1
5 7 6 4.1555 3.2 Nil 2

*Optimum condition

Table (2.4) Effect of Fermentation Period on Acidity in the Preparation of Pineapple

Peel Vinegar

Weight of pineapple peel = 180 g Volume of distilled water = 800 ml

Weight of sugar = 50 g Weight of yeast = 2.5 g
Weight of yeast nutrient =4 g
No. Fermentation Acidity pH Alcohol Total Solids
Period (week) (w/v%) (v/v%) Content (w/w%)
1 2 1.7669 3.6 6 2
2 4 3.5469 3.1 1 1
3 6 4.7851 2.8 Nil 1
4 8* 5.1636 2.5 Nil 1
5 10 4.4317 3.1 Nil 1
6 12 4.3396 3.1 Nil 1

*Optimum condition

*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.
Yadanabon University Research Journal 2016, Vol.7, No.1

Table (2.5) Comparison of the Characteristics of the Prepared Vinegar and Literature
Values

No. Characteristics of Prepared Pineapple Peel Literature

Vinegar Vinegar Value
1 Acidity (w/v%) 5.1636 4-8%*
2 pH 2.5 2.4-3.4*
3 Alcohol Content (v/v%) Nil Nil*
4 Total Solids Content 1 -
(w/w%)

*http://en.wikipedia.org/wiki/vinegar

4.CONCLUSION
The results of this research work have revealed that pineapple peels can be
developed into vinegar through simple fermentation, and vinegar making is a highly
profitable venture. The prepared vinegar from this work is suitable to be used in cooking
and in the preparation of pickles, sauces and marinades. This study also revealed that
while cleaning the environment by reducing discharge of food wastes into the
environment, an added value could be achieved through the conversion of food wastes
into useful products.

ACKNOWLEDGEMENTS
The authors would like to express profound gratitude to Rector Dr. Aye Kyaw,
and Pro-rectors Dr. Khin Ma Ma Tin and Dr. MyinzuMinn,Yadanabon University, for
giving a chance to submit this article. Deepest gratitude and profound thanks are
extended to Dr. DawYin Shwe, Professor and Head of Department of Industrial
Chemistry (Rtd.), Dagon University, for her permission to perform this research work
and providing research facilities at the department.

*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.
Yadanabon University Research Journal 2016, Vol.7, No.1

REFERENCES

1. Tan, S.C., 2005. “Vinegar Fermentation”, Department of Food Science, Louisiana

State University, Agricultural and Mechanical College.
2. Sandar Aye, 2014. “Study on the Preparation of Vinegar from Fruit Wastes
(Pineapple Peel and Apple Scrap)”, Dagon University.

3. SweSweAung, 2013. “Studies on the Preparation of Wine from Fruit Wastes

(Pineapple Peel)”, Dagon University.

4. FAO, 1998. “Fermented Fruits and Vegetables: A Global Perspective”.

5. Raji, Y.O. et al., 2012. “Production of Vinegar from Pineapple Peel”, Internationa
Journal of Advanced Scientific Research and Technology, Vol. 3.
6. Oguntoyinbo, S.I et al., 2011. “Chemical Properties of Vinegar Produced from Sweet
Orange Peels (Citrus Sinensis)”, Journal of Agriculture and Veterinary Sciences, Vol. 3.
7. Ángel González Benito Tarragona, 2005.“Application of Molecular Techniques for
Identification and Enumeration of Acetic Acid Bacteria”.

*
Professor and Head, Department of Industrial Chemistry, Yadanabon University.
**
Professor, Department of Industrial Chemistry, Mandalay University.