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Analysis of the Physicochemical Properties and Determination of Acetic Acid Content of Banana Vinegar
by Bartolome V. Casuga Jr.
College of Home Economics, University of the Philippines, Diliman, Quezon City
Abstract: In this study, the physicochemical properties (pH, TSS, and color) and acetic acid content of banana vinegar were analyzed. Cavendish banana (Musa Acuminata Colla var. Cavendish) was pasteurized and the TSS was adjusted using sugar, after which it went through alcoholic and acetic acid fermentation. Then, the vinegar was subjected to different analyses. After 11 days of fermentation, the vinegar has found out to have a pH of 3.28, TSS of 4.2, a color of pale yellow brown and contains 3.66 (w/v) % acetic acid. The resulting product doesn’t conform to the set standards.
Introduction
The word vinegar is derived from the French words vin aigre, meaning sour wine. Vinegar is classified as acetic acid fermentation (Adams, 1980; Steinkraus, 2002). It is produced via two-stage fermentation. The first stage is the anaerobic conversion of sugars into ethyl alcohol by the action of yeasts followed by the oxidation of the alcohol to acetic acid by Acetobacter bacteria (Pederson, 1967). It is now one of the most widely used ingredients in the food industry, with worldwide production of 1 million L per year (Hutkins, 2006) and the per capita consumption is 2 liters (Wood, 1985). In the past it has served a wide variety of functions, but today its use is largely confined to food flavoring, production and preservation (Adams, 1980.
Pederson (1967) said that vinegar can be prepared from any watery substance that contains sugar. Since banana is a high in sugar and carbohydrate-containing fruit, it has a high potential for alcohol production (Camarungan, 1940) and subsequently fermented into vinegar. Adams (1980) cited banana vinegar production as a small-scale industry especially in developing countries like the Philippines. There are already studies of banana vinegar from different varieties and some are made from banana peel. According to Co Seteng (1983), banana peel can be used for vinegar production, but Adams (1980) said that it can be a source of contamination of some fungi and microorganisms even though it can add to the total fermentable sugar of the fruit. The process is simple, the capital requirement is limited, and banana wastes can be used for the production (Adams, 1980.
Banana is the premiere fruit crop in the Philippines today and sometimes compared to coconut as the “tree of life” (PCCARD, 1988). The banana fruit can be eaten fresh, processed or cooked. As food, it can be processed as puree, jam, jelly, chips, flour, catsup, wine and vinegar (PCCARD, 1988). From 2005, the Philippines is producing more than 6 million metric tons of bananas a year (BSA, 2007) putting Philippines to top 5 producing country to the whole world. Out of 80 cultivars of banana, Cavendish is produced specifically for export market (PCCARD, 1988). The Cavendish is a greenish-yellow fruit when ripe under normal temperature. The pulp is white to cream, fine-textured, and sweet. It is rich in vitamins and minerals (PCCARD, 1988). It is the second biggest cultivar produced next to Saba (PCCARD, 1988). It comprises almost 26% of total banana production. Based on the parameters set by the Bureau of Agricultural Statistics (2008), 6% of the banana produce is turned into feed and waste. Therefore, approximately 93,000 metric tons of Cavendish goes into feed and waste.
The Administrative Order No. 1345 of 1970 by the Department of Health under the Office of the Secretary here in the Philippines identified some important standards for vinegar. It shall have acidity not less than 4% (w/v), should have at least 1.5% total soluble solids, and not less than 0.18% ash and many more. The Codex Alimentarius Commission of the Joint FAO/WHO Food Standards Programme defined vinegar to be fit for human consumption, produced from a suitable raw material and origin, containing starch, sugars or starch and sugars, by the process of double fermentation, alcoholic and acetous, and contains a specified amount of acetic acid. Thus, dilute glacial acetic acid and sometimes colored with caramel is found to be falsely described as vinegar in the market.
In this study, we want to analyze the physicochemical properties (pH, total soluble solids (TSS), and color) and to determine the acetic acid content of banana vinegar if it conforms with the set standards. Aside from that, it also involves the utilization of wasted Cavendish for small-scale and bigger scale enterprises and for future reference and use.
Materials and Method
Banana Vinegar Preparation
Let alone method was used to ferment banana vinegar.
One kilogram of Cavendish banana pulp was mashed and diluted with water (1:3). The mixture was extracted using cheesecloth to remove the solid parts. The extract was pasteurized at 60°C for 15 minutes. One cup of sugar was added for every 4 cups of the extract. After which, two tsp of yeast was added for every 2cups of the mixture. Using a fermentation set-up, the mixture went through alcoholic fermentation for 6 days. Then, it was transferred to a wide mouthed plastic jar and one cup of starter vinegar was added for every three cups of solution. The jar was covered with cheesecloth and let it fermented for 5 days. Lastly, the vinegar was pasteurized at 60°C for 15 minutes, cooled down, and transferred to bottles.
pH determination
The pH values of banana vinegar samples were measured at 20-250C using a pH meter (Cyberscan pH500, Eutech Cybernetics, Singapore) after calibrating with pH 4.0 and 7.0 standard buffers. Average of three trials was done.
TSS determination
The TSS values of the banana vinegar sample were measured using traditional handheld Refractometer (Atago Hand Refractometer) three trials was done.
Color determination
Banana vinegar samples were analyzed for three color indices, L* (white to black), a* (red to green), and b* (yellow to blue) using a Hunterlab colorimeter, model D25-9 (Hunterlab, Reston, VA). Triplicate readings of each index were made by rotating the sample 120 ° and taking the readings in each of the positions.
Acetic Acid Determination
The (w/v) % acetic acid content was determined using the standard method for determination of acetic acid by Nielsen (1994). A standardized 0.1N NaOH was used to determine the endpoint (pH 8.2) of a phenolphthalein indicator. An average of three trials was taken to 50mL banana vinegar samples.
Results and Discussion
The fermentation of the banana vinegar took 11 days, 6 days for alcohol fermentation and 5 days for acetic acid fermentation. The table below shows the results of the physicochemical tests done.
Table 1. pH, TSS, Acetic acid, & color values
pH 3.28 L* 12.21 ± 0.25
TSS 4.20 A* 2.25 ± 0.07
Acetc acid %(w/v) 3.66 B* 7.13 ± 0.22
Comparing to the results of banana vinegar from Adams (1980), pH is 3.12 and TSS is 1.74, the values above is much higher. The percent acidity doesn’t conform to the standards that banana vinegar must contain at least 4% (w/v). The color of the vinegar is somewhat near to pale yellow brown color. The L* value represents lightness where L* = 0 is completely black, and L* = 100 is completely white. The a* value represents red-green colors: positive a* values mean red colors and negative a* values mean green colors. The b* value represents yellow-blue colors: positive b* values mean yellow colors and negative b* values mean blue colors. According to Adams (1980), banana vinegar has amber color because it darkens through time.
Mashing of the banana and diluting it with water helps to release the soluble sugars from the fruit. Addition of sugar adds to the fermentable sugars to obtain the required alcohol content. It takes 7 to 10 days to convert all the fermentable sugars to alcohol (Hutkins, 2006) by the action of yeast (Saccharomyces cerevisaea) (Adams, 1980). Let alone method for vinegar fermentation takes a month or longer to reach its optimum physicochemical characteristics (Hutkins, 2006). Pasteurizing the vinegar for 15 minutes at 60°C kills targets the acetic acid bacteria, lactic acid bacteria, fungi and yeasts to stop further fermentation (Hutkins, 2006). Furthermore, pH below 4 limits bacteria but not to yeast and fungi. Theoretically, as alcohol content increases, TSS decreases during alcoholic fermentation. This is due to the conversion of sucrose to alcohol.
Figure 1.Theoretical conversion of sugar to alcohol.
C6H12O6 2 CO2 + 2 C2H5OH
Glucose/Fructose Carbon dioxide Ethanol
And during acetic acid fermentation, alcohol decreases as acidity increases. This is mainly because ethanol is oxidized by the acetic acid bacteria to acetic acid.
Figure 2. Theoretical oxidation of alcohol to acetic acid
C2H5OH + O2 CH3CO2H + H2O
Ethanol Oxygen acetic acid water
Conclusion
The physicochemical properties and the acetic acid content of the banana vinegar don’t conform to the set standards. The main reason is due to short period of fermentation. It is important to observe the period of fermentation because it is time dependent aside from the factors like temperature, starting materials, etc. (Wood, 1985). As a result, this study recommends that the vinegar must be subjected to sensory analysis, descriptive and consumer acceptance, for further evaluation. Moreover, this study encourages further development of this study by addition of some spices and food additives and by application of new principles discovered, aside from extending the fermentation time.
References
Pederson (1967) said that vinegar can be prepared from any watery substance that contains sugar. Since banana is a high in sugar and carbohydrate-containing fruit, it has a high potential for alcohol production (Camarungan, 1940) and subsequently fermented into vinegar. Adams (1980) cited banana vinegar production as a small-scale industry especially in developing countries like the Philippines. There are already studies of banana vinegar from different varieties and some are made from banana peel. According to Co Seteng (1983), banana peel can be used for vinegar production, but Adams (1980) said that it can be a source of contamination of some fungi and microorganisms even though it can add to the total fermentable sugar of the fruit. The process is simple, the capital requirement is limited, and banana wastes can be used for the production (Adams, 1980.
Banana is the premiere fruit crop in the Philippines today and sometimes compared to coconut as the “tree of life” (PCCARD, 1988). The banana fruit can be eaten fresh, processed or cooked. As food, it can be processed as puree, jam, jelly, chips, flour, catsup, wine and vinegar (PCCARD, 1988). From 2005, the Philippines is producing more than 6 million metric tons of bananas a year (BSA, 2007) putting Philippines to top 5 producing country to the whole world. Out of 80 cultivars of banana, Cavendish is produced specifically for export market (PCCARD, 1988). The Cavendish is a greenish-yellow fruit when ripe under normal temperature. The pulp is white to cream, fine-textured, and sweet. It is rich in vitamins and minerals (PCCARD, 1988). It is the second biggest cultivar produced next to Saba (PCCARD, 1988). It comprises almost 26% of total banana production. Based on the parameters set by the Bureau of Agricultural Statistics (2008), 6% of the banana produce is turned into feed and waste. Therefore, approximately 93,000 metric tons of Cavendish goes into feed and waste.
The Administrative Order No. 1345 of 1970 by the Department of Health under the Office of the Secretary here in the Philippines identified some important standards for vinegar. It shall have acidity not less than 4% (w/v), should have at least 1.5% total soluble solids, and not less than 0.18% ash and many more. The Codex Alimentarius Commission of the Joint FAO/WHO Food Standards Programme defined vinegar to be fit for human consumption, produced from a suitable raw material and origin, containing starch, sugars or starch and sugars, by the process of double fermentation, alcoholic and acetous, and contains a specified amount of acetic acid. Thus, dilute glacial acetic acid and sometimes colored with caramel is found to be falsely described as vinegar in the market.
In this study, we want to analyze the physicochemical properties (pH, total soluble solids (TSS), and color) and to determine the acetic acid content of banana vinegar if it conforms with the set standards. Aside from that, it also involves the utilization of wasted Cavendish for small-scale and bigger scale enterprises and for future reference and use.
Materials and Method
Banana Vinegar Preparation
Let alone method was used to ferment banana vinegar.
One kilogram of Cavendish banana pulp was mashed and diluted with water (1:3). The mixture was extracted using cheesecloth to remove the solid parts. The extract was pasteurized at 60°C for 15 minutes. One cup of sugar was added for every 4 cups of the extract. After which, two tsp of yeast was added for every 2cups of the mixture. Using a fermentation set-up, the mixture went through alcoholic fermentation for 6 days. Then, it was transferred to a wide mouthed plastic jar and one cup of starter vinegar was added for every three cups of solution. The jar was covered with cheesecloth and let it fermented for 5 days. Lastly, the vinegar was pasteurized at 60°C for 15 minutes, cooled down, and transferred to bottles.
pH determination
The pH values of banana vinegar samples were measured at 20-250C using a pH meter (Cyberscan pH500, Eutech Cybernetics, Singapore) after calibrating with pH 4.0 and 7.0 standard buffers. Average of three trials was done.
TSS determination
The TSS values of the banana vinegar sample were measured using traditional handheld Refractometer (Atago Hand Refractometer) three trials was done.
Color determination
Banana vinegar samples were analyzed for three color indices, L* (white to black), a* (red to green), and b* (yellow to blue) using a Hunterlab colorimeter, model D25-9 (Hunterlab, Reston, VA). Triplicate readings of each index were made by rotating the sample 120 ° and taking the readings in each of the positions.
Acetic Acid Determination
The (w/v) % acetic acid content was determined using the standard method for determination of acetic acid by Nielsen (1994). A standardized 0.1N NaOH was used to determine the endpoint (pH 8.2) of a phenolphthalein indicator. An average of three trials was taken to 50mL banana vinegar samples.
Results and Discussion
The fermentation of the banana vinegar took 11 days, 6 days for alcohol fermentation and 5 days for acetic acid fermentation. The table below shows the results of the physicochemical tests done.
Table 1. pH, TSS, Acetic acid, & color values
pH 3.28 L* 12.21 ± 0.25
TSS 4.20 A* 2.25 ± 0.07
Acetc acid %(w/v) 3.66 B* 7.13 ± 0.22
Comparing to the results of banana vinegar from Adams (1980), pH is 3.12 and TSS is 1.74, the values above is much higher. The percent acidity doesn’t conform to the standards that banana vinegar must contain at least 4% (w/v). The color of the vinegar is somewhat near to pale yellow brown color. The L* value represents lightness where L* = 0 is completely black, and L* = 100 is completely white. The a* value represents red-green colors: positive a* values mean red colors and negative a* values mean green colors. The b* value represents yellow-blue colors: positive b* values mean yellow colors and negative b* values mean blue colors. According to Adams (1980), banana vinegar has amber color because it darkens through time.
Mashing of the banana and diluting it with water helps to release the soluble sugars from the fruit. Addition of sugar adds to the fermentable sugars to obtain the required alcohol content. It takes 7 to 10 days to convert all the fermentable sugars to alcohol (Hutkins, 2006) by the action of yeast (Saccharomyces cerevisaea) (Adams, 1980). Let alone method for vinegar fermentation takes a month or longer to reach its optimum physicochemical characteristics (Hutkins, 2006). Pasteurizing the vinegar for 15 minutes at 60°C kills targets the acetic acid bacteria, lactic acid bacteria, fungi and yeasts to stop further fermentation (Hutkins, 2006). Furthermore, pH below 4 limits bacteria but not to yeast and fungi. Theoretically, as alcohol content increases, TSS decreases during alcoholic fermentation. This is due to the conversion of sucrose to alcohol.
Figure 1.Theoretical conversion of sugar to alcohol.
C6H12O6 2 CO2 + 2 C2H5OH
Glucose/Fructose Carbon dioxide Ethanol
And during acetic acid fermentation, alcohol decreases as acidity increases. This is mainly because ethanol is oxidized by the acetic acid bacteria to acetic acid.
Figure 2. Theoretical oxidation of alcohol to acetic acid
C2H5OH + O2 CH3CO2H + H2O
Ethanol Oxygen acetic acid water
Conclusion
The physicochemical properties and the acetic acid content of the banana vinegar don’t conform to the set standards. The main reason is due to short period of fermentation. It is important to observe the period of fermentation because it is time dependent aside from the factors like temperature, starting materials, etc. (Wood, 1985). As a result, this study recommends that the vinegar must be subjected to sensory analysis, descriptive and consumer acceptance, for further evaluation. Moreover, this study encourages further development of this study by addition of some spices and food additives and by application of new principles discovered, aside from extending the fermentation time.
Adams, M.R..1980. The small-scale production of vinegar from bananas.Tropical Product Institute, 56/62 Grays Inn Road, London
Association of Official Analytical Chemists.1975.Official Methods of Analysis of the Association of Official Analytical Chemists.12th edn.(ed. W. Horwitz).Washington D.C.: Association of Official Analytical Chemists
Bureau of Agricultural Statistics.(2008). Supply and Utilization Accounts, Philippines, 1990 – 2006
Camarungan, R.G..(1940).Biochemical changes in bananas during ripening.MS Thesis.College of Agriculture, University of the Philippines-Los Banos, Laguna
Co Seteng, Y.S..1983.Development of Vinegar from Saba Peels (Musa Sarpentum var. compresa).College of Home Economics, University of the Philippines, Diliman, Quezon City
http://biological-diversity.info/invasive_musa.htm. Retrieved on January 10,2007
Frazier, W.C. & D.C. Westhoff.(1988).Food Microbiology.4th ed. New York: McGraw-Hill Book, Co.
Hutkins, R.W..(2006).Microbiology and Technology of fermented Foods.Blackwell Publishing, USA
Pederson, C.S..1967.Processing by Fermentation.Connecticut: AVI Publishing Co.
Ploetz, R.C., et.al..2007, Banana and plantain—an overview with emphasis
on Pacific island cultivars.Species profile for Pacific Island Agroforestry from www.tradionaltree.org
PCCARD Technical Bulletin Series No.66.(1988).The Philippines recommends for banana
Pontiveros, C.R..(1952).Alcohol production from banana fruits.MS Thesis. College of Agriculture, University of the Philippines-Los Banos, Laguna
Quisimbing, E.A..(1919).Studies of Philippine bananas.Manila: Bureau of Printing
Stenkrauss, K.H..2002.Fermentations in the World Processing.Comprehesive Reviews on Food Science and Food Safety Journal
Wood, J.B..(1985).Microbiology of Fermented Foods.(vol.1).Elsevier Applied Science Publishers, London and NY
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