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Article
Examination of pH, Titratable Acidity and Antioxidant Activity in Fermented Milk
Author(s)
Julijana Tomovska*, Nikola Gjorgievski and Borche Makarijoski
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DOI:10.17265/2161-6213/2016.11-12.006
Affiliation(s)
Faculty of Biotechnical Sciences – Bitola University, “St. KlimentOhridski’’ - Bitola, Bitola 7000, R. Macedonia
ABSTRACT
As a fermentation medium homogenized and sterilized whole milk is used. The length of the fermentation was 4 hours, symbiosis of Streptococcus thermophilus and Lactobacillus delbruesciissp. Bulgaricus were used, to achieve the isoelectric point of casein 4.6 pH. Monitored parameters were: pH, titratable acidity and antioxidant activity (AOA) in a period of 15 days. It has been determined a decrease of pH value from 6.67 to 4.19, an increase of titratable acidity from 8.0 to 36.07 oSH and an enhancement of AOA from 6.13 to 47.4%.The determination of AOA was accordeda method which is used for different types of food, by using stable 2,2-diphenyl-1-pikrilhidrazil (DPPH) free radical and the absorbance was measured at 517nm on a spectrophotometer Spectroquant Pharo 300, Merck. The neutralization activity of the free radical was expressed as a percentage of inhibition of absorbance of DPPH. Milk fermented with Lactobacillus delbrueckii ssp. Bulgaricus, the highest level of AOA registered immediately after the process of fermentation with a value of 52.44%. The lowest value of AOA for the same symbiosis of cultures was observed at the third day after fermentation process kept at a temperature of 4 °C, with a value of 39.43%.
KEYWORDS
Yogurt, fermented products, pH, titratable acidity, antioxidant activity.
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