Organic acids profiles in lactose-hydrolyzed yogurt with different matrix composition

Abstract

International audienceThe composition of the dairy matrix used in yogurt manufacture could influence the metabolic activity of yogurt starter and the compounds produced during fermentation. In this way, the lactose hydrolysis with a β-galactosidase enzyme and the supplementation with dairy powders to obtain different types of delactosed yogurts for lactose-intolerant people modifies the milk base composition. In this work, we studied the influence of the addition of different doses of β-galactosidase and levels of dairy powders on organic acids profile during the manufacture and storage of two varieties of yogurt (natural and sweetened). Lactose, glucose, galactose, titratable acidity, fermentation time, and microbiological counts were also evaluated. The mean proportions of lactose/glucose/galactose in relation to the total sugars were 18:36:46 in hydrolyzed yogurts, while they were 81:4:15 in unhydrolyzed ones. In supplemented yogurts, the content of lactose, citric, orotic, and hippuric acids were significantly increased. The starter population was similar in all yogurts, but some changes in their activity were evidenced due to both factors studied. The fermentation time was slightly increased, and the lactic acid content and the titratable acidity were significantly increased due to fortification while they were decreased by enzyme addition. These results are probably due to the increase in the buffer properties of the milk base by the dairy powder addition and due to an inhibition of the starter activity caused by changes in the carbohydrate profile. The results demonstrated that the changes in the matrix composition of the yogurt affected the organic acids profile, above all the lactic acid content

Effect of reduction of lactose in yogurts by addition of β‐galactosidase enzyme on volatile compound profile and quality parameters

“…Recently, Vénica et al . () studied the carbohydrate profiles in drinkable and stirred yogurts made with and without added β‐galactosidase. They observed that starter cultures metabolise rapidly the glucose to growth as this sugar was not detected in unhydrolysed fresh yogurts, whereas in delactozed yogurts, there was an overproduction of glucose that lactic acid bacteria could not fully use.…”

“…Lactose and acid lactic content in yogurts was determined during fermentation and storage by HPLC method according to Vénica et al . (). Analyses were performed in duplicate.…”

“…Total lactic acid bacteria were enumerated according to the procedure described by Vénica et al . (). Results were expressed as Dornic degree (1°D = 100 mg lactic acid L −1 ).…”

“…Recently, Vénica et al . (, ) studied the influence of some variables to hydrolyse the lactose (three levels of β‐galactosidase and the time of its addition) and different matrix composition on carbohydrate and organic acids profiles during manufacture of drinkable and stirred yogurts. So far, according to our knowledge, no work has been performed to see the degree in which the bioformation of volatile compounds is affected by the change of sugar profile during manufacture of delactozed yogurts.…”

Influence of lactose hydrolysis on galacto‐oligosaccharides, lactose, volatile profile and physicochemical parameters of different yogurt varieties

“…Summarizing, the inclusion of β ‐galactosidase enzyme in yogurt making changes the carbohydrate pattern in the matrix; hence different relative proportions of lactose, glucose, galactose and GOS are found during the process. This different sugar profile could affect the metabolic activity of cultures and consequently the production of derived compounds as well as some physicochemical characteristics of the product . Besides, the extent of these changes can be influenced by the matrix composition.…”