A yogurt containing blackcurrant and Lentilactobacillus kefiri: from fermentation kinetics to functional characterization.

BOCKOR, SABRINA S.; GUAITA, SOL; CORFIELD, ROCIO; ROSET, VIOLETA; GORDILLO, TANIA B.; RUZAL, SANDRA M.; PALOMINO, M. MERCEDES; ALLIEVI, MARIANA C.

Ciudad Autónoma de Buenos Aires

Congreso; XVIII Congreso Argentino de Ciencia y Tecnología de Alimentos; 2023

ABSTRACTProbiotic dairy products are highly desirable functional foods due to their healthbenefits, but their efficacy depends on the viability of probiotics throughout theproduct's shelf life and in the gastrointestinal tract. Blackcurrant (BC) and its derivativesare known for their outstanding antioxidant capacity and multiple health benefits, aswell as their antimicrobial properties against pathogenic microorganisms, making theman ideal ingredient in dairy products. However, the effects of BC and its interaction withstarters and probiotics during the manufacturing process, especially in yogurts, remainlargely unexplored. In previous works using the mini-yogurt system, we showed thatBC would have an effect on the fermentation process, shortening the production time.The first objective of the current research is to study the fermentation kinetics of starterscultures in yogurt 1% and 2.5% BC formulations. While the concentration of BC did notaffect the growth of Lactobacillus bulgaricus, it did decrease the growth ofStreptococcus thermophilus proportionally to the BC content. Using lactate, werecreated the acidity generated by BC and found that pH was not the only cause ofgrowth inhibition for Streptococcus thermophilus, but there is another biomolecule inBC that generates an antimicrobial effect. However, the CFU values obtained weresufficient for the requirements of yogurt and reduced the product's elaboration time byalmost half. The second objective was to characterize the chosen 1% BC formulationwith Lentilactobacillus kefiri (Len. kefiri). We seek to obtain information on thephysicochemical characteristics pre and post-fermentation of yogurt containingblackcurrant. For this, viable cell count on differential media, pH, syneresis, color andantioxidant activity were evaluated. The incorporation of BC did not inhibit theprobiotic Len. kefiri, which maintained viability during the fermentation process andduring the shelf life of the product, reaching log CFU/ml values of 7.71±0.05 after 21days. As a desirable characteristic, the presence of BC reduced the syneresis percentageof the yogurt from (77.7±0,9)% to (70.1±0.5)%. A measurement of the CIELAB colorspace was conducted, and the recorded values exhibited slight modifications duringrefrigeration, with a ΔE* value considered normal. The antioxidant capacity of theformulation was measured using FRAP and ABTS•+ methods, giving values of(0.100±0.010) and (0.282±0.001) mg EAG/g of yogurt, respectively. This means a 28%increase in antioxidant activity compared to the active ingredient alone. In conclusion,this study provides valuable insights into the fermentation kinetics of yogurt in thepresence of BC. The findings suggest that acidity is not the only factor affectingfermentation, but there is also an inhibitory effect on one of the starter cultures.Additionally, a probiotic yogurt with 1% BC was formulated, and its production timewas reduced. It is noteworthy that despite the potential inhibitory effects of polyphenolson probiotic bacteria, BC did not adversely affect the survival of Len. kefiri. Therefore,a probiotic yogurt with antioxidant capacity and acceptable parameters over time wasobtained.