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

BOCKOR, S.; GUAITA, S.; CORFIELD, R.; ROSET, V.; GORDILLO, T.; RUZAL S.; PALOMINO, M.; ALLIEVI, M.

Buenos Aires

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

Asociación Argentina de Tecnólogos Alimentarios - AATA

Probiotic dairy products are highly desirable functional foods due to their health benefits, but their efficacy depends on the viability of probiotics throughout the product´s shelf life and in the gastrointestinal tract. Blackcurrant (BC) and its derivatives are known for their outstanding antioxidant capacity and multiple health benefits, as well as their antimicrobial properties against pathogenic microorganisms, making them an ideal ingredient in dairy products. However, the effects of BC and its interaction with starters and probiotics during the manufacturing process, especially in yogurts, remain largely unexplored. In previous works using the mini-yogurt system, we showed that BC 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 starters cultures in yogurt 1% and 2.5% BC formulations. While the concentration of BC did not affect the growth of Lactobacillus bulgaricus, it did decrease the growth of Streptococcus thermophilus proportionally to the BC content. Using lactate, we recreated the acidity generated by BC and found that pH was not the only cause of growth inhibition for Streptococcus thermophilus, but there is another biomolecule in BC that generates an antimicrobial effect. However, the CFU values obtained were sufficient for the requirements of yogurt and reduced the product´s elaboration time by almost half. The second objective was to characterize the chosen 1% BC formulation with Lentilactobacillus kefiri (Len. kefiri). We seek to obtain information on the physicochemical characteristics pre and post-fermentation of yogurt containing blackcurrant. For this, viable cell count on differential media, pH, syneresis, color and antioxidant activity were evaluated. The incorporation of BC did not inhibit the probiotic Len. kefiri, which maintained viability during the fermentation process and during the shelf life of the product, reaching log CFU/ml values of 7.71±0.05 after 21 days. As a desirable characteristic, the presence of BC reduced the syneresis percentage of the yogurt from (77.7±0,9)% to (70.1±0.5)%. A measurement of the CIELAB color space was conducted, and the recorded values exhibited slight modifications during refrigeration, with a ΔE* value considered normal. The antioxidant capacity of the formulation 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 the presence of BC. The findings suggest that acidity is not the only factor affecting fermentation, 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 time was reduced. It is noteworthy that despite the potential inhibitory effects of polyphenols on probiotic bacteria, BC did not adversely affect the survival of Len. kefiri. Therefore, a probiotic yogurt with antioxidant capacity and acceptable parameters over time was obtained.