DAIRY APPLICATIONS OF LACTIC ACID-PRODUCING YEASTS: MILK FERMENTATION CHARACTERIZATION AND DEVELOPMENT OF A GOUDA-STYLE CHEESE
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The dairy industry is one of the major food industries worldwide. Dairy products have been part of the human diet since ancient times, making cultured dairy products one of the most relevant food categories. Their popularity is related to their characteristic sensory profile, as well as their cultural relevance and health benefits. Therefore, their demand is high. The most important functional and sensory characteristics in cultured dairy products are attributed to the fermentation with lactic acid bacteria (LAB). However, these microorganisms are susceptible to bacteriophage, viruses capable of killing bacteria. Therefore, contamination with these viruses leads to defects, delays, or total loss of the involved products. Yeasts are not susceptible to these viruses and some strains can produce the main metabolite needed in dairy fermentations, lactic acid. Their applications in dairy are common but limited to combined fermentation with lactic acid bacteria. Thus, this study aimed to investigate the application of lactic acid-producing yeasts as the main acidifiers in dairy products, to provide an alternative to manufacturing cultured dairy products without LAB utilization. Results showed an efficient acidification of milk by the strains evaluated. The most promising strain showed a final pH of 3.31 ± 0.03 and an acidification rate of -0.35 ± 0.08 pH units/h while yielding an ethanol concentration of 0.72 ± 0.05 % v/v in lactase-treated UHT milk without any glucose supplementation at 30°C. For this reason, this strain was chosen to develop a Gouda-style cheese at a pilot plant level. The cheese was successfully executed in the Cornell Dairy Pilot plant in 195 kg batches. Evaluations of its physicochemical, rheological, and sensory characteristics showed differences from a Gouda cheese manufactured with the traditional starter cultures. However, an overall liking score of 6.32 vs 6.59 for the control, and a purchase intent of 49% by 90 participants showed the potential of this cheese to be a successful product in the market. This project aims to lay the groundwork for further product development of dairy products using lactic acid-producing yeasts.