Acid whey is a by-product generated in large quantities during dairy processing, and is characterized by its low pH and high chemical oxygen demand. Due to a lack of reliable disposal pathways, acid whey currently presents a major sustainability challenge to the dairy industry. The study presented in this paper proposes a solution to this issue by transforming yogurt acid whey (YAW) into potentially palatable and marketable beverages through yeast fermentation. In this study, five prototypes were developed and fermented by Kluyveromyces marxianus, Brettanomyces bruxellensis, Brettanomyces claussenii, Saccharomyces cerevisiae (strain: Hornindal kveik), and IOC Be Fruits (IOCBF) S. cerevisiae, respectively. Their fermentation profiles were characterized by changes in density, pH, cell count, and concentrations of ethanol and organic acids. The prototypes were also evaluated on 26 sensory attributes, which were generated through a training session with 14 participants. While S. cerevisiae (IOCBF) underwent the fastest fermentation (8 days) and B. claussenii the slowest (21 days), K. marxianus and S. cerevisiae (Hornindal kveik) showed similar fermentation rates, finishing on day 20. The change in pH of the fermentate was similar for all five strains (from around 4.45 to between 4.25 and 4.31). Cell counts remained stable throughout the fermentation for all five strains (at around 6 log colony-forming units (CFU)/mL) except in the case of S. cerevisiae (Hornindal kveik), which ultimately decreased by 1.63 log CFU/mL. B. bruxellensis was the only strain unable to utilize all of the sugars in the substrate, with residual galactose remaining after fermentation. While both S. cerevisiae (IOCBF)- and B. claussenii-fermented samples were characterized by a fruity apple aroma, the former also had an aroma characteristic of lactic acid, dairy products, bakeries and yeast. A chemical odor characteristic of petroleum, gasoline or solvents, was perceived in samples fermented by B. bruxellensis and K. marxianus. An aroma of poorly aged or rancid cheese or milk also resulted from B. bruxellensis fermentation. In terms of appearance and mouthfeel, the S. cerevisiae (IOCBF)-fermented sample was rated the cloudiest, with the heaviest body. This study provides a toolkit for product development in a potential dairy-based category of fermented alcoholic beverages, which can increase revenue for the dairy industry by upcycling the common waste product YAW.

Dairy manufacturing generates whey by-products, many of them considered waste; others, such as whey permeate, a powder high in lactose and minerals from deproteinated whey, have unrealized potential. This study identified yeast species capable of utilizing lactose from whey permeate to produce ethanol or organic acids, and identified fungal species that reduced the acidity of whey by-products. Reconstituted whey permeate was fermented anaerobically or aerobically for 34 days, using species from Cornell University’s Food Safety Lab, Alcaine Research Group, and Omega Labs. Yeast species: Kluyveromyces marxianus, Kluyveromyces lactis, Dekkera anomala, Brettanomyces claussenii, Brettanomyces bruxellensis; mold species: Mucor genevensis and Aureobasidium pullulans. Density, pH, cell concentrations, organic acids, ethanol, and sugar profiles were monitored. Under anoxic conditions, K. marxianus exhibited the greatest lactose utilization and ethanol production (day 20: lactose non-detectable; 4.52% ± 0.02 ethanol). Under oxic conditions, D. anomala produced the most acetic acid (day 34: 9.18 ± 3.38 g/L), and A. pullulans utilized the most lactic acid, increasing the fermentate’s pH (day 34: 0.26 ± 0.21 g/L, pH: 7.91 ± 0.51). This study demonstrates that fermentation of whey could produce value-added alcoholic or organic acid beverages, or increase the pH of acidic by-products, yielding new products and increasing sustainability.

Acid whey from Greek-style yogurt (YAW) is an underutilized byproduct and a challenge for the dairy industry. One alternative is the fermentation of YAW by yeasts such as Saccharomyces, Brettanomyces, and Kluyveromyces spp., to produce new styles of fermented beverages. Previous research in our group suggested that the sugar profiles of the dairy coproducts impacted the fermentation profiles produced by B. claussenii. The present work aims to describe the fermentation of dairy sugars by S. cerevisiae, K. marxianus, and B. claussenii, under conditions comparable to those of YAW. For this purpose, four preparations of yeast nitrogen base, each containing 40 g/L of either lactose (LAC), glucose (GLU), galactose (GAL), or a 1:1 mixture of glucose and galactose (GLU:GAL), all at pH 4.20, were used as fermentation media. The fermentation was performed independently by each organism at 25 °C under anoxic conditions, while density, pH, cell count, ethanol, and organic acids were monitored. Non-linear modeling was used to characterize density curves, and Analysis of Variance and Tukey’s Honest Significant Difference tests were used to compare fermentation products. K. marxianus and S. cerevisiae displayed rapid sugar consumption with consistent ethanol yields in all media, as opposed to B. claussenii, which showed more variable results. The latter organism exhibited what appears to be a selective glucose fermentation in GLU:GAL, which will be explored in the future. These results provide a deeper understanding of dairy sugar utilization by relevant yeasts, allowing for future work to optimize fermentations to improve value-added beverage and ingredient production from YAW.

Under specific conditions of oxygen availability and lactose hydrolysis, Brettanomyces claussenii OYL-201 can convert glucose in dairy coproducts into ethanol, leaving the galactose almost untouched. This approach could be applied specifically to whey permeate (WP) to develop foods with low-glycemic loads and other potential health benefits. The aims of this research are to optimize the fermentation of WP by B. claussenii, to maximize the production of ethanol and galactose, and to characterize various products obtained with this approach. For this purpose, five fermentation factors were studied to determine their impacts on ethanol and galactose: temperature (20–40 °C), substrate concentration (5–15%TS), lactase enzyme/substrate ratio (0–40 IU/ g lactose), inoculation level (6–8 log cfu/mL), and time (6–30 days). Linear models, containing quadratic and interaction effects, were built for the optimization of both responses. Optimal levels were predicted for the maximum outputs of ethanol and galactose simultaneously, which utilized the following parameters: 15%TS, 37 IU / g lactose, 28 °C, 7.5 log cfu/mL, and 30 days, which together were predicted to produce 4.0%v/v ethanol and 51 g/L galactose in the final product. These parameters were applied to 18-L fermentations, and the fermentates were processed via distillation and freeze-drying. As a result, four product streams were obtained: a fermented product with 3.4%v/v ethanol and 56 g/L galactose, a 45%v/v ethanol distillate, a galactose-rich drink base (63 g/L), and a galactose-rich powder (55%w/w). These results demonstrate that it is possible to maximize the production of ethanol and galactose from WP and to develop novel, potentially functional bioproducts from this stream.

As the Greek-style yogurt market continues to experience prosperous growth, finding the most appropriate destination for yogurt acid whey (YAW) is still a challenge for Greek yogurt manufacturers. This study provides a direct alternative treatment of YAW by leveraging the abilities of Mucor circinelloides and Mucor genevensis to raise the pH of YAW and to produce fungal biomass with a high lipid content. Aerobic cultivations of these species were conducted in YAW, both with and without the addition of lactase, at 30 °C, and 200 rpm agitation. The density, pH, biochemical oxygen demand (BOD), biomass production, lipid content, fatty acid profile, and sugar and lactic acid concentrations were regularly measured throughout the 14-day cultivations. The data showed that M. genevensis was superior at deacidifying YAW to a pH above 6.0—the legal limit for disposing of cultured dairy waste. On the other hand, M. circinelloides generated more fungal biomass, containing up to 30% w/w of lipid with high proportions of oleic acid and γ-linolenic acid. Additionally, the treatments with lactase addition showed a significant decrease in the BOD. In conclusion, our results present a viable treatment to increase the pH of YAW and decrease its BOD, meanwhile generating fungal oils that can be further transformed into biodiesel or processed into functional foods or dietary supplements.

Shelf-stable milk is consumed worldwide, and this market is expected to continue growing. One quality challenge for UHT milk is age gelation during shelf life, which is in part caused by bacterial heat-stable proteases (HSP) synthesized during the raw milk storage period before heat processing. Some Pseudomonas spp. are HSP producers, and their ability to grow well at refrigeration temperature make them important spoilage organisms for UHT processors to control. Previous studies have shown that lactose oxidase (LO), a natural and commercially available enzyme that produces hydrogen peroxide and lactobionic acid from lactose, can control bacterial growth in raw milk. In this research, we investigated the ability of LO to control HSP producer outgrowth, and thus delay age gelation in UHT milk. Six strains of Pseudomonas spp. were selected based on their ability to synthesize HSP and used as a cocktail to inoculate both raw and sterile (UHT) milk at a level of 1 x 10(5) cfu/mL. Groups were treated with and without LO, stored for 4 d at 6 degrees C, and monitored for cell count and pH. Additionally, a sample from each was tested for HSP activity via particle size analysis (average effective diameter at 90 degrees angle and 658 nm wavelength) and visual inspection on each day of the storage period. The HSP activity results were contrasted using Tukey's HSD test, which showed that in UHT milk, a LO treatment (0.12 g/L) effectively prevented gelation as compared with the control. In raw milk, however, a concentration of 0.24 g/L of LO was needed to obtain a similar effect. This test was scaled up to 19-L pilot plant batches of raw milk where they were challenged with Pseudomonas cocktail, treated with LO for 3 d, and then UHT processed. Resulting UHT milk bottles were monitored for gelation. Significant differences in particle size between the LO-treated samples and the control were observed as early as 1 mo after processing, and gelation was not detected in the LO-treated samples through 6 mo of storage. These results demonstrated that LO can be used to delay age gelation in UHT milk induced by HSP-producing Pseudomonas spp., representing an opportunity to improve quality and reduce postproduction losses in the shelf-stable milk market sector.