Strategies to extend the shelf life of sheep and goat cheese whey under refrigeration: Nisin, bioprotective culture, and acidification

Abstract

The valorization of sheep and goat cheese whey are important from economic, social and environmental perspectives. However, their low microbiological and physical stabilities are major challenges, especially for artisanal productions. In this study, the effectiveness of nisin addition, bioprotective culture (Lacticaseibacillus casei) inoculation and direct acidification (pH 2.5–4.5) was evaluated to improve the stability of pasteurized (75 °C/5 min) sheep and goat cheese whey. All strategies were effective in controlling the native microbial population, with minimal or no change in the pH or acidity during 28 days/7 °C, whereas samples only pasteurized reached counts of up to 8 log CFU/mL. Phase separation occurred in all samples, but at different rates and intensities. Acidification at pH 3.5 and 4.5 resulted in higher creaming rates (up to 30%), even without change in fat globule size, and sedimentation (up to 6%), due to protein particle agglomeration - that increased D[3,2] values by up to 27% and reduced the specific surface area by around 20%. Conversely, acidification at pH 2.5 or the addition of nisin or L. casei resulted in samples with smaller particle size and better stability to creaming and sedimentation. The results indicated that nisin addition or L. casei inoculation are possible strategies to improve the shelf life of sheep and goat pasteurized whey, which can be used even by artisanal producers, and thus contributing for their valorization.