Value addition to acid whey from greek yogurt processing with millets (kodo and proso) for development of nutritious food products
Authors:   , Malik Sargun 
Published: February 2023

[EMBARGOED UNTIL 12/1/2023] The disconnect between massive demand and abundant supply of food has resulted in millions of people suffering from hunger and billion metric tons of food being wasted. Circular food economy could be a solution to the problem, whereby there is the production of healthy food products using the byproduct and waste streams. Hence, the objective of this project was to increase this statistic, specifically targeting the Greek yogurt industry which produces 2.31 million metric tons of acid whey every year. Acid whey is produced when the manufactured yogurt is strained for obtaining a thicker texture which is a key attribute of Greek yogurt. This acid whey is currently being mismanaged and being thrown into the environment causing land and water pollution. Thus, there is a need to develop new environmentally friendly methods for the upcycling of acid whey. Based on the physicochemical characteristics and composition analysis, acid whey has huge potential in health industry. Likewise, there are underutilized ancient grains, millets that are highly nutritive with several health benefitting properties. These millets are rich in protein, carbohydrates, vitamins, and minerals. They help in preventing cardiovascular disorders, controlling blood sugar levels, blood pressure etc. Due to a lack of awareness and requisite processing technologies, these millets are not being used to full capacity. The project aimed to bridge the gap between food waste and food supply by combining acid whey and millets for formation of a matrix that has both probiotic and prebiotic properties. One of the major drawbacks with acid whey that limits its usage in commercial set up is its high lactic acid content and consequent low pH. Millets being of alkaline nature help in increasing the pH of matrix and enabling efficient processing. The research methodology for the project included chemical composition and functional analysis of acid whey and millet matrix. The chemical composition was conducted for analysis of the macro and micronutrients present in the sample matrix. The functional characterization was conducted for analysis of antioxidant properties and antinutritional factors. The acid whey-millet feed was processed using the spray drying process to obtain a shelf-stable product encapsulating all the bioactive compounds present in the acid whey. The operating parameters were optimized based on the analysis of the physical properties of the powder. The physical characterization was based on the density (Bulk, tapped), flow character and reconstitution properties (dispersibility, water holding capacity and water solubility) of the powder. The resultant powder was also confirmed for its chemical and microbiological properties to evaluate that to what extend the powder was able to retain those properties and if there was any enhancement or degradation. The matrix was also analyzed for its encapsulation potential for folic acid (Vitamin B9) In terms of chemical properties, increase in antioxidant properties and decrease in antinutritional factors was observed for both raw matrix and spray dried matrix. Adding millets to acid whey led to a high yield percentage of 89 to 94 percent of powder. Water activity (aw were found to be between 0.24 to 0.28), similar to the values obtained for commercial food powders. According to the calculated Carr Index and Hausner ratio values, the obtained powder was of free-flowing character. High water solubility and dispersibility was observed for the reconstituted acid whey millet powder and acid whey-millet-vitamin powder. When analyzed for nutritional composition enhancement in protein content, minerals and polyphenolic content was observed. However, the encapsulation efficiency for folic acid was around 11 percent within the acid whey-millet matrix but it was able to encapsulate the more than the daily required value of folic acid for adult males and females i.e., 400 µg DFE when compared with commercial supplements. Overall, the study provided with an alternative method of utilization of acid whey and millets that has humongous potential to be used in commercial set up in food and nutraceutical industry.