Master of Science / Food Science Institute / Jayendra Amamcharla / Greek yogurt is one of the largest-growing sectors in the dairy industry accounting for over 25% of yogurt sales in the United States. Greek yogurt is produced by removing a portion of water and water soluble components from yogurt. Consequently, a large quantity of Greek yogurt whey (GYW) is being produced as a co-product. GYW is compositionally different from cheese whey, and thus poses economic and environmental challenges to the dairy industry. The objective of the present study was to evaluate two physical treatments as alternative methods for separating valuable GYW components: magnetic fluid treatment (MFT) and the addition of sepiolite, a clay mineral. A MFT chamber was designed using four pairs of neodymium magnets arranged to produce a magnetic field strength of 0.6 Tesla. Three batches of GYW each from two manufacturers were procured. A 2×3 factorial design was used with MFT or without MFT and the addition of zero, two, or four grams of sepiolite per 100g of GYW. The pH of GYW was adjusted to 7.2 using 5N NaOH solution, and the GYW was pumped at a rate of 7.5 L/min through the MFT system with or without MFT chamber attached. The sample was split into three sub-samples, heated to 80°C, and sepiolite was added as per the experimental design. The samples were centrifuged at 1,000g for five minutes. The top aqueous layer was separated and analyzed for total solids, ash, lactose, protein, calcium, phosphates, and sodium content along with color. MFT did not influence the analyzed whey components (P > 0.05) except for lactose. However, addition of sepiolite influenced protein content and a* and b* color values for the top aqueous layers (P < 0.05). Both levels of sepiolite addition resulted in about a 50% decrease in protein compared to original GYW. Adding two grams of Sepiolite per 100g of GYW from manufacturer 1 resulted in b* decreasing from 25.99 to 8.16 compared to treated GYW with no sepiolite. Sepiolite was found to have possible applications in the removal of proteins and color pigments in GYW.

Acid whey, a byproduct of Greek yogurt production, has little commercial value due to its low protein content and is also environmentally harmful when disposed of as waste. However, as a product of microbial fermentation, acid whey could be a rich source of beneficial metabolites associated with fermented foods. This study increases understanding of acid whey composition by providing a complete metabolomic profile of acid whey. Commercial and lab-made Greek yogurts, prepared with three different bacterial culture combinations, were evaluated. Samples of unfermented yogurt mix and cultured whey from each batch were analyzed. Ultra-high-performance liquid chromatography/tandem mass spectrometry metabolomics were employed to separate and identify 477 metabolites, including many with potential health benefits similar to those provided by yogurt, such as creatine and acetylcarnitine. Examples of other metabolites identified in the acid whey include beneficial phospholipids (1,2-dilinoleoyl-sn-glycero-3-phosphocholine) and sphingolipids; compounds with neuroprotective (glycerophosphorylcholine) or cardiovascular (betaine) benefits; antimicrobial compounds (benzoic acid), and anti-inflammatory compounds (citrulline). Compared to uncultured controls, acid whey showed decreases in some metabolites associated with microbial metabolism and increases in others. Metabolite production was significantly affected by combinations of culturing organisms, and production location. Differences between lab-made and commercial samples could be caused by different starting ingredients, or environmental factors or both.

The growth of the Greek-style yogurt market is causing many problems for dairy companies who are trying to handle the voluminous whey by-product. Acid whey, unlike sweet whey, has a low amount of protein and high amounts of lactic acid, calcium, and other minerals. Therefore, it has limited commercial value to the food industry and often requires additional processing for disposal. Lactic acid and calcium solutions have shown efficacy in increasing the tenderness of beef and other types of meat. The purpose of this project is to investigate the use of acid whey, with its high amounts of lactic acid and calcium, to tenderize beef (eye of round, IMP 171C) during marination. This study evaluated the effects of marination of utilizing acid whey in improving quality parameters of beef. 13 roasts (Top round steaks from USDA Select steers) were randomly assigned to one of six marination treatments: (1) calcium chloride, (2) lactic acid, (3) phosphate (4) acid whey (lot 1), (5) acid whey (lot 2), and (6) control. Steaks were marinated in vacuum pouches, aged for 48 hours, cooked to 70º C and evaluated by a consumer sensory panel and other quantitative tests (texture analyzer, colorimeter, collagen, cook loss, and pH). Marination with acid whey increased the tenderness and juiciness ratings without decreasing hedonic liking scores for the overall flavor or aftertaste of the beef samples.