Location: Dairy and Functional Foods Research
2023 Annual Report
Objectives
Objective 1: Use process simulation to develop cost-effective processes for valorization of waste dairy streams to reduce environmental impact and reuse water.
Objective 2: Investigate technologies for large-scale production of edible coatings, made from predominately dairy proteins and waste dairy streams; their storage stability; and, as films for secondary packaging.
Objective 3: Develop fermentation technologies for utilizing dairy coproducts or waste streams to produce antimicrobial peptides by lactic acid bacteria, and assess their activity against bacterial pathogens and spoilage microorganisms.
Objective 4: Develop a process for recovering food-grade, allergen-free fat from frozen dessert waste.
Approach
Dairy processing generates waste streams ranging from those that are mostly water to packaged products that did not meet a manufacturer’s quality standards. This project aims to utilize the watery acid whey streams generated from Greek-style yogurt (GSY) manufacture, cheese whey, permeates, and wasted products such as ice cream through computer simulation and laboratory and pilot plant research. Computer simulation of an actual GSY plant will be used to investigate ways to recover and reuse water from the waste streams and for optimizing extraction of nutrients with economic value. The model will be customized by choosing conditions for straining based on the properties of a finished GSY with properties that consumers appreciate using knowledge-based systems and advanced simulation methods. Laboratory and pilot plant experiments will examine the manufacture of edible films and coatings from the watery streams for food and nonfood uses by standardizing the feed material used for each type of film. Other research will determine if the dairy waste streams or byproducts can be utilized as fermentation substrates for the production of antimicrobial peptides by dairy lactic acid bacteria. Preliminary studies will seek to optimize antimicrobial peptide production by varying substrate composition and fermentation parameters. Additionally, molecular techniques will be investigated for developing bacterial strains capable of producing higher concentrations of antimicrobial peptides, and fermentates will be assessed for novel antimicrobial peptides generated via the degradation of native milk proteins. Fermentation technologies will be assessed for pilot-scale production of antimicrobial peptides and resulting fermentates will be investigated for food safety and functional food applications. Finally, research will determine whether allergen free butterfat can be recovered from waste ice cream using a cost-appropriate process. This will be accomplished by studying the stages of fat separation and refining individually, and at each stage testing a variety of technologies for efficacy and projected cost. Pilot plant implementation of the chosen technologies will be used along with techno-economic analysis to generate results that enable ice cream manufacturers to evaluate the process for possible adoption. This project will introduce several sustainable approaches for reducing energy and water use, and recovery of process wastes with added value for food or nonfood uses.
Progress Report
Under Objective 2, work has begun on using a newly purchased 3D bioprinter to print milk-based substrates to form edible structures. A literature search yielded a list of dairy based recipes, most including the main milk protein casein as an ingredient, with potential for use as 3D printing substrates. These recipes were tested in the 3D printing setup. Optimization of recipe components and 3D printer conditions will be needed to make structures that maintain quality and strength over time under various storage conditions. However, cross-linking (covalently bonding protein units) was determined to be vital for printed structures that maintain shape. Three of the tested recipes show promise for future use after modifications, with each of these employing a different cross-linking technique. Additionally, work on increasing the efficacy of calcium caseinate based films through pH adjustment was completed demonstrating effective conditions for film production.
Under Objective 3a, research focused on the characterization of antimicrobial compounds naturally produced by dairy starter cultures. Results showed the production of multiple antimicrobial peptides in both Streptococcus thermophilus strains ST134 and B59671. Collaborative studies are ongoing with Carnegie Mellon University to characterize the molecular mechanisms regulating antimicrobial activity in ST134, and in-house comparative genomic studies are in progress to identify regulators of antimicrobial production in B59671. Once these genetic processes are better understood, strategies for increased production of the antimicrobial peptides can be developed. Additionally, research has shown that an aqueous co-product generated during the extraction of fat from waste ice cream can be fermented by dairy cultures or food-grade yeast to produce antimicrobial compounds or alcohol respectively. The antimicrobial compounds produced from waste ice cream will be explored as functional ingredients within animal feed. Under Objective 3b, Lactobacillus species were used to ferment skim milk (= 96 hr), resulting in the production of broad-spectrum antimicrobial compounds. These antimicrobial activities were only observed when skim milk was used as the fermentation substrate, suggesting they may be milk-derived antimicrobial peptides released by the degradation of milk proteins. Characterization of these antimicrobial compounds is ongoing.
Under Objective 4, multiple options for the recovery of fat from waste ice cream (WIC) were investigated. Researchers proved that churning is a viable approach. Although theory suggests that waste ice cream will be difficult or impossible to churn, studies showed that using carefully selected temperatures, the fat globules in WIC can be joined into a solid mass using moderate amounts of energy and inexpensive equipment. Separately, prior year success in use of enzymes and gravity effects to destabilize WIC and concentrate fat content was continued. In the current year, these techniques were incorporated into a process which yields free oil which is suitable to process in conventional edible oil refining systems. Finally, a novel process utilizing only food-compatible solvents and salts was shown to destabilize the WIC emulsion and allow for the recovery of high-quality fat.
Accomplishments
Review Publications
Garcia, R.A., Plumier, B.M., Lee, C., Liang, C. 2023. Passive separation of waste ice cream. International Dairy Journal. https://doi.org/10.1016/j.idairyj.2022.105570.
