Developing functional food products through novel processing, ingredient, and shelf stability evaluation
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The purposes of this dissertation research were: 1) to develop new functional food products for consumers, 2) to evaluate processing or storage stability, antioxidant activity, and health properties of polyphenolic compounds in functional products, and 3) to determine the effects of processing from emerging technologies on properties of functional products. Novel functional food products were developed, which included a beverage made from fruit juice and high-procyanidin sorghum bran for the metabolic syndrome or diabetic markets, and model green tea (GT)-fortified apple products designated for low- and intermediate-moisture food systems. The stability of phytochemicals and antioxidant activity was evaluated in GT-fortified apple product over storage in low- and intermediate-moisture systems. Phytochemical degradation was modeled using a pseudo-first-order kinetic model (ln C = A∙e-kt). GT catechins including catechin (C), epicatechin (EC), epigallocatechin (EGC), epigallocatechin gallate (EGCG), and epicatechin gallate (ECG) showed varying levels of stability with k = 0 to 0.070, indicating degradation over storage. Analysis of water mobility by differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) supported analytical determinations that increasing moisture content related to increases in magnitude of k. The onset glass transition temperature (Tgo) of GT-fortified apple products decreased from 13°C to -34°C from aw 0.11-0.56, respectively. Low-field 1H NMR analysis of GT-fortified apple products conducted by free induction decay (FID) showed increasing relaxation times from 60 to 1,000 µs from aw 0.11-0.75, respectively. Antioxidant activity determinations including total polyphenolic content by the Folin-Ciocalteu method, 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl radical (DPPH) scavenging activity, and ferric reducing/antioxidant power (FRAP) assay conducted on extracts from high-procyandin sorghum beverage and GT-fortified apple products demonstrated value-added potential of functional ingredient incorporation to products. As an in vitro marker for diabetic systems, extracts from high-procyanidin sorghum beverage and GT-fortified apple products showed efficacy in inhibiting glycation of bovine serum albumin. High-pressure throttling was investigated as an emerging technology used for the processing of functional beverages. Apple juice inoculated with Zygosaccharomyces bailii, common spoilage yeast in fruit juices, processed by high-pressure throttling was found to have 7-log reductions in vegetative cells from processing of juice.