Quality Of Niagara Grape Juice And New York Wines: Effect Of Additives, Thermal Processing, Cold Stabilization, And Filtration
We aimed to improve the quality of grape juices and wines by using natural antimicrobials and processing techniques to reduce sulfite usage and anthocyanin losses, and by utilizing crossflow filtration to increase sustainability. We evaluated harvest and processing methods to improve the quality of bottled Niagara grape juice stored at 18°C. Handpick vs mechanical harvest, early and late harvest date, potassium metabisulfite vs ascorbic acid (AA) addition (antioxidants), aeration and fining agents effect, hot-break prior pressing, filtering conditions and hotpack temperature, were evaluated. Late harvest juices had better quality. AA juice quality was comparable to sulfited juices, thus AA could be used as sulfite substitute. Hot-break juices had significantly higher phenolic and antioxidant capacity, lower turbidity and brown color than traditional cold-pressed juices; however, hot-break juices darkened faster over time. Harvesting method, hot-pack and hot-break temperature did not affect juice quality. Compared to traditional diatomaceous earth (DE) filtration, 500 kDa polymeric crossflow membrane filtered-juices had lower turbidity and brown color. Ceramic membranes produced juices with comparable quality to DE. Fining agents partially removed browning precursors but were not as effective as sulfite in browning prevention. The effectiveness of traditional and natural antimicrobials for shelf-life extension in cold-filled Niagara juices (still and carbonated) inoculated with yeast was assessed. Best results were obtained with 250 ppm dimethyl dicarbonate alone or in combination with 5-10 ppm natamycin for shelf-life extension comparable to juices with 0.05% sorbate/benzoate of about 160 days. Ceramic and polymeric crossflow membrane microfiltrations for 4 NY red and white wines were evaluated against DE. All filters produced microbiologically stable wines with comparable quality, but only ceramic membrane wines were perceived similarly to DE. For tank bottoms (higher solids content), ceramic membrane filtration represented a more sustainable operation. Loses of anthocyanins with potassium bitartrate (KHT) coprecipitation during cold-stabilization were largely controlled by pH of model solutions. Loses were minimized when pH [LESS-THAN OR EQUAL TO] 2.95 which was likely due to neutralization of negatively charged KHT crystal surface. Anthocyanin coprecipitation decreased as potassium concentration increased, indicating both compounds were competing coprecipitation. Rutinosides were less likely to coprecipitate than glucosides. for
Niagara grape juice processing; Cross-flow filtration
Padilla-Zakour, Olga I.
Sacks, Gavin Lavi; Worobo, Randy W.
Food Science & Technology
Ph.D. of Food Science & Technology
Doctor of Philosophy
dissertation or thesis