Aseptic processing and storage of grape juice for winemaking

The objective of this dissertation research was to develop a process to preserve grape juice so that wine can be produced throughout the year.;Grape juice deteriorates during storage due to enzymatic browning, non-enzymatic browning, unstable proteins and microorganisms. The most common methods used for preservation of grape must to overcome the deterioration effects can be divided into two categories; preservation of juice with chemical additives and using physical processes like heat and membranes. The emerging juice preservation technologies considered for preservation of grape juice were hyperbaric pressure, high intensity pulsed electric field, irradiation, oscillating magnetic fields, high intensity pulsed light radiation, chemical preservatives and membranes.;The present study investigated the effect of ultrafiltration membranes with molecular weight cutoffs (MWCO) of 30,000 Daltons and 100,000 Daltons and microfiltration membranes with a 0.1 micron pore size and 500,000 Daltons on French Columbard and Chambourcin grape juice characteristics. Pilot plant studies were performed on 100,000 Daltons membranes. The feed, permeate and retentate were analyzed for pH, titratable acidity, 0Brix, sugars and acids, free SO2, anthocyanins, microorganisms, browning and total soluble phenolics. The juice was aseptically stored for three monts and shelf life studies were performed on permeates collected from 30,000 Daltons, 100,000 Daltons and 0.1 micron membranes.;The 30,000 Daltons, 100,000 Daltons and 0.1 micron pore size membranes could successfully remove microorganisms from grape juice. However the 500,000 Daltons membranes could not retain all microorganisms. There was no significant change in juice characteristics for all the membranes except for 30,000 Daltons membrane. The 30,000 Daltons membranes had high rejection coefficients for phenolic compounds. Juice processed by 30,000 Daltons, 100,000 Daltons and 0.1 micron membranes was shelf stable. A process flow diagram consisting of feed tank, collection tank, heat exchanger, 100,000 Daltons membranes and a 0.1 micron membrane safety filter was developed for aseptically processing grape juice and pilot plant studies were performed using the 100,000 Daltons membranes. Finally the control juice, permeate and the juice stored for 3 months were fermented to produce wine. The wine was evaluated by a sensory panel from a major winery. The report from the sensory panel was that there was no significant difference between the wine made from control juice, permeate and juice stored for 3 months.