Master of Science (MS)


School of Nutrition and Food Sciences

Document Type



The order and combination of juicing steps can change a blueberry’s bioactive phytochemicals and effect juice recovery. In addition to physical treatments such as pressing, recovery is also affected by heat and enzymes steps. Not optimizing juicing methods affect juice quality and leave many bioactive components in the press cake. To evaluate pre-press treatments, southern highbush and rabbiteye blueberries were individually pressed in a bench top press at varying temperatures. The temperature treatments included fresh, thawed, frozen and heating to 95 °C. Two pectinase enzymes, Rohapect 10L and Pectinex BEXXL, were individually used to assess impact on juice extraction. Juice recovery was averaged from three press replications for each treatment. Frozen berries which were heated to 95 °C and treated with enzyme had the highest recovery at 68.6 ± 1.1%. This process was then transferred to a pilot scale press. Pilot scale juice recovery was calculated at 74.0 ± 0.9%. Using data from the initial pilot presses, a full pilot scale experiment was triplicated. ‘Tifblue’ rabbiteye blueberries were heated in a steam jacketed kettle to 95 °C for three minutes followed by a Rohapect 10L enzyme treatment before pressing. The resulting juice from the pilot press was then filtered and pasteurized. Unfiltered juice was also pasteurized. Press cake was collected and frozen. Samples of raw berries, filtered and unfiltered juice, pasteurized juice, and press cake were taken to identify anthocyanin compounds and changes caused by juice processes using LC-MS/MS. Samples were also hydrolyzed for anthocyanidin quantification using UPLC-UV. Ten major anthocyanins were identified, including 5 arabinoside and 5 pyranoside anthocyanins and three minor anthocyanins. The five anthocyanidins, cyanidin, delphinidin, malvidin, peonidin, and petunidin, were quantified. Raw berries and press cake contained the highest anthocyanidin contents with 85.1 mg/100 g and 265.6 mg/100 g respectively. Decreases of 67% loss after pressing and 10% loss after pasteurization were determined for anthocyanins and anthocyanidins in juices. However, three new conjugated anthocyanins were found in processed juices which have not previously been reported in rabbiteye. This contributes to the value and interest of press cake for use in other food and non-food products.



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Committee Chair

Losso, Jack N.



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Life Sciences Commons