The amount and type of antioxidants present in raspberries is dependent upon cultivar, ripeness, and growing conditions. Previous research on raspberry jam has reported some color, antioxidant, and flavor loss after processing and storage, though it is unknown to what extent similar changes will occur in raspberries grown in Utah. Sugar concentration and heating temperature as well as storage time were evaluated in an effort to maximize color retention, flavor, antioxidant content, shelf life, and consumer acceptance of Utah-grown raspberry jam. Four types of jams were processed in two batches each: low-sugar (40-42 Brix) and typical sugar (65-68 Brix) at 85 and 95 C, from two separate farms in Utah. Oxygen Radical Absorbance Capacity (ORAC), total anthocyanin content (TAC), color, headspace, Brix, pH, consistency, and water activity were measured in fresh jam, and after one and three months of typical storage (dark, room temperature) to evaluate changes after storage. A sensory analysis compared three-month stored jam to fresh jam made from the same berry crop. ORAC significantly declined in all jams during storage. Fresh low-sugar jam was found to contain higher ORAC values than high-sugar jam after processing and after three months of storage. All jams retained their initial anthocyanins over the first month and significantly lost an average of 28.8% anthocyanins between months 1 and 3 of storage. Color loss was found to be less pronounced than anthocyanin degradation, though nearly all jams maintained initial L*, C*, and h* values over the first month then significantly decreased by the third month of storage. When comparing fresh and three-month jam, significant sensory differences were found in color, overall acceptability, flavor, and texture. All parameters scored higher for freshly-made jam, though three-month stored jam was still found to be acceptable to consumers. In summary, after three months of storage, significant nutrient quantity and sensory quality remains in Utah raspberry jam, despite significant declines in several assays and significant differences between treatments.



College and Department

Life Sciences; Nutrition, Dietetics, and Food Science



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Raspberries, jam, processing, heating, temperature, antioxidant content, ORAC, color, anthocyanins, storage, stability