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Keywords

Antioxidants, polyphenolics, oxidative stress

Abstract

Fresh blueberries have received much attention due to their positive role in human health and disease prevention. The abundance of polyphenolics, namely anthocyanins and procyanidins, is thought to play an important role in health promotion. Due to seasonal availability and limited shelf-life, blueberries are commonly preserved and consumed in various thermally processed forms (jams, juices, canned whole fruit, and purées). Both conventional high sugar and sugar-free blueberry jams are available on the market, but no information is available on how different formulations, processing conditions, and storage of processed jams affect the retention of polyphenolics and antioxidant capacity found in fresh berries. In this study, fresh blueberries were processed into conventional and sugar-free jams, and stored for 6 months at 4°C and 25°C. Jams were analyzed 1 d after processing and after 2, 4, and 6 months of storage for anthocyanins and procyanidins by HPLC, percent polymeric color, and oxygen radical absorbing capacity (ORAC). Anthocyanins in conventional jams were more susceptible to degradation and polymerization during storage than anthocyanins in sugar-free jams, which may be associated with elevated sugar content. Higher levels of polymers in conventional jams resulted in higher ORAC values, indicating that the polymers formed during storage possess potent antioxidant capacity. However, more research is needed to characterize the anthocyanin polymers and assess their bioavailability. Anthocyanin pigments were much more stable in sugar-free jams indicating that the low calorie jams are a healthy alternative to conventional jams. Anthocyanins, procyanidins, and ORAC were better retained in jams stored at 4°C than at 25°C indicating blueberry jams should be stored under refrigeration in order to maximize retention of health-promoting antioxidants.

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