44C-21 |
Effects of processing temperature on anthocyanins, total phenolics and antioxidant activity of bilberry (Vaccinium myrtillus L.) juice during storage |
G. SKREDE1, R. F. Høines, and K. Aaby. (1) Food Products and Raw Materials, MATFORSK, Norwegian Food Research Institute, Osloveien 1, Aas, N-1430, Norway Bilberries (Vaccinium myrtillus L.) are among the riches sources of anthocyanins and other polyphenols. These compounds are of interest because of the positive health benefits associated with their antioxidant ability. During processing of juice, antioxidants are susceptible to degradation by endogenous enzymes. Adjusting processing and storage conditions to facilitate high retention of active components are important when healthy products are focused. The present study was undertaken to investigate effects of heating bilberry mash prior to depectination, on retention of anthocyanins, total phenolics, and antioxidant activity when processing bilberry juice under industrial-like conditions. Further, the stability of these compounds during storage was of interest. Frozen Norwegian wild bilberries were thawed, cut, heated to 43, 60, 75 or 95 °C and cooled to 43 °C. Depectination with commercial enzymes were performed before pressing the mash. Pasteurized, single-strength juice was stored at 4 or 20 °C for 38 weeks. Monomeric anthocyanins, total phenolics (GAE), and antioxidant activity (DPPH) were determined in berries and in juice during storage (0, 6, 12, 38 weeks). Anthocyanin levels of juice from bilberry mash heated to 43, 60, 75 or 95 °C were 155, 192, 244 and 297 mg/100g, respectively. Frozen berries contained 416 mg anthocyanins/100 g. GAE in juice increased from 1980 to 3250 mg/100 g by increased heating. Antioxidant activity of juice increased similarly. By storage at 4 °C for 38 weeks only minor decreases in anthocyanins and GAE occurred while decreases by storage at 20 °C were above 50% in all juices. Antioxidant activity remained stable, or even increased, during storage. The findings demonstrate that large improvements in juice quality are obtained by introducing an early heating step during processing and by cold storage of juice. Adjusting processing practice may thus improve retention of the naturally occurring healthy compounds of berries.
Session 44C, Fruit & Vegetable Products: Chemistry
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