This study evaluated the effects of processing and 6 mo of storage on total monomeric anthocyanins, percent polymeric color, and antioxidant capacity of blueberries that were canned in syrup (CS), canned in water (CW), pureed, and juiced (clarified and nonclarified). Total monomeric anthocyanins, percent polymeric color, and oxygen radical absorbing capacity (ORAC) assay using fluorescein (ORAC(FL)) were determined postprocessing after 1 d, and 1, 3, and 6 mo of storage. Thermal processing resulted in marked losses in total anthocyanins (28% to 59%) and ORAC(FL) values (43% to 71%) in all products, with the greatest losses occurring in clarified juices and the least in nonclarified juices. Storage at 25 degrees C for 6 mo resulted in dramatic losses in total anthocyanins, ranging from 62% in berries CW to 85% in clarified juices. This coincided with marked increases in percent polymeric color values of these products over the 6-mo storage. The ORAC(FL) values showed little change during storage, indicating that the formation of polymers compensated for the loss of antioxidant capacity due to anthocyanin degradation. Methods are needed to retain anthocyanins in thermally processed blueberries.

Blueberry fruits from five commercial cultivars and 13 breeding selections grown at the same locations over two growing seasons were analysed for total phenolics (TPH), total anthocyanins (ACY), total hydroxycinnamic acids (HCA), total flavonols (FLA), fruit weight and oxygen radical-absorbing capacity (ORAC). Variation in ORAC, TPH, ACY, HCA, FLA and fruit weight among genotypes was much greater than that observed between growing seasons, indicating that genetics plays a more important role than growing season in influencing ORAC and phenolic content in blueberries. Significant main effects for growing season and genotype × growing season observed for ORAC, ACY, HCA and fruit weight demonstrate that environmental growing conditions can impact levels of phenolics and ORAC in blueberries and that certain genotypes vary in their capacity to synthesise phenolics under different growing conditions. In general, genotypes with smaller berries had higher ORAC values and levels of TPH, ACY, HCA and FLA than large-berried genotypes. Over both growing seasons, ORAC correlated highly with TPH, ACY, HCA and FLA, while fruit weight correlated inversely with all phenolics measured. Our results indicate that blueberry genotypes should be screened over multiple growing seasons in order to identify antioxidant-and phenolic-rich germplasm.

Chokeberries are an excellent source of polyphenols, but their fate during juice processing and storage is unknown. The stability of anthocyanins, total proanthocyanidins, hydroxycinnamic acids, and flavonols at various stages of juice processing and over 6 months of storage at 25 °C was determined. Flavonols, total proanthocyanidins, and hydroxycinnamic acids were retained in the juice to a greater extent than anthocyanins, with losses mostly due to removal of seeds and skins following pressing. Anthocyanins were extensively degraded by thermal treatments during which time levels of protocatechuic acid and phloroglucinaldehyde increased, and additional losses occurred following pressing. Flavonols, total proanthocyanidins, and hydroxycinnamic acids were well retained in juices stored for 6 months at 25 °C, whereas anthocyanins declined linearly. Anthocyanin losses during storage were paralleled by increased polymeric color values, indicating that the small amounts of anthocyanins remaining were present in large part in polymeric forms.

Blueberry juice processing by-products are a rich source of procyanidins, which comprise a group of compounds shown to possess numerous health benefits, including protection against coronary heart disease, type II diabetes, and obesity. Most of the procyanidins present in blueberry pomace, however, are large molecular weight compounds that are poorly absorbed and show weak bioactivity compared to the smaller molecular weight monomers and dimers. The objective of our study was to identify optimal extrusion variables to enhance the contents of monomers and dimers at the expense of large molecular weight procyanidin oligomers and polymers. Extrusion variables temperature (160 and 180 degrees C) and screw speed (150 and 200 rpm) were tested using mixtures of blueberry pomace with decorticated white sorghum flour at a ratio of 30 : 70 and 45% moisture content. Extrudates were analyzed for procyanidin composition and total anthocyanin content. Extrusion of blueberry pomace increased the monomer, dimer, and trimer contents considerably at both temperature and screw speeds. The highest monomer content, obtained at 180 degrees C and 150 rpm screw speed, was 84% higher than the nonextruded control. Significantly higher levels of dimer and trimer contents were also obtained under these conditions. Increases in monomer, dimer, and trimer contents apparently were the result of reduced polymer contents, which was approximately 40% lower for samples extruded at 180 degrees C temperature and 150 rpm screw speed. Extrusion processing reduced total anthocyanin contents by 33% to 42% indicating that additional treatments are needed to retain the pigments. These results demonstrate that extrusion processing can be used to increase procyanidin monomer and dimers in blueberry pomace.

This study evaluated the effects of processing and 6 mo of storage on total monomeric anthocyanins, percent polymeric color, and antioxidant capacity of black raspberries that were individually quick-frozen (IQF), canned-in-syrup, canned-in-water, pureed, and juiced (clarified and nonclarified). Total monomeric anthocyanins, percent polymeric color, and ORAC(FL) were determined 1 d postprocessing and after 1, 3, and 6 mo of storage. Thermal processing resulted in marked losses in total anthocyanins ranging from 37% in puree to 69% to 73% in nonclarified and clarified juices, respectively, but only the juices showed substantial losses (38% to 41%) in ORAC(FL). Storage at 25 degrees C of all thermally processed products resulted in dramatic losses in total anthocyanins ranging from 49% in canned-in-syrup to 75% in clarified juices. This coincided with marked increases in percent polymeric color values of these products over the 6-mo storage. ORAC(FL) values showed little change during storage, indicating that the formation of polymers compensated for the loss of antioxidant capacity due to anthocyanin degradation. Total anthocyanins and ORACFL of IQF berries were well retained during long-term storage at -20 degrees C.