physical characteristics, quantitative-qualitive properties and anti-oxidant materials of local orange (citrus sinensis cv. siavaraz) at harvesting times, during processing and storage

introduction: citrus fruits, which belong to the family of rutaceae are one of the main fruit tree crops grown throughout the world. although sweet orange (citrus sinensis) is the major fruit in this group accounting for about 70% of citrus output.citrus fruits are well – appreciated fortheir refreshing juice and health benefits.the health benefits of citrus fruits are linked to the high amounts of photochemical and bioactive compoundssuch as flavonoids, carotenoids, vitamins and minerals available in their juice.these phytonutrientsmay act as antioxidants, stimulate the immune systems; induce protective enzymes in theliver or blockthe damage of the genetic materials. the phytonutrients and vitamins may be responsible for theantioxidant, anticancer and anti-inflammatory properties of the citrus species.citrus fruits processing accounts for approximately one third of total citrus fruitproduction, more than 80% of it is orange processing, mostly for orange juice production.the most important processed citrus fruits product isorange juice. orange juice can be presented in different forms. the major types of orangejuice are the freshly squeezed orange juice and concentrated orange juice.siavaraz local orange is an orange cultivar grown in north of iran which is used mainly in orange juice production. there is no systematic study about the relation between physical characteristic of fruit at harvest time and its juice quality and quantity. materials and methods:in this study, the physical characteristics, quantitative-qualitive properties of siavaraz local orange at harvesting times and changes in anti-oxidant components of its juice during processing and storage were investigated.the fruit were collected in eleven different harvest time (start of fruit harvesting and every two week intervals) and different parameters including fruit length, diameter, spherical coefficient, density, peel thickness, juice percentage, total soluble solid (tss),titrable acidity(ta) were evaluated. in next stage ascorbic acid, total phenolics and anti-oxidant capacity of different fruit juice include fresh squeezed juice by hand and extractor, juice reconstituted from orange concentrate with 60° brix, juice reconstituted from orange concentrate with 65° brixwere evaluated and compared. finally, changes in vitamin c content during refrigerated storage infresh squeezed juice by hand andjuice reconstituted from orange concentrate were measured. results & discussion:results showed that siavaraz local orange was in four size with different physical characteristics. the highest amount of density was belonged to small fruits with 0.977 at the first harvest stage. small oranges with lowest peel thickness had the highest juice percentage but the large oranges with the higher tss showedhigher production efficiency (327.24%). the ta and ph in first stage of harvest were the highest and the lowest, respectively compared to other stage. the highest concentrate efficiency (6.42%) and juice quality (9.88° brix) were obtained at the harvest stagenumber six and seven, respectively. the lowest amount of juice percentage for concentrate production was observed at the stagenumber six (15.6 kg). by investigating the anti-oxidant compounds, results reveals that ascorbic acid and anti-oxidant capacity of juice taken by juicer extractor, were higher (p<0.05) than juices that obtained by hand. the lowest amount of ascorbic acid was observed in juice reconstituted from orange concentrate with 65° brix (46.73 mg.100ml-1) while the highest ascorbic acid content was measured in juice taken by juice extractor (60.54 mg.100ml-1).vitamin c reduction in juice reconstituted from orange concentrate with 60° and 65° brixwas reduced 12% and 22.8%m respectively compared to orange juice in storage tank. the reduction in vitamin c due to heat treatment was more significant than other factors. there was a direct relation between vitamin c and phenolic content with antioxidant capacity of juice and the highest antioxidant capacity were observed in juice taken by extractor (53.35%). furthermore there were no significant differences between anti-oxidant capacity in orange concentrate with 65° and 60° brix. the antioxidant capacity in orange juice before heat treatment well correlated with vitamin c content. the phenolic components showed the minimal decline during processing compared to vitamin c. it seems that some compounds which arise from heat treatment of juice may exert some antioxidant property in final products. reduction of ascorbic acid content in orange juice that reconstituted from concentrate was higherthan hand squeezed juice stored in refrigerator temperature. it can be concluded that by using proper managing system in harvest, processing and storage it is possible to optimize final product quality.