Effects of rootstocks and irrigation levels on grape quality of Vitis vinifera L. cv. Shiraz

The influence of two rootstocks (SO4 and 1103P) on grape quality and berry chemical composition was studied in a factorial experiment, in field grown grapevines of cv. Shiraz (Vitis vinifera L.), subjected to five irrigation levels [0% (T1), 25% (T2), 50% (T3), 75% (T4) and 100% (T5) of irrigation depth (IW, mm): Class A pan evaporimeter (CPE)]. Spectrophotometric analyses of total anthocyanins (TA), total phenolics (TP) and total antioxidant activity (AA) in grape extracts were performed. Also, total soluble solids (TSS), total acidity, pH, total sugar content, ash, juice yield and color index of red grapes (CIRG) of berry samples were determined. TA, TP, AA, TSS, total sugar content, ash, and CIRG valuesdecreased together with increasing irrigation levels. On the contrary, T4 and T5 irrigation treatments increased total acidity, pH and juice yield of samples compared to the effects of T1, T2 and T3 irrigation treatments for both rootstocks. Moreover, T1 or T2 treatments caused an increase in TA, TP, AA, TSS, total sugar content, ash, and CIRG index values of grape samples in comparison to that of vines irrigated with T3, T4 and T5 levels. Grape quality response to irrigation levels was altered by rootstocksand quality of grapes harvested from vines grafted on SO4 was higher compared to those from 1103P under all irrigation treatments. Based on the findings, it was suggested that T2 irrigation level might be sufficient to guarantee Shiraz yield potential without significant loss in grape quality under the study conditions. Also, the results make it possible to recommend use of SO4 rootstock under non-limiting water conditions because of its positive on grape quality parameters, while 1103P might be better choice under water-limiting conditions

Study on the development of pomegranate juice processing technology: Clarification of pomegranate juice

PubMedID: 14609083The effects of clarification agents and methods on pomegranate juice quality were studied. Fruits were pressed as whole, and extracted juice was clarified with gelatin, polyvinylypolypyrrolidone (PVPP) and natural sedimentation. In order to determine the effects of these clarifying techniques on product quality, pH, total phenolic substances (TPS), anthocyanin, turbidity, and total colour density tests were applied to each sample. In clarification, the main purpose was to reduce the amount of phenolic substances. Phenolic substances were controlled in each clarification method. The most effective method was the application of 1 g/L gelatine for clarification. Sensory evaluation also applied for clarified juices and gelatin application was selected by panelists to be superior

Study on the development of pomegranate juice processing technology; the pressing of pomegranate fruit

In this research, the effects of pressing on pomegranate juice quality were studied. Fruits of three different cultivars were pressed at different pressures, times, and shapes as a whole, parts and sacs only. Juice yields increased up to 49% depending on pressure, time and cultivar but such juice was of excessive astringency and bitterness. Astringency and bitterness are mostly attributed to phenolic substances. These substances pass through juice by size reduction of the fruits before pressing. Thus, best results in pressing were obtained by using whole fruits compared with juice sacs and size reduced pomegranates. Amounts of phenolic substances in fruit juice are increased by increasing presssure. It was evaluated that it would not be feasible for both phenolic substance and pressing cost, if the pressure is taken over 10 kg/cm2

Organic Acids, Sugars, and Anthocyanins Contents in Juices of Tunisian Pomegranate Fruits

peer reviewedJuices made from fruits of 30 Tunisian accessions of pomegranate were studied for their organic acids, sugars, and anthocyanin contents, using high performance liquid chromatography. Among the detected organic acids, malic acid was the major one (>50%) followed by citric acid (>22%), while among sugars, fructose and glucose were most present in pomegranate juice contributing 53.9 and 43.4% of the total sugar content, respectively. The total anthocyanin content ranged from 9-115 mg per litre of juice with the following ranges of the six compounds found: cyanidin-3,5-diglucoside (3.1-74.4 mg/L), delphinidin-3-glucoside (0.7-22.0 mg/L), cyanidin-3-glucoside (0.8-21.0 mg/L), pelargonidin-3-glucoside (0.5-16.1 mg/L), pelargonidin-3,5-diglucoside (0.0-11.8 mg/L), and delphinidin-3,5-diglucoside (0.0-5.4 mg/L). Based on the analyzed parameters, cluster analysis allowed grouping cultivars into two main clusters. One was made of sour cultivars and the second of the sweet ones. Principle component and cluster analyses suggested that the composition of the pomegranate fruits is determined by cultivar rather than cultivation location