The factors affecting postharvest color losses in Concord grapes were investigated, with emphasis on the extraction, partial purification and characterization of naturally occurring enzymes that may be involved. Color losses were accelerated in Concord juice by the crude enzyme extracted from the grapes. Catechol was oxidized more rapidly than other o-dihydroxyphenols, although pyrogallol, caffeic acid and dl-DOPA were good substrates for the crude polyphenoloxidase (PPO). The optimum activity was in the pH range 5.9-6.3 and at temperatures 25-30°C. Kinetic data for the crude enzyme showed a Michaelis constant of 67 mM of catechol at pH 6.0. Effective inhibitors were Na, S, 0,, dithiothreitol, phenylhydrazine, cysteine and others. Peroxidase (PRO) activity of the crude extract was very low in ripe Concord grapes. Anthocyanin pigment degradation by the crude enzyme extract was dependent on maturity of the grapes. The most rapid degradation of pigment occurred when crude enzyme from ripe grapes was added.

A study was conducted to determine the effects of cultivar, root size, cooking method and storage on carbohydrates and quality attributes of sweet potatoes. Roots were analyzed after curing and after 7 months storage for sugars, starch, pectins, hemicellulose, cellulose, gscorbic acid, and carotenoids. Sensory evaluations were also conducted. 'Centennial' and 'Jasper' contained the highest percentages of total sugars, starch, water-soluble pectin, hemicellulose and carotenoids, while 'Georgia Jet' was lowest in all carbohydrates except reducing sugars and water-soluble pectin. Baked and microwave cooked roots were highest in most of the carbohydrates; h&w-ever, canned roots were higher in starch because of the rapid inactivation of amylase during cooking. Boiled roots were lower in carotenoids while canned roots were lowest in ascorbic acid. There was a decrease in reducing sugars, starch, pectins, hemicellulose, and cellulose during 7 months storage. Sensory ratings for color intensity and attractiveness corresponded to carotenoid content, CDM 'L' value, and hue angle (orangeness). Roots of different cultivars, size and storage period responded differently to cooking methods, thus producing significant interactions. Baking produced the highest quality cooked product as compared to other cooking metliods.

The study was conducted on canned dry beans including 8 types, 2 moisture levels, 4 blanching treatments, and 4 storage times. Low original moisture level before soaking resulted in higher hyration ratios in all bean types except Pinks and Avenger. Drained weights were higher in bean types that had lower shear press readings. Beans blanched in steam and lots containing 16% initial moisture were firmer in texture. Blanch method did not affect % splits, but type and storage time created significant differences. There were differences among types in riboflavin and vitamin E. Both vitamins decreased during storage of canned beans, but only riboflavin was lower in beans of 16% moisture, and blanched in steam as compared to water. Carbohydrate composition was significantly different between types of beans, but the greatest differences were in hemicellulose. Steam blanching leached out less sugars and high blanch temperatures increased the solubility of cellulose. Dwarf Horticulture #4 rated highest in quality followed by Red Kidney, Navy and Pinto.

No abstract

Three types of beans, Pinto, Red Kidney and Dwarf Horticulture #4 were soaked for different time intervals, canned in either water or tomato' sauce, and stored for 3 and 6 months. The types of beans reacted differently to soaking and processing. Pinto was higher in drained weight (dr wt) and lower in shear press firmness than Red Kidney and Dwarf Horticulture #4. Riboflavin and Vitamin E were lowest in Red Kidney, but percent splits were higher. Soaking time before blanching affected dr wt and Riboflavin, but not other quality attributes. There was no difference in hydration ratios after blanching except in those beans that were not soaked. Beans canned in tomato sauce were much firmer and were higher in riboflavin. Strong interactions between the main effects of type, canning media, soak time and storage time influenced the decision for recommending any one soak time or canning media for all types of beans unless other processing conditions are altered.THE TYPES of beans for this study were harvested in August, 1974, from plots located at the Main Experiment Station, University of Arkansas, Fayetteville, Ark. The dried beans were stored for 6 wk after harvest in a dry, air-conditioned room at 24°C. Moisture content was determined and the lots of beans were then stored in sealed plastic containers at 5°C to maintain the present moisture level of approximately 11%.