No abstract

Organic acids and their changes during peach (I'rum4.s persica L. Batsch) fruit ripening were quantified by HPLC for clingstone cultivars, 'Babygold 5' and 'Babygold 7', and a freestone cultivar, 'Cresthaven'. At full maturity, 'Babygold 5' and 'Babygold 7' had about 60% malic, 20% citric and 19% quinic acid; whereas 'Cresthaven' had similar amounts of all three organic acids (37, 3.5 and 28%, respectively). During fruit ripening, 'Babygold 5' and 'Babygold 7' increased in malic acid and decreased in citric and quinic acids, whereas, 'Cresthaven' showed little change in these organic acids.

Black and white plastic rowcovers were established over field-grown `Jersey Giant' asparagus (Asparagus officinalis L.). Spears were cut for 7 weeks. Season soil temperatures were lowest under white plastic and highest without plastic covering. Night air temperature under plastic covers was ≈ 1.4C higher than without plastic covering (control), but day air temperature was typically 10C higher under black plastic, with temperatures under white plastic intermediate. Marketable yield (t·ha-1) was improved with the use of plastics as was total yield (P = 0.05), but spear number/ha was similar in all treatments. There was no consistent treatment effect on spear diameter. Average spear weight was higher when under plastic, whereas spear length was reduced compared with uncovered spears. There were no differences among treatments in spear fiber content, but spears grown under plastic covers were higher in soluble solids content, titratable acidity, and nitrate and lower in protein, ascorbic acid, and total phenolics than uncovered spears. Quantitative differences in these constituents were also a function of whether they were from the upper, middle, or lower spear segment. Very little chlorophyll and carotenoids were produced in the absence of light, but there was a chroma (color intensity) difference between spears grown under the two plastics.

Clingstone peach [Prunus persica (L.) Batsch cv. Allgold] trees were fertilized once with 45 or 90 kg N/ha at budbreak or twice with 22.5 or 45 kg N/ha at budbreak and after harvest. A nonfertilized control was included. Fruits from all treatments were made into puree, and objective and subjective qualities were evaluated. Puree from the N treatments and the control did not show significant differences in Color Difference Meter (CDM) `L' and hue angle, pH, titratable acidity (TA), soluble solids concentration (SSC), SSC: TA ratio, viscosity, ascorbic acid, Ca, K, phenolic and nitrates concentration. Puree from the control and 22.5 kg N/ha applied twice had significantly lower CDM `a', `b', and chroma values than from the other treatments. The split applications of N significantly reduced levels of Ca and ascorbic acid. N rate and number of applications interacted for `a' and K. When N was applied twice at 22.5 kg·ha-1, `a' and K decreased, but this response was absent when N was applied twice at 45 kg·ha-1. Puree from the nonfertilized control was rated lower by panelists for sensory quality than that from the fertilized trees. Peach puree from trees fertilized once with 45 kg N/ha at budbreak had the best overall sensory quality.

The effect of long-term storage on the stabiliry ofpasteurized (PA) or sodium benzoate (SB) (0.1 X) treated peach puree was studied. Color, viscosity, soluble solids, pH, titratable acidity, sugars and organic acids were monitored over 4 months. Yeasts were the major microorganisms causing spoilage in nontreated peach puree. Storage at 2C increased the holding time of the control to 17 days compared with 3 days at 2SC. No yeast or other microorganisms were found in PA or SB treated puree held at 2 and 25C, for 120 days; the most significant change observed was a gradual browning. Cold temperature storage slowed down the browning. Other compositional changes were minimal. Pasteurized or SB puree stored at 25C for 4 months showed a decrease in sucrose and an increase of glucose andfructose. Malic, citric and quinic acids were stabilized by SB. Pasteurization or use of SB may be valuable for holding partially processed peach puree.