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  • Author or Editor: Donna Chrz x
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The Stonyhard peach fruit mutation has been used to study softening and textural changes during ripening. Without ethylene exposure, firmness of Stonyhard remains fairly constant at room temperature. When exposed to 1 or 100 ppm C2H2 for 48 hours, fruits soften at a rate consistent with control fruit (`Cresthaven') to a similar firmness. However, 1 ppm—treated fruit attains a normal juicy texture, while 100 ppm—treated fruit attains a pasty texture. Control fruit softened to a normal juicy texture with either ethylene treatment. Cell wall endopolygalacturonase (endo-PG) was not detectable in Stonyhard fruit without C2H2 exposure; it increased at a rate similar to control fruit when exposed to 1 ppm C2H2, and was double that of 1 ppm for fruit exposed to 100 ppm for up to 48 hours. Low levels of endo-PG were detected in control fruit not exposed to C2H2; 1 ppm treatment led to a normal increase, which was comparable to that in Stonyhard. However, endo-PG in 100 ppm—treated fruit was very similar to that of 1 ppm for up to 24 hours, though high levels of endo-PG were observed at 48 hours. Attainment of the pasty texture in 100 ppm—treated Stonyhard fruit may have been related to release of large quantities of pectic polysaccharides as a result of the sudden increase in endo-PG activity. Work was supported by USDA grant 96-34150-2540 and the Oklahoma Agricultural Experiment Station.

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The pungency in hot peppers [Capsicum annuum (L.) var. annuum] is mostly due to two capsaicinoids, capsaicin (CAP) and dihydrocapsaicin (DC), which are amide derivatives of vanillylamine and 8-methyl-6-nonenoic acid (E) or 8-methyl-nonanoic acid (A), respectively. During our investigation of the mechanism of capsaicinoid-specific metabolism in pepper fruit, we have developed a method to extract, purify, and quantitate these fatty acids from the free fatty acid pool in placental tissue. Fresh placenta was ground using a mortar and pestle and extracted with diethyl ether. Fatty acids were methanolysed and fatty acid methyl esters were quantitated using GC with capric acid as internal standard. Capsaicinoids accumulated in the same placenta were extracted with N,N-dimethylformamide (DMF) and quantitated using HPLC. The lipid fraction had to be separated from capsaicinoids, since capsaicinoids yielded about 10% of their respective fatty acids during methanolysis. An aminopropyl column was used to separate capsaicinoids from free fatty acids. Extraction recovery for both fatty acids was greater than 70%. This procedure is being used to quantitate fatty acid precursors for capsaicinoid biosynthesis in pepper placenta. We will demonstrate use of this procedure with pepper selections varying in CAP/DC ratio to evaluate the effect of metabolic precursors on capsaicinoid metabolism.

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Pecans, because of their high oil and polyunsaturated fatty acid content, have a relatively short shelf life due to oxidation of the oil. Using a nondestructive supercritical CO2 extraction process, we evaluated oil reduction as a means for pecan shelf life extension. Pecan halves were extracted under sufficient conditions for 22% and 28% oil reduction, and then stored in modified-atmosphere packages with 21% O2 at 22C for up to 37 weeks. Kernel hexanal content and sensory rancid flavor were monitored at various times throughout the study. The resistance of oils to oxidation, indicated by the onset of sustained hexanal production, was increased from 6 weeks for full-oil halves, to 18 weeks for 22% reduced-oil halves, to 22 weeks for 28% reduced-oil halves. Objectionable rancid flavor was detected by the 22nd week of storage for full-oil pecans. Reduced-oil pecans never developed objectionable rancid flavor. Supported by USDA grant 93-341508409, OCAST grant AR4-044, and the Oklahoma Agricultural Experiment Station.

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The peach mutation `Stony Hard' confers a slow softening attribute to the fruit and also confers a highly reproducible predisposal of fruit to soften abnormally to a mealy texture. Induction of mealiness required continuous 48-hour 100-ppm ethylene exposure. `Stony Hard' fruit exposed to low ethylene concentrations (l ppm) or discontinuous 100 ppm ethylene softened more rapidly than fruit exposed to ethylene-free air but to a normal texture. Ethylene treatment failed to induce mealiness in selections without the `Stony Hard' gene. As quantitative methods for assessment of mealiness, mesocarp-extractable juice decreased, and buffer soluble solids and soluble polysaccharide galacturonic acid content increased for mealy fruit. `Stony Hard' peach fruit represent the only known system in which the concentration and duration of exposure to ethylene can be used to manipulate softening and textural properties of the fruit. Supported by U.S. Dept. of Agriculture grant 93-34150-8409 and the Oklahoma Agricultural Experiment Station.

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Field experiments were conducted at Bixby, OK, in 2007. Four compost treatments and an unamended control were compared for field production of eight (spring) or four (fall) red radish (Raphanus sativus L.) cultivars. Treatments were either spent mushroom substrate or yard waste compost spread over plots to an average depth of 2.5 or 5 cm and preplant-incorporated ≈5 to 7 cm deep. Radishes were direct-seeded into prepared plots and subsequently grown using standard cultural practices. Samples of median-sized marketable storage roots were shredded and juice was analyzed in the laboratory for pungency as measured by isothiocyanate (ITC) concentration (primarily 4-methylthio-3-butenyl isothiocyanate). In the spring, mean ITC concentrations ranged from 28.2 to 36.8 μmol per 100 g juice in storage roots from the four compost treatments, and differences were not significant (α = 0.05). There were not enough storage roots to analyze from the unamended control plots as a result of herbicide toxicity. Cultivars differed in mean concentration of ITCs, ranging from a high of 52.9 μmol per 100 g juice for ‘Cherry Belle’ to a low of 19.2 μmol per 100 g juice for ‘Crunchy Royale’. In the fall, mean ITC concentrations ranged from 10.5 to 24.6 μmol per 100 g juice in storage roots from the four compost treatments. Differences were not significant (α = 0.05), and there were no differences from the control value of 17.5 μmol per 100 g juice. The mean ITC concentration was 19.9 μmol per 100 g juice for the four cultivars tested in the fall, and the cultivars did not differ. Results indicate that the tested compost treatments did not affect pungency of red radish storage roots as measured by concentrations of ITCs.

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Lycopene from ground watermelon flesh can be segregated between filtrate and filter cake by coarse filtration. Low speed centrifugation of the filtrate can further segregate filtrate lycopene between an easily recoverable precipitated high lycopene pellet and a serum. Lycopene in watermelon flesh increases steadily during maturation and remains constant, or slightly decreases in overripe melons. This study was conducted to document the effect of melon maturity on lycopene segregation during filtration/centrifugal processing. Flesh of three seedless watermelon cultivars was ground and filtered through two layers of Miracloth. Filter cakes were rinsed with water and filtrates were centrifuged at 3500 g to precipitate lycopene. Centrifugal recovery of lycopene from filtrates was about the same for undermature and mature melons (50% to 70%), but was much lower for overripe melons (35% to 45%). This decline in recoverable lycopene from overripe melons could be negated if ground flesh was heated to 60 or 85 °C prior to filtration. Lycopene from preheated flesh segregated predominately into the filter cake for all three maturity groupings. The interaction between melon maturity and pre-filtration heating will be evaluated and integrated into a potential watermelon lycopene production system.

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Six experiments were conducted on ‘Genovese’ basil (Ocimum basilicum L.) in Oklahoma to study the feasibility of establishing basil in the field by direct seeding. Variables examined included use of raw seed or pelleted seed, seeding depth, seeding rate, and comparison with transplanting. Direct seeding was done using a hand-pushed planter (first four experiments), a tractor-drawn planter (fifth experiment), or both types of planter (sixth experiment). Plants were destructively harvested by machine. Stands were established successfully using transplants or using raw or pelleted seed with a hand-pushed planter. Planting at a depth of ≈10 mm resulted in lower yields than planting at a depth where seeds barely were covered with soil (≈5 mm). Seeding rates of ≈80 seeds/m led to higher final stands and higher yields than those obtained with seeding rates of ≈30 seeds/m. These studies were not designed to test effects of plant population on basil yield, but data suggest that final stands above the common recommendation of one plant per 30.5 cm in rows spaced 90 cm apart may result in yield increases. Plots direct-seeded with the tractor-drawn planter failed to establish in the fifth experiment. Plants established using pelleted seed with the hand-pushed planter did not differ from plants established by transplanting in cumulative yields in the sixth experiment, even though the transplanting treatment allowed one additional harvest. The lowest cumulative yields in the sixth experiment came from plants established using pelleted seed with the tractor-drawn planter. Thus, direct seeding of basil was successful only with a hand-pushed planter. While direct seeding is a potentially viable alternative to transplanting for basil stand establishment, there is a need to identify a tractor-drawn seeder that can plant basil at the required shallow depth. In the interim, large-scale producers of basil should continue to use transplants to obtain reliable stand establishment.

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