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Julio Loaiza and Marita Cantwell

Respiration rates of freshly harvested cilantro were moderately high (CO2 at 15 to 20 μL·g-1·h-1) and ethylene production rates were low (<0.2 nL·g-1·h-1) at 5 °C and were typical of green leafy tissues. Cilantro stored in darkness at a range of temperatures in air or controlled atmospheres was evaluated periodically for visual quality, decay, aroma, off-odor, color, and chlorophyll content. Cilantro stored in air at 0 °C had good visual quality for 18 to 22 days, while at 5 and 7.5 °C good quality was maintained for about 14 and 7 days, respectively. An atmosphere of air plus 5% or 9% CO2 extended the shelf-life of cilantro stored at 7.5 °C to about 14 days. Quality of cilantro stored in 3% O2plus CO2 was similar to that stored in air plus CO2. Atmospheres enriched with 9% to 10% CO2 caused dark lesions after 18 days; 20% CO2 caused severe injury after 7 days. Although visual quality could be maintained for up to 22 days, typical cilantro aroma decreased notably after 14 days, regardless of storage conditions.

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Augusto Trejo-Gonzalez and Marita Cantwell

A lime solution is an efficient starch gelatinization agent during the traditional process of nixtamalization of corn for tortilla production. Although the saturated Ca(OH)2 solution is usually heated to speed the process, similar physical-chemical changes occur to corn steeped at room temperature. In addition, the steeped grains are capable of rapid germination. In this study we explored whether, in barley grains subjected to the same steeping conditions, there would be an acceleration of biochemical changes for the production of malt. Barley grains cv. Esmeralda six-row were steeped in saturated solutions of lime from 0% to 2% (w/w) at 18 to 23 °C for up to 72 hours. After treatment, the grains were washed with water and placed in a germination cabinet at 20 ± 2 °C and 90% RH for up to 96 hours to germinate. Activity of α-amylase (U/mg protein), sprout length (cm), seed viability (tetrazolium test), and respiration rates were determined. Scanning electron micrographs were prepared. There was a very rapid uptake of lime solution by the barley grains during the first 30 hours of treatment. The barley grains were 98% viable after all periods of steeping. Grains steeped 24 hours and germinated 70 hours had the highest activity of α-amylase, longest sprout length and highest percentage of germination. Under SEM, chemical gelatinization of starch grains was observed in barley sections after different steeping treatments, and starch breakdown was observed in grains during germination. No fungal growth was observed during germination after the steeping treatments. These results demonstrate that steeping in lime solutions could shorten the period required for barley germination and similar conditions may be useful for germination of other cereal and vegetable seeds.

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Rawia El-Bassuoni and Marita Cantwell

Bell pepper fruits (green and red) were stored intact or prepared in dices (1 × 1 cm), washed with chlorinated water, biot dried, and stored in air or controlled atmospheres (air or 3% O2 with 0, 5 or 10% CO2) at 0, 5 or 10C for up to 20 days. Dicing resulted in respiration rates 2-3 times higher than those of intact peppers, but did not result in measureable increases in ethylene production. Samples were periodically transferred to 15C for 12 h before evaluation for visual quality, decay, discoloration, aroma, flavor, texture, and sugar content. Quality changes were similar for green and red fruit of the same cultivar. Intact peppers are chilling sensitive, but the quality of diced peppers was maintained best at 0C. The shelf-life of diced pepper at 10 and 5C was 1/2 to 2/3 that of intact peppers. Atmospheres containing 5 or 10% CO2 reduced decay and increased the shelf-life of diced peppers, but were not as effective as storage in air at 0C. Storage at 0C also resulted in greater retention of sugars than storage under other conditions. High CO2 atmospheres resulted in softening of pepper tissue and increased electrolyte leakage. Aroma and flavor scores declined more rapidly in CA than in air storage.

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Luis Hernández-Rivera, Robert Mullen and Marita Cantwell

Asparagus (Asparagus officinalis L.) spears (cv. UC 157) trimmed to 20 cm were cooled 0, 4, 8, 12, 16, and 20 hours after harvest and evaluated for resistance to shear at 5 and 10 cm above the cut end immediately after cooling and during storage at 0.5, 2.5, and 5C. Resistance to shear increased during cooling delays and with time in storage. Initial cooling delays and simulated marketing conditions (transfer to 15C for 1 day) were the principal causes of increased resistance to shear. A 4-hour cooling delay resulted in an average 40% increase in resistance to shear. Transfer to 15C for 1 day resulted in a greater increase in shear force in the rapidly cooled than in the delayed-cooled spears. Increases in resistance to shear during storage varied from 0% to 50% and depended on the storage temperature, time, and the initial cooling delay. Spears trimmed to a green base showed less increase in shear force after storage than did spears trimmed to a white base. The visual quality of asparagus stored for 14 days was similar (excellent) among spears from different storage temperatures and between green- and white-base spears. Storage quality after 24 days had decreased more in spears stored at 5C than at 2.5 or 0.5C, and more in the green-base than the white-base spears.

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Ma. Teresa MartÌnez-Damian and Marita I. Cantwell

Spinach is not packed commercially in modified-atmosphere packaging due to difficulties in maintaining beneficial conditions during distribution, where temperature fluctuations can occur. However, low O2 and high CO2 atmospheres can be useful to retard yellowing and deterioration. In two experiments we studied developing and full-size leaves stored at 7.5 °C in air and controlled atmospheres of 0.5% O2 + 10%CO2 and 5%O2 + 10% or 20% CO2. Subjective quality evaluations (visual quality, decay, discoloration, off-odors, and yellowing) and objective evaluations (L*a*b* color values, chlorophyll, pH and titratable acidity, ammonia, and ethanol and acetaldehyde) were conducted every 3 days during 15 days. The developing leaves had higher visual quality and lower off-odor scores during storage than did the full-size leaves. In air storage, leaves were below the limit of salability by day 12. The atmospheres containing 10% CO2 were similarly effective in maintaining the visual quality and greenness of the leaves, and reduced off-odors in developing but not full-size leaves. The 20% CO2 atmosphere resulted in some leaf damage. Ammonia concentrations increased during storage, with lowest and highest concentrations in leaves stored in air and 20% CO2, respectively. Tissue pH only slightly increased from 6.5 in air-stored samples, but increased notably during storage in the controlled atmospheres. At 2.5 and 7.5 °C, a plastic film providing a 5% O2 and 6% CO2 atmosphere resulted in better quality spinach than that obtained with either a 10% O2 and 3% CO2 package atmosphere or the commercial perforated polybag.

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Andrés F. López Camelo and Marita Cantwell

A study on quality changes of fresh-cut onions under different temperatures and handling conditions was conducted. High-quality onions were peeled and diced into 1 x 1 cm pieces. Replicated (3) experimental units (150 g) were stored for 20 days in glass jars in a humidified air flow under the following conditions: 0, 5, and 10 °C. To simulate rough handling, onion pieces were rolled with a rolling pin with enough pressure to induce some damage and stored at 5 °C. Objective (color, soluble solids, and dry and fresh weights) and subjective (visual quality, decay, aroma, and discoloration) measurements were taken every 5 days. Fresh and dry weights as well as soluble solid content decrease with storage time and temperature, but decay and development of off-odors increased. An overall browning was observed at the higher temperatures. Colorimeter readings indicate that b* and chroma increased with storage and temperature, while a* values decreased. No definite trends were observed in L* values, and no major differences were found in the hue, although hue tend to be higher with lower temperatures. Rough handling resulted in a faster quality deterioration rate in comparison with pieces stored at the same temperature. At 0 °C, diced onions could be stored satisfactorily for 20 days, although some quality changes took place. At 5 °C visual quality may be acceptable after 10 days of storage, but discoloration started to show up after 5 days, reducing acceptability. Storage at 10 °C only is possible for very short periods of time. Rough handling increases the rate of quality deterioration.

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Silvina I. Portela and Marita I. Cantwell

Although minimal processing increases the perishability of products, largely due to microbial decay, quality changes may be similar between tissues from intact produce and fresh-cut pieces. This study compared pulp quality changes of intact cantaloupe melons and of sanitized fresh-cut pieces (1.8 x 3-cm cylinders) during storage in air at 2.5 (cv. Corona) and 5 °C (cv. Corona and Durango) for 15 days. Quality evaluations included subjective (visual quality, decay, translucency, aroma, off-odor) and objective (color, firmness, SSC) measurements. At 5 °C, visual quality of the pieces was below the limit of salability by day 15 due to decay, whereas pulp from stored melons was excellent. Pulp from intact melons did not suffer from development of translucency as did the fresh-cut pieces. At 5 °C, pulp from intact fruit had higher aroma scores than pieces, but there were no differences in off-odor scores. At 2.5 °C there were no differences in the subjective quality measurements of pulp from intact or fresh-cut pieces. Pulp from intact fruit had higher chroma (at 2.5 and 5 °C) and L* (only at 5 °C) than the pieces after 6 or 15 days, depending on the variety. There were no differences in hue between intact and fresh-cut pulp. Pulp from intact and fresh-cut pieces had similar firmness changes and SSC during storage at 2.5 and 5 °C. We conclude that pulp of intact fruit and fresh-cut pieces had similar quality up to 15 days at 2.5°C; but at 5 °C, the fresh-cut pieces lost intrinsic quality (visual quality, aroma, and color) before the pulp of intact fruit did.

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Maria Dolores Muy-Rangel and Marita Cantwell

Temperature management of fresh products begins with proper handling at harvest. Inadvertent abuses, such as lengthy delays to cool or exposure of harvested product to the sun, can detrimentally impact postharvest quality. We used mature-green bell peppers to determine the periods of sun exposure (midday during August in Davis, Calif.) necessary to affect quality attributes (visual appearance, gloss, weight loss, and firmness). Peppers were evaluated after cooling, storage at 7.5 °C for 3 or 7 days, and storage plus 2 days at 20 °C. The impacts of sun exposure, although sometimes barely detectable after cooling, became more noticeable once the peppers were stored. The additional transfer period to 20 °C after storage further accentuated the impact of the exposure. Depending on the experiment, sun-exposed areas reached 45 to 55 °C within 1 hour. Peppers typically lost 0.4% to 0.5% and 1.0% to 1.3% weight during 1- and 2-hour exposures, respectively. Changes in gloss and firmness (whole fruit compression and pulp penetration) were preceded by changes in visual appearance. Exposure to the sun for 0.5 hour did not impact postharvest quality of peppers. Exposures from 1 to 1.5 hours usually resulted in changes apparent only after the storage period. Such exposures are problematic in commercial situations because these peppers are unlikely to be eliminated during sorting on the packingline. Exposures of 1.5 to 2 hours usually resulted in an immediate change in appearance (pitting, blistering, color change).

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Marita Cantwell, Gyunghoon Hong and Ron Voss

A USDA germplasm collection of garlic (Alliumsativum) and related species (A. ophioscorodon, A. longicuspis) has been evaluated for horticultural characteristics and composition under California production conditions for several years. In 2004, 198 of the 217 accessions in the collection were evaluated. Bulbs were manually harvested late June to early July, cured about 3 weeks shaded at ambient temperatures, and the outer whorl of cloves manually peeled. Bulb and clove weights and percentage of dry matter were determined. Freeze-dried garlic powder was analyzed for alliin (precursor of flavor and health compounds) concentrations by HPLC. Thiosulfinates (mostly allicin, responsible for flavor and pungency) were determined by a spectrophotometric assay. Among the accessions evaluated in 2004, the percentage of dry matter ranged from 32.8% to 44.9%. Alliin content varied from 8.9 to 29.7 mg·g-1, and thiosulfinate concentrations ranged from 32.7 to 114.0 μmol·g-1. For comparison, the widely grown varieties California Early and California Late averaged 39.5% and 40.8% dry matter, 18.6 and 20.6 mg·g-1 alliin, and 68.1 and 78.8 μm·g-1 thiosulfinates.

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Francine Dickie, Ron Voss*, Gyunghoon Hong and Marita Cantwell

Red and white skin potatoes (`Cal Red', `Cal White', `Durango', VC1015, `Yukon Gold', `Latona', A94381, and `Satina') were harvested from plots in commercial fields in Kern and San Joaquin Counties and at the Univ. California Research Center at Tulelake. After washing and sorting, potatoes were held in plastic trays in the dark (black plastic bags) or exposed to light (90 cm below cool-white fluorescent GE Watt-Miser 34W bulbs, ≈1300 lux) at 20 °C. After 0, 3, 6 and 9 days, potatoes were scored for appearance of greening (1 to 5 scale), evaluated for external color (L*a*b* color values), skin chlorophyll concentration, and glycoalkaloid concentrations. For the latter, freeze-dried slices of tuber were extracted and analyzed by colorimetry and HPLC for alpha-solanine and alpha-chaconine. Initial glycoalkaloid concentrations varied among cultivars, with `Cal Red' consistently having the highest concentrations. Tubers stored in the dark had no or a slight increase in glycoalkaloid concentrations. Light exposure resulted in increased glycoalkaloid concentrations in all cultivars, but to varying degrees. Some varieties had negligible changes while others increased as much as eightfold. The average increase was 300%. Generally, `Cal White' had the largest light-induced increases in glycoalkaloids.