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- Author or Editor: Carlos H. Crisosto x
Efficacy of controlled atmosphere (CA) conditions for decay control in 'Thompson Seedless' table grapes was evaluated during the 1998-2000 seasons. During the 1998 season, early (16.5% soluble solids concentration = SSC) and late harvested (19% SSC) grapes were exposed to 5%, 10%, 15%, 20%, or 25% CO2 combined with 3%, 6%, and 12% O2. In 1999 and 2000, 10% or 15% CO2 combined with 3%, 6%, or 12% O2 were used. In all trials, fruit were initially SO2 fumigated and air-stored grapes were used as controls. Storage atmospheres did not affect SSC, titratable acidity (TA), or sugar-to-acid ratio (SSC: TA). The main storage limitations for early harvested 'Thompson Seedless' table grapes were “off flavor” and rachis and berry browning development, which resulted from exposure to >10% CO2. However, ≥15% CO2 was needed to control total decay and nesting development independent of O2 concentrations. High carbon dioxide atmospheres (15% to 25%) were more effective in decay control without detrimental effects on quality when late harvested grapes were used. The combination of 15% CO2 with 3%, 6%, or 12% O2 is suggested for up to 3 months storage only for late harvested 'Thompson Seedless' table grapes; it should not be used for early harvested grapes.
The relationship of phenolic composition and polyphenoloxidase activity (PPO, E.C. 1.14.18.1) to browning potential (BP) was studied in buffer extracts of peach [Prunus persica L. Batsch) and nectarine [P. persica var. nectarine (L.) Batsch] fruit skin. The BP varied among cultivars with `Flavorcrest' having the highest value and `Maycrest' the lowest. On average, over 83 % of the browning measured at the end of the S-hour incubation occurred during the first hour. The total soluble phenolics (TSP), the total anthocyanin (TA), and glutathione content (GLU) varied among cultivars, but were not significantly correlated to the BP. Of the phenolics determined by HPLC, only chlorogenic acid had a significant positive correlation and epicatechin a significant negative correlation with BP by the first hour of incubation. The PPO activity, ranging from 4 to 11 optical density units per gram dry weight per minute among peaches and nectarines, was not significantly correlated with BP. However, no browning was detected if the buffer extract was previously boiled. These results indicated that browning in the buffer extracts of peach and nectarine skin tissue depends on the presence of PPO activity and chlorogenic acid, which are major contributors to enzymatic browning.
The formation of metallo-pigmentation and copigmentation as potential mechanisms of inking formation was investigated in peach and nectarine skin tissues. Cyanidin-3-glucoside, the most abundant anthocyanin in peaches and nectarines, formed very purple ferric complexes with an anthocyanin/iron molar ratio of two. Greenish metallo complexes between ferric ion and chlorogenic acid, caffeic acid, catechin, or epicatechin formed with an phenolic/iron molar ratio of one. The lack of copigmentation pointed out the importance to focus research on the metallo-phenolics reaction. High intensity of dark color formation was developed with cyanidin-3-glucoside, followed by caffeic acid, chlorogenic acid, catechin, and epicatechin on an equal molar basis. Citric acid acted as a strong iron chelator to prevent and reverse the formation of ferric cyanidin-3-glucoside complexes. The variety of dark and light colored spots observed on the surface of peaches and nectarines is explained by the formation of metallo-pigment complexes.
Dark skin discoloration development on peach and nectarine cultivars was investigated in response to exogenous pH and metallic ions. The influence of skin abrasion and washing in combination with exogenous contaminants was studied in a factorial design experiment by using skin discs. Only abraded skin discs with and without washing developed discoloration after being exposed to high pH and different metallic ion concentrations. Among the metallic ion contaminants studied (Fe, Al, Cu, Sn, Zn, and Na), iron was the most effective in causing dark skin discoloration at physiological pH (3.5). Iron concentrations ≥10 ppm induced dark discoloration on abraded fruit skin. Dark discoloration development produced by exposing the skin tissue to pH levels >6 was reversible, whereas the dark discoloration induced by iron and aluminum remained stable.
Cultivar segregation according to their organoleptic perception was attempted by using trained panel data evaluated by principal component analysis in four sources of 24 peach and 27 nectarine cultivars as a part of our program to develop minimum quality indexes. Source significantly affected cultivar ripe soluble solids concentration (RSSC) and ripe titratable acidity (RTA), but it did not significantly affect sensory perception of flavor, sourness and aroma by the trained panel. On two out of 51 cultivars tested, source played a role on sweetness perception. In all of these cases, when source fell out of the proposed cultivar organoleptic group it could be explained by fruit being harvested outside the commercial physiological maturity (immature or overmature). The perception of the four sensory attributes was reduced to three principal components that explain 92% for peach and 94% for nectarine of the variation in the sensory characteristics of the cultivars tested. Season did not affect significantly the classification of three cultivars that were evaluated during these two seasons. By plotting organoleptic characteristics in PC1 and PC2 (∼76%), cultivars were segregated into groups (balanced, robust, sweet, peach or nectarine aroma, and/or peach or nectarine flavor) with similar sensory attributes; nectarines were classified into five groups and peaches into four groups. Based on this information, we recommend that cultivars should be clustered in organoleptic groups and a development of a minimum quality index should be attempted within each organoleptic group rather than proposing a generic minimum quality index based on RSSC. This organoleptic cultivar classification will help to match ethnic preferences and enhance the current promotion and marketing programs.
The effect of two fruit maturity stages on the quality attributes of four fresh fig cultivars was examined, including consumer acceptance and antioxidant capacity. Fig quality attributes such as weight, soluble solids concentration (SSC), titratable acidity (TA), SSC:TA, firmness, antioxidant capacity, and consumer acceptance varied by cultivar. Fig cultivars harvested at the advanced maturity stage (“tree ripe”) had lower TA and firmness but higher weight, SSC, and SSC:TA than figs harvested at “commercial maturity.” Fig maturity did not affect antioxidant capacity, but tree ripe figs had higher consumer acceptance than commercial maturity figs. SSC was more highly correlated with consumer acceptance than TA or SSC:TA, but other factors may also be important in controlling this relationship. Cultivars with high SSC and firmness, at a maturity stage high enough to tolerate harvesting and postharvest handling, should be selected to develop the fresh fig industry. Because fig firmness is a concern, changes to packaging should be evaluated to protect the flavor of advanced maturity figs during postharvest handling.
`Snow King' peaches (Prunus persica) harvested at commercial maturity were subjected to different carbon dioxide (CO2) and oxygen (O2) atmosphere combinations for a 2-week simulated transportation [0 °C (32 °F)] period after 1 week of cold storage in air (0 °C). In 1998, air or 5%, 10%, 15%, or 20% CO2 combined with 3% or 6% O2 were used during shipment. The trial was repeated in 1999, but for this year half of the fruit were treated with a 50 mg·L-1 (ppm) aminoethoxyvinylglycine (AVG) postharvest dip before storage and simulated shipment. In addition, O2 levels during simulated shipment were reduced to 1.5% and 3%. At harvest and after the 2-week simulated shipment, fruit flesh firmness, soluble solids concentration (SSC), titratable acidity (TA), and chilling injury (CI) were evaluated. For both years, there were no significant differences in quality attributes among the different treatments after the simulated shipment period. SSC and TA did not change during 5 days postshipment ripening at 20 °C (68 °F). In 1998 all treatments softened rapidly during the postshipment ripening at 20 °C, and were ready to eat [13 N (1 N = 0.225 lb force)] after 3 days. In 1999, both the high CO2 atmospheres during shipment and the AVG postharvest dip slowed the rate of softening during subsequent ripening at 20 °C. With respect to fruit softening, there was significant interaction between storage atmosphere and AVG treatment. AVG-treated fruit shipped under a 20% CO2 + 3% O2 atmosphere did not soften to the transfer point (firmness = 27 N) within our 5-day ripening period, while fruit not treated with AVG and shipped under the same atmosphere softened to the transfer point in 3 days. Control fruit (no AVG + air shipment) softened to the transfer point in 2 days. Our previous work found that when white flesh peaches soften to less than 27 N firmness they become very susceptible to impact bruise injury during retail distribution. We call this critical level of fruit flesh firmness the transfer point. Symptoms of CI, low O2, or high CO2 injury were not observed in any treatment in either year.
The susceptibility to chilling injury (CI) or internal breakdown (IB) was evaluated in the most currently planted yellow- and white-flesh peach [Prunus persica (L.) Batsch] and nectarine [Prunus persica var. nectarine (L.) Batsch] and plum [Prunus salicina Lindel] cultivars from different breeding sources and fruit types. Cultivars were segregated into three categories (Cat. A, B, and C) according to their susceptibility to CI or IB symptoms (mealiness and flesh browning) when exposed to 0 °C or 5 °C storage temperatures. Cultivars in Cat. A did not develop any symptoms of CI after 5 weeks of storage at either temperature. Cultivars in Cat. B developed symptoms only when stored at 5 °C within 5 weeks of storage. Cultivars were classified in Cat. C when fruit developed CI symptoms at both storage temperatures within 5 weeks of storage. Most of the yellow- and white-flesh peach cultivars developed IB symptoms when stored at both storage temperatures (Cat. C). Most of the new nectarine cultivar introductions did not develop CI symptoms when stored at 0 °C or 5 °C after 5 weeks (Cat. A). Three out of six plum cultivars tested had CI symptoms within 5 weeks storage at 0 °C. However, all of the plum cultivars tested developed CI symptoms when stored at 5 °C (Cat. B). The importance of proper temperature management during postharvest handling was demonstrated.
Reduced doses of sulfur dioxide (SO2) were evaluated for the fumigation of marine containers with respect to the concentration × time (CT) product and gas penetration. Two commercial export containers were loaded at 32 °F (0 °C) with 20 metric pallets [40 × 48 inches (102.5 × 123.1 cm)] comprised of 72 expanded polystyrene foam boxes (12 tiers, 6 boxes/tier) of table grapes (Vitis vinifera) and fumigated with 1.0 and 0.5 lb (0.454 and 0.227 kg) SO2, respectively. A third marine container was loaded with 20 metric pallets comprised of 84 plastic boxes of table grapes (14 tiers, 6 boxes/tier) and fumigated with 0.25 lb (0.113 kg) SO2. The boxes contained 16 lb (7.3 kg) of table grapes distributed in nine polyethylene cluster bagsenclosed in a perforated polyethylene box liner. Fumigations were performed through the bottom seal of the rear door from pre-weighed compressed SO2 cylinders. CT product was calculated after taking samples of the atmosphere in the container every 5 to 10 min and measuring the ambient SO2 concentration with a gas sampling pump and colorimetric dosimeter tubes. Pallet and box penetration of the gas was assessed by placing passive colorimetric SO2 dosimeters inside the cluster bags in boxes located in both the third and ninth center boxes from the top of pallets located in the front, center, and rear of the load. Fumigations with 1.0, 0.5, and 0.25 lb SO2, with calculated CT products at 32 °F of 925, 360, and 40 ppm-h (μL·L-1·h-1) respectively, were found to provide excessive, adequate, and insufficient SO2 doses.
Studies on the influences of “orchard factors” such as cultivar, harvest time, crop load, fruit canopy position, irrigation, and nitrogen regimes were investigated for plums, nectarines, and peaches at the Kearney Agricultural Center (San Joaquin Valley, Calif.a). These preharvest factors affected internal browning and mealiness incidence differently. More-reliable benefits of treatments to eliminate or reduce internal breakdown may be accomplished by using outer canopy fruit. Optimum quality expression and subsequent consumer satisfaction for each cultivar can be achieved by understanding the role of preharvest factors and harvest time on fruit quality and potential postharvest life.