Carlos H. Crisosto

Effects of continuous 0.3 ppm ozone exposure on decay development and physiological responses of peaches and table grapes in cold storage

Continuous ozone exposure at 0.3 ppm (v/v) (US-OSHA Threshold Limit Value for short term exposure) inhibited aerial mycelial growth and sporulation on ‘Elegant Lady’ peaches wound inoculated with Monilinia fructicola, Botrytis cinerea, Mucor piriformis ,o rPenicillium expansum and stored for 4 weeks at 5 °C and 90% relative humidity (RH). Aerial growth and sporulation, however, resumed afterward in ambient atmospheres. Ozone exposure did not significantly reduce the incidence and severity of decay caused by these fungi with the exception of brown rot. Gray mold nesting among ‘Thompson Seedless’ table grapes was completely inhibited under 0.3 ppm ozone when fruit were stored for 7 weeks at 5 °C. Gray mold incidence, however, was not significantly reduced in spray inoculated fruit. Continuous ozone exposure at 0.3 ppm increased water loss after 5 weeks of storage at 5 °C and 90% RH in ‘Zee Lady’ peaches but not after 4 weeks of storage in ‘Flame Seedless’ grapes. Respiration and ethylene production rates of ‘O’Henry’ peaches were not affected by previous exposure to 0.3 ppm ozone. In every test, no phytotoxic injuries of fruit tissues were observed in ozonated or ambient atmosphere treatments.

Carbon dioxide-enriched atmospheres during cold storage limit losses from Botrytis but accelerate rachis browning of 'Redglobe' table grapes

We evaluated a range of CO2 and O2 concentrations as a potential substitute to SO2 treatments for controlling decay development on ‘Redglobe’ table grape during storage. During the 1998 season, early (14% soluble solids concentration, SSC) and late harvested (17% SSC) ‘Redglobe’ grapes were stored in 16 controlled atmospheres of 5, 10, 15, 20, and 25 kPa CO2 combined with 3, 6, and 12 kPa O2. During the 1999 season, 10 or 15 kPa CO2 combined with 3, 6, and 12 kPa O2 were tested in comparison with air stored grapes as control. In the 2000 season, late harvested ‘Redglobe’ grapes were kept in 12 kPa CO2+ 6k Pa O 2 in comparison with standard commercial storage practices of SO2 fumigation. None of the atmospheres tested for up to 12 weeks at 0 °C influenced SSC, titratable acidity (TA), SSC:TA, or berry shatter and browning. Rachis browning was accelerated and trained judges perceived ‘off-flavor’ in grapes exposed to CO2 levels above 10 and 15 kPa for early and late harvested ‘Redglobe’ grapes, respectively. Atmospheres including above 10 kPa CO2 controlled decay incidence and spread among berries (nesting) independent of O2 concentrations during storage at 1 °C for up to 8 weeks and after 3 days at 20 °C, simulating a retail display period. Based on these data, a combination of 10 kPa CO2 with 3, 6 or 12 kPa O2 is suggested for up to 12 weeks storage for late harvested ‘Redglobe’ grapes. An atmosphere of 10 kPa CO2+ 6k Pa O 2 is suggested for early harvested ‘Redglobe’ grapes, but not to exceed 4 weeks.

Endopolygalacturonase: a Candidate Gene for Freestone and Melting Fleshin Peach

Peach fruit are handled, processed, and marketed according to their stone adhesion and fruit softening type. Uncertainty exists over whether these simply inherited traits are controlled by two linked loci, Freestone (F) and Melting flesh (M) or one multi-allelic locus, and whether M is controlled by the cell wall degrading enzyme, endopolygalacturonase. From morphological and molecular analysis of two related segregating populations of peach, we conclude that a single locus containing at least one gene for endopolygalacturonase, controls both F and M with at least three effective alleles. A simple diagnostic PCR test is now available for the three major phenotypes of freestone melting flesh (FMF), clingstone melting flesh (CMF), and clingstone non-melting flesh (CNMF).

Effect of Gaseous Ozone Exposure on the Development of Green and Blue Molds on Cold Stored Citrus Fruit

The effects of gaseous ozone exposure on in vitro growth of Penicillium digitatum and Penicillium italicum and development of postharvest green and blue molds on artificially inoculated citrus fruit were evaluated. Valencia oranges were continuously exposed to 0.3 ± 0.05 ppm(vol/vol) ozone at 5°C for 4 weeks. Eureka lemons were exposed to an intermittent day-night ozone cycle (0.3 ± 0.01 ppm ozone only at night) in a commercial cold storage room at 4.5°C for 9 weeks. Both oranges and lemons were continuously exposed to 1.0 ± 0.05 ppm ozone at 10°C in an export container for 2 weeks. Exposure to ozone did not reduce final incidence of green or blue mold, although incidence of both diseases was delayed about 1 week and infections developed more slowly under ozone. Sporulation was prevented or reduced by gaseous ozone without noticeable ozone phytotoxicity to the fruit. A synergistic effect between ozone exposure and low temperature was observed for prevention of sporulation. The proliferation of spores of fungicide-resistant strains of these pathogens, which often develop during storage, may be delayed, presumably prolonging the useful life of postharvest fungicides. In vitro radial growth of P. italicum, but not of P. digitatum, during a 5-day incubation period at 20°C was significantly reduced by a previous 0.3 ± 0.05 ppm ozone exposure at 5°C for 4 days. Inoculum density did not influence the effect of gaseous ozone on decay incidence or severity on oranges exposed to 0.3 ± 0.05 ppm ozone at 20°C for 1 week. Susceptibility of oranges to decay was not affected by a previous continuous exposure to 0.3 ± 0.05 ppm ozone at 20°C for 1 week. A corona discharge ozone generator was effective in abating ethylene in an empty export container.

Understanding consumer acceptance of early harvested 'Hayward' kiwifruit

During two seasons, ‘in-store’ consumer acceptance tests were performed to determine the relationship between ripe soluble solids concentration (RSSC) and/or ripe titratable acidity (RTA) on ‘Hayward’ kiwifruit consumer acceptance. For this, 252 consumers were presented kiwifruit slice samples with RSSC of 11.0, 12.0, 13.0, and 14.0% with a RTA ranging from 0.8 to 1.2%. Kiwifruit with RSSC that ranged from 11.6 to 13.5% were always liked by consumers but with different degrees of liking. A 12.5% RSSC is proposed as a minimum quality index for early-marketed kiwifruit. RTA played a significant role in consumer acceptance only on kiwifruit that had RSSC11.6% with RTA1.17% (‘sour’). This kiwifruit quality survey indicated that some vineyards had kiwifruit with RSSC higher than 12.5% before they met the recommended minimum maturity standard of 6.5% HSSC. Kiwifruit picked with SSC6.2% developed flesh breakdown. This work demonstrated that some California vineyards could produce high taste quality (12.5% RSSC) kiwifruit before they reach 6.5% SSC measured when kiwifruit are hanging on the vines.

Development of ChillPeach genomic tools and identification of cold-responsive genes in peach fruit

The ChillPeach database was developed to facilitate identification of genes controlling chilling injury (CI), a global-scale post-harvest physiological disorder in peach. It contained 7,862 high-quality ESTs (comprising 4,468 unigenes) obtained from mesocarp tissues of two full-sib progeny contrasting for CI, about 48 and 13% of which are unique to Prunus and Arabidopsis, respectively. All ESTs are in the Gateway® vector to facilitate functional assessment of the genes. The data set contained several putative SNPs and 184 unigenes with high quality SSRs, of which 42% were novel to Prunus. Microarray slides containing 4,261 ChillPeach unigenes were printed and used in a pilot experiment to identify differentially expressed genes in cold-treated compared to control mesocarp tissues, and in vegetative compared to mesocarp tissues. Quantitative RT-PCR (qRT-PCR) confirmed microarray results for all 13 genes tested. The microarray and qRT-PCR analyses indicated that ChillPeach is rich in putative fruit-specific and novel cold-induced genes. A website (http://bioinfo.ibmcp.upv.es/genomics/ChillPeachDB) was created holding detailed information on the ChillPeach database.

Developing a quantitative method to evaluate peach (Prunus persica) flesh mealiness

A quantitative method to measure peach flesh mealiness based on free juice was developed. Free juice was measured by subjecting fruit tissue to a pressing force of 667 N for 1 min before centrifugation. After this extraction, the juice was collected and centrifuged at 6000g for 10 min. The supernatant was weighed and used to represent the free juice from the total initial tissue. The percentage of free juice was more sensitive and it had a higher correlation to mealiness measured visually and by a trained panel than the extractable juice method. Our work also demonstrated that trained judges were able to perceive mealiness earlier than visual mealiness symptoms were expressed. This free juice measurement provides an objective and accurate method to evaluate mealiness potential of stone fruit breeding lines and fruit biochemical and/or physiological changes during postharvest storage.

Effect of continuous exposure to exogenous ethylene during cold storage on postharvest decay development and quality attributes of stone fruits and table grapes

The influence of continuous exposure to exogenous ethylene on fruit quality and on the development of postharvest brown rot of stone fruits and gray mold of table grapes during long-term cold storage was investigated using selected cultivars of table grapes (nonclimacteric) and climacteric (peach, plum, nectarine, and apricot) and nonclimacteric (sweet cherry) stone fruits. Depending on the experiment, climacteric stone fruits were exposed to concentrations of ethylene of 0, 0.1, 1, 3, 10, or 100 m ll 1 during storage at 0, 5, or 10 8C for up to 28 days; sweet cherries were exposed to 0, 0.01, 0.1, or 1 m ll 1 ethylene during storage at 0 or 5 8C for 21 days; and table grapes were exposed to 0, 0.125, 0.25, 0.5, or 1 m ll 1 ethylene during storage at 0 or 5 8C for up to 60 days. Neither incidence nor severity of brown rot were affected by constant ethylene exposure on stone fruits wound-inoculated with Monilinia fructicola . Similarly, ethylene did not affect gray mold nesting ability on table grapes artificially inoculated with Botrytis cinerea . Furthermore, ethylene exposure neither influenced external quality attributes (skin color on peaches and cherries, skin pitting and stem browning on cherries, and rachis browning on table grapes) nor internal quality attributes (flesh firmness, soluble solids concentration, and titratable acidity on all fruit, and flesh color and internal breakdown on climacteric stone fruits). The only exceptions were flesh softening of apricots, which in every test was significantly enhanced by exogenous ethylene, and flesh mealiness in experiments with ‘Elegant Lady’ peaches, the appearance of which was delayed by ethylene exposure in one case. In conclusion, no general commercial benefit could be expected from actively removing ethylene from cold storage rooms or transport containers containing peaches, plums, nectarines, sweet cherries, or table grapes. # 2002 Elsevier Science B.V. All rights reserved.

Understanding American and Chinese consumer acceptance of 'Redglobe' table grapes

‘In-store’ consumer acceptance tests were performed on a group of 400 American consumers and 250 native Chinese consumers to determine the relationship between ripe soluble solids concentration (SSC) and titratable acidity (TA) on consumer acceptance of ‘Redglobe’ grapes for different ethnic groups. For this, a group of Caucasian, Hispanic and Chinese-American consumers and a group of native Chinese consumers tasted monadically four individual berry half samples at room temperature with SSC ranging from 10 to 20% and TA from 0.30 to 1.80%. Grapes with SSC 16.1% were accepted by 70% of the American consumers and 47% of the Chinese consumers. However, the percentage of consumers that disliked these grapes was the same ( 21) for both ethnic groups. The difference in the percentages of Chinese and American consumers accepting the grapes was due to the ‘neither like nor dislike’ category. Chinese consumers chose the ‘neither like nor dislike’ category in approximately 34% of the cases, while approximately only 7% of the American consumers chose it. Our data confirmed that ‘Redglobe’ consumer acceptance is highly related to SSC:TA ratio but within a given SSC and TA level. In contrast to American consumers, Chinese consumer acceptance was not related to SSC:TA ratio when TA 0.80%. Thus, our work indicates that high TA affects consumer acceptance in relation to SSC:TA ratio depending on ethnic background.

Nutritional Quality of fruits and vegetables

The nutritional value of fruits and vegetables depends on their composition, which shows a wide range of variation depending on the species, cultivar, and maturity stage. This chapter describes the general characteristics of the components of fruits and vegetables, related to their benefits as food sources. There are two types of acids, namely aliphatic (straight chain) and aromatic acids. The most abundant acids in fruits and vegetables are citric and malic (both aliphatic) acids. However, large amounts of tartaric acid occur in grapes. Malic acid is the major component in oranges and apples. The acid content of fruits and vegetables generally decreases during maturation. Aromatic organic acids occur in several fruits and vegetables, but in very low concentrations. Benzoic acid occurs in cranberries, quinic acid in bananas, and chlorogenic acid in potatoes. In general, vegetables are a richer source of minerals than fruits, but both vegetables and fruits are considered nutrient-dense foods in that they provide substantial amounts of micronutrients, such as minerals and vitamins, but relatively few calories. Minerals have both direct and indirect effects on human health. The direct effects of minerals focus on the consequences of their consumption on human nutrition, while the indirect effects refer to their incidence in fruit and vegetable quality and subsequent consumer acceptance. From a direct nutrition standpoint, potassium has the biggest presence in both fruits and vegetables, but nitrogen and calcium show major impacts on horticultural crop quality.