Preharvest Factors Influencing Postharvest Quality of Tropical and Subtropical Fruit
Climate/environment Rootstock/scion Planting design Pruning practices Pest management Irrigation Plant growth regulators Plant nutrition The goal for postharvest physiologists, whether they are work in basic or applied research, is to maximize the postharvest quali horticultural commodities. Quality relates to several factors that ca commodity specific and mean different things to different people. T consumer may perceive quality as it relates to appearance, flavor dollar value. The packinghouse handler, wholesale distributor, retailer, in contrast, may perceive quality as ease of handling, un mity of packaging, and freedom from physical and physiologi defects as well as pathological breakdown. Although there is muc learn about the mechanisms of a given tropical or subtropical fru response to the postharvest environment, past research has pro handlers with the general principles of sound commodity mana ment. These principles include temperature, relative humidity, at sphere modification, cooling, and judicious use of fungicides a waxes following harvest. These management strategies are of cr importance for tropical products given their long transit conditions a the potential need for postharvest insect disinfestation quaran treatments. This paper will examine the role of the preharvest environment how it may affect the postharvest life of tropical and subtropical fr Essentially, preharvest factors can influence both the rate of development and maturation. The preharvest environment can have a physical impact on fruit quality: for example, wind or ins scarring may reduce the packout percentage. Finally and most im tant, but much more difficult to quantify, are those effects t influence susceptibility to physiological and pathological breakdow This review will not dwell on the latter, but recognizes that t influence of preharvest factors on postharvest decay incidence severity has been well documented. One must remember that the plant exists in a dynamic environm and therefore can respond to changes to that environment i interactive fashion. The factors listed in Table 1 are neither inclusive nor mutually exclusive. Several examples will illustrate interaction between one or more preharvest factors on postharves quality.
Factors affecting mesocarp discolouration severity in 'Pinkerton' avocados (Persea americana MILL.)
The susceptibility of the 'Pinkerton' avocado cultivar to mesocarp discolouration, after storage, has seriously threatened its export from South Africa. This disorder has proven to be complex, requiring a better understanding of the fruit's physiology. The purposes of this study were to identify the role of preand postharvest factors, or their interactions, in the development of the problem. This was done by obtaining fruit from several production areas of varying mesocarp discolouration histories (referred to as "high", "medium" or "Iow risk" areas) during the 2000 and 2001 seasons. Fruit were stored at 8,5.5 and 2°C for 30 days, as well as ambient (20°C). Evaluations of fruit quality were made before and after storage, as well as after softening. Once removed from storage the weight loss (during storage) was determined, and fruit firmness and carbon dioxide (C02) production rates monitored daily. It was found that temperatures below the recommended shipping temperature of 5.5°C, Le. 2°C, produced the best internal fruit quality. This was supported by the membrane integrity studies that showed less membrane stability at the warmer storage temperature of 8°C. Furthermore, remained hard during storage and subsequently had an extended shelf life. Fruit origin was also found to play a major role in browning potential, with discolouration being consistently more severe in fruit from "high risk" areas and increasing in severity as the season progressed. The rate of CO2 production was found to follow a similar trend, with rates increasing as the season progressed, and also being slightly higher in fruit from "high risk" areas. The higher CO2 production rates were thought to be related to a decrease in membrane integrity as the season progressed. While storage temperature was not found to have a significant effect on the rate of CO2 production after storage, it did affect the time taken to reach the maximum rate, with fruit stored at 2°C taking longer. Biochemical analyses to determine the concentration of total phenolics and the activity of the enzyme polyphenol oXidase (PPO) also showed that the potential for browning was initiated by preharvest conditions. While no significant differences were found between growers with regards to total phenol concentrations, the PPO activity was found to be higher in fruit from poor quality areas, and subsequently browning potential was expected to be higher in these fruit. It was, however, found that the potential for browning could be reduced by storing fruit at 2°C, as this decreased the total phenolics concentration. This evidence further emphasized the idea that storage at 2°C could be highly advantageous.
Water Quality Aspects of Irrigation and Drainage: Past History and Future Challenges for Civil Engineers
This paper presents a brief history of irrigation and drainage related to ASCE activities on its Jubilee. This paper discusses legislation and policies that affect irrigation and drainage practices, water quality constituents of increasing concern in irrigation and drainage practices, and presents a prognosis on the future of declining freshwater resources available for irrigated agriculture and growing water quality problems in irrigation and drainage. Civil engineers in ASCE’s Irrigation and Drainage Division have compiled an 80-year history of highly meritorious service and accomplishments. In the next millennium, civil engineers will face a formidable challenge in managing and protecting the precious freshwater resources in the U.S.