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.
The role of fruit mineral composition on fruit softness and mesocarp discolouration in ‘Pinkerton’ avocado (Persea americana Mill.)
Summary The successful marketing and export of fruit depends, to a large degree, on the predictability and consistency of quality. The ‘Pinkerton’ avocado, however, is prone to a physiological disorder known as “mesocarp discolouration” during and after storage. Furthermore, fruit have been found to arrive at their European destination with variable softness. Mesocarp discolouration was initially thought to be the result of chilling injury, however differences in quality were noted between fruit from different origins. Fruit were subjected to mineral analysis following a suspicion that pre-harvest factors played a role in fruit quality. Excessive nitrogen concentrations were found to have the most significant role in determining the severity of mesocarp discolouration. In addition, decreasing copper, manganese and boron concentrations during the season also appeared to contribute to the development of the disorder. The results of this study indicate that interactions between minerals could be more important in determining quality than evaluating individual elements.
Modelling of Mooney viscosity relaxation in natural rubber
Abstract Better assessment of natural rubber (NR) quality and processability, through the identification of new attributes, is still a major challenge. With this scope, 12 model samples of natural polyisoprene and two of synthetic polyisoprene were characterized in terms of Mooney torque relaxation, using the standardized ISO289 method (ML(1+4)100, explained later in the Section 1 ). The main purpose of this study was to identify a model that gave a better fit for the experimental decay of Mooney torque over time (ML(t)=f(t)) than the usual power law model used before (Y=at−b, [G.M. Bristow, A.G. Sears, The use of novel parameters in the assessment of natural rubber processability, NR Technol. 18 (1987); H.G. Burhin, W. Spreutels, J.M. Campbell, MV2000 Mooney viscometer: Mooney relaxation measurements on raw polymers and compounded rubber stocks, Kautsch. Gummi Kunstst. 43 (1990) 431]). The results showed that a generalized Maxwell model, and the Wu–Abbott empirical model ( Y = 1 − a Ln ( t ) − ( b t / ( c + t ) ) ) [T. Wu, J.A. Abbott, Firmness and force relaxation characteristics of tomatoes stored intact or as slices, Postharvest Biol. Technol. 24 (2002) 59–68], recently used for describing stress relaxation of tomato flesh, allowed a better description of the relaxation curve for the samples studied than the power law or stretched exponential traditionally used. Moreover, the total relaxation time (τm) given by the generalized Maxwell model showed good correlation with the total gel content of the samples studied.