Postharvest Physiology and Hypobaric Storage of Fresh Produce (Cabi)

Postharvest Physiology and Hypobaric Storage of Fresh Produce by Stanley P. Burg (CABI Publishing) Postharvest Physiology and Hypobaric Storage of Fresh Produce is dedicated to preserving the existing theoretical knowledge, applied research and technology relating to hypobaric storage in order to promote an understanding and appreciation of the method. The author's views regarding the postharvest behaviour of commodities at atmospheric pressure were developed in an attempt to explain the documented advantages of LP vs. CA storage and do not always agree with currently accepted concepts in postharvest physiology. Scientific readers may respond to some of this background information with scepticism and disapprobation, but if at the end of the day researchers are motivated to test these concepts, Postharvest Physiology and Hypobaric Storage of Fresh Produce will have been well worth the time and effort expended in writing.`Controlled atmosphere storage has been the subject of an enormous number of biochemical, physiological and technological studies, yet it is still not known precisely how it works' (Thompson, 1998). Lipton (1977b) commented `It seems after 50 years of work on CA storage, we ought to at least try to see whether there is a common basis for our observations'. LP theory has been developed to a higher degree than the present empirical understanding of CA, but this knowledge is difficult for postharvest physiologists to evaluate unless they possess an intimate familiarity with thermodynamics, mass transport, refrigeration, vacuum technology and the physical laws applicable to an environment resembling that in which earth satellites orbit. It is not possible to plan an LP experiment and interpret its result without considering the manner in which mass and heat are transferred in the medium vacuum range and the influence this has on water loss and the gaseous gradients that arise within a commodity's intercellular spaces. The physical laws governing these processes will be reviewed to assist the reader in understanding the mechanisms that give rise to the unusual results attainable with LP described in the following Table. Postharvest physiologists can easily comprehend the biological factors, but may find the physical computations distracting. Therefore, relevant equations are presented in the Appendix, and computations are included as Examples at the end of each chapter, which the reader can ignore if he so chooses because the text summarizes each example's conclusions and interprets its significance.The low-pressure storage method originally was called LPS or LP. Later, Tolle (1969, 1972) suggested the term `hypobaric'; Rynearson proposed the trade name `DormavacTM' (dormant in a vacuum) to describe Grumman's intermodal hypobaric container and the original `wet' LP method; more recently the service mark `VacuFresh' became synonymous with the `dry' LP method, and `TransVac' with a new `square' LP container design. Frequently used abbreviations throughout the text include RH (relative humidity), CA (controlled atmosphere storage), MA (modified atmosphere storage), NA (normal atmosphere storage), ICC (internal concentration of CO2) and IEC (internal ethylene concentration). Other abbreviations are defined in the index or when they first appear. To simplify comparisons between results obtained at atmospheric and subatmospheric pressures, the O2, CO2 and NH3 concentrations are expressed as per cent [O2], [CO2] and [NH3], where 2% [O2] refers to an O2 partial pressure of 0.02 atm. According to international conventions, the pressure-unit conversion constants are: 1 atm (standard) = 101.33 kPa (kilopascals) = 1013.3 mbar (millibar) = 760 mm Hg (mm mercury) = 760 torr = 14.696 psi (lb/in2).