Postharvest Biology and Technology of Fruits, Vegetables, and Flowers

Chapter 8
Structural Deterioration of the
Produce: The Breakdown of Cell
Wall Components
Pradeep S. Negi and Avtar K. Handa
8.1 Introduction
Fruit ripening is a dynamic transitional period during which many easily perceived changes,
such as alterations in pigmentation, firmness, sweetness, and acidity take place. These
changes make fruit desirable for human consumption and capable of seed dispersal by
birds, animals, and environments. Fruit firmness is associated with several attributes including
crispness, mealiness, grittiness, chewiness, succulence and juiciness, fibrousness,
toughness, and oiliness. Additionally, development of various organoleptic components
such as sweetness, sourness, astringency, bitterness, and production of volatile compounds
leading to characteristic aroma is connected with fruit textural changes. Although most
of these changes impart desirable traits to various fruits and vegetables, some of the fruit
softening associated changes make them unacceptable for marketing. These include development
of off-flavors and off-odors with excessive softening of tissues. Textural softening
can also increase susceptibility to phytopathogens due to their proneness to solute leakage
that provide rich media for their growth, and resulting in severe losses during postharvest
storage and marketing (Prasanna et al., 2007).
Large economic losses results from inability to retard ripening-associated excessive
softening of fruits between harvest and marketing. These losses occur due to culling of
perishable commodities at field and packinghouses, grading, storage, transit, retail, and
consumer. In developing countries, theses losses can range between 10 and 100%, especially
due to phytopathogen-related tissue rotting of certain commodities. The economic
consequences of postharvest fruit softening have led to considerable interests of geneticists,
physiologists, biochemists, and in recent year’s molecular biologists to understand the
molecular basis of fruit softening. The last 40 years have seen a significant increase in our
understanding of biochemical changes associated to fruit textural modifications. Emerging
recombinant DNA technologies including reverse genetics have begun to provide some
answers. In this chapter we have described the relationship of cell wall chemistry and various
families of cell wall–modifying enzymes to the developmentally regulated softening
of fruit during ripening. Also discussed are various postharvest factors affecting structural
deterioration of fruit crops and potential of chemical or genetic means to reduce crop
losses.
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