Nutrient Loss 249
inevitable. Intentional losses occur due to intentional removal of parts of fruits and
vegetables, for example, during peeling. Accidental or avoidable losses occur as a
result of inadequate control and handling of food materials. The major concern from
a food-processing point of view is the inevitable losses that represent the loss of
heat-labile nutrients destroyed to some degree by heat. The extent of these losses
depends on the nature of the thermal process (blanching, pasteurization, or steril-
ization), the raw materials, and preprocessing preparation, because operations such
as size reduction (slicing and dicing) result in increasing losses through increasing
the surface-to-volume ratio. All water-soluble vitamins and minerals as well as some
parts of soluble proteins and carbohydrates are susceptible to losses during produce
processing. In any processing operation, therefore, the emphasis is on reducing the
inevitable nutrient losses through adoption of appropriate time–temperature process-
ing conditions as well as environmental factors (pH and concentrations) that will
ensure maximum retention of the nutrients.
Because processing in fresh fruits and vegetables is a broad term that is difficult
to define, for the scope of this chapter those treatments to fruits and vegetables that
begin after harvest before consumption will be discussed. These treatments include,
but are not limited to, heating, refrigeration, dehydration, chemical treatment, and
radiation. Changes in the composition of raw fruits and vegetables, which may
decrease their nutritive value, can occur after harvest, during transportation, holding,
handling, processing, and subsequent storage and distribution. After they are har-
vested, fruits and vegetables are still physiologically active. Enzymatic and respira-
tory processes may bring about profound changes unless they are controlled. The
demand for fresh, healthier, convenience-type fresh-cut fruits and vegetables that
are minimally processed has increased tremendously in the past decade (Zhang and
Farber, 1996; Watada et al., 1996). In the U.S., for instance, the sales of fresh-cut
fruits and vegetables exceeded U.S.$19 billion in the year 1999. The minimally
processed fruits and vegetables, however, are generally more perishable than the
original raw materials.
Injury stress due to procedures such as peeling, cutting, shredding, trimming,
slicing, coring, and grating greatly increase tissue respiration and lead to various
biochemical deteriorations such as browning, off-flavor development, and texture
breakdown. Moreover, minimal processing may increase microbial spoilage of the
product through transfer of skin microflora to the fruit and vegetable tissues (Bolin
and Huxsoll, 1989; Pittia et al., 1999). For example, fresh-cut vegetables support
the survival and growth of foodborne pathogens such as Listeria monocytogens, and
these foods have been implicated in outbreaks of foodborne illness (Nguyen-The
and Carlin, 1994).
Improvement of the shelf life of fresh and minimally processed fruits and
vegetables may be achieved by applying one or a combination of many of the classic
preservation procedures such as heat treatment, refrigeration, dehydration, fermen-
tation, and additives. The effectiveness of one or several combinations of these
preservation methods on the shelf-life extension of minimally processed products
has been evaluated for many different categories of foods (Bolin and Huxsoll, 1989;
Pittia et al., 1999). The choice of an optimum multiple preservation method is very
difficult due to the various and complex biochemical and microbiological changes