284 Produce Degradation: Reaction Pathways and their Prevention
have been found to provide a partial barrier to water vapor and gas exchange, thus
delaying shrinkage of cut produce and creating a modified atmosphere around the
commodity (Ben-Yehoshua et al., 1985; Ben-Yehoshua, 1987; Baldwin, 1994; Frank
and McLaughlin, 1997; Amarante and Banks, 2001). The edible coatings/waxes are
nontoxic and are used to enrobe some fresh produce to aid in maintaining high
relative humidity and freshness and prolong shelf life (Watada et al., 1996). An
edible coating is considered to be a thin layer of edible material formed naturally
on the food and applied in liquid form on foods by dipping, spraying, or panning.
The waxes act as sealants, cover the cuticle, and block pores on the surface, slowing
down ripening and, most important, reducing water loss. Banks et al. (1993) con-
cluded that surface coatings were important for resistance to water vapor diffusion,
internal atmosphere modification, respiration, and transpiration. Baldwin et al.
(1996) found that the addition of soy protein or peptides to coating material such
as CMC was effective in significantly reducing water loss and gas permeability.
Avena-Bustillos et al. (1997) found that edible caseinate-acetylated monoglyceride
films reduced moisture loss in celery by 75% and produced a higher water vapor
resistance in apples. McHugh and Senesi (2000) reported increased water barrier
properties with increased lipid concentration in coatings used in fresh-cut apples;
water vapor permeability varied between 69 and 325 g mm/kPa·d–1·m–2. The effec-
tiveness of waxes in reducing water loss has been reported in pears (Meheriuk and
Lau, 1988), tomatoes (Ghaouth et al., 1992; Park et al., 1994), citrus fruit (Hagen-
maier and Baker, 1993), green peppers (Lerdthanangkul and Krochta, 1996), and
cut apples and potatoes (Baldwin et al., 1996), and summarized by Guilbert et al. (1996).
Carrillo-Lopez et al. (2000) found that the treatment of mangoes with “Semperfresh”
edible coating at concentrations of 8, 16, and 24 g/L resulted in firmer fruit and less
weight loss compared to untreated fruit. Similarly, Hoa et al. (2002) found that coating
mangoes with formulations containing carnuba wax, shellac, zein, and cellulose deriv-
atives retarded the loss of firmness. Waxes are commonly used on products such as
apples, cucumbers, eggplants, peppers, and citrus fruits.
9.7.5 PROCESSING TREATMENTS
Fruits and vegetables that have large surface area:weight ratios are susceptible to
water loss and shriveling. Although the problem can be alleviated by rapid cooling
soon after harvest and storing at high relative humidity, produce that is chill-sensitive
deteriorates rapidly. Gonzalez-Aguilar et al. (1999) found the combination of hot
water treatment of bell peppers at 45C or 53°C and storage in low-density polyeth-
ylene bags resulted in tremendous quality improvement, including firmness, reduc-
tion in water loss, retardation of color change, and alleviation of chilling injury.
Garcia et al. (1996) reported that strawberries dipped in 1 to 4% calcium chloride
solutions at 25 and 45°C, followed by 3 days of storage at 18°C, retained quality
characteristics. Berries treated with 2 and 4% calcium chloride solutions at 25 and
45°C lost less weight than controls. They attributed the reduced weight loss to
reduced water permeability of the fruit. Bangerth et al. (1972) found that calcium
chloride treatment of apples resulted in firm apples that retained more ascorbic acid
and had reduced internal breakdown.