Produce Degradation Pathways and Prevention

280 Produce Degradation: Reaction Pathways and their Prevention

the effect of cooling delays on weight loss and quality of mature green bell peppers
(Cantwell et al., 2001). The longer the cooling delays and the higher the produce’s
holding temperature prior to cooling, the greater the loss in weight, visual quality,
and texture of green bell peppers. Robinson et al. (1975) reported that temperature
was the single most important factor in successful storage of fresh produce, but that
minimizing evaporative losses was critical. They also noted that the rate of evapo-
ration for fresh produce was directly proportional to the water vapor pressure deficit
(wvpd) of its environment, and that the amount of evaporation that can occur was
limited by the amount of water the air can hold. Therefore, a reduction in water loss
can be achieved by limiting the rate of evaporation and by reducing the wvpd to a
minimum, or by limiting the amount of evaporation and by reducing the volume of
the air in the immediate environment.

9.7.1.1 Cooling of Harvested Fresh Produce

Cooling of freshly harvested produce is one of the first steps taken to extend shelf
life and quality. At harvest, produce temperature is close to ambient temperature but
may rapidly change depending on the holding conditions soon after harvest. The
higher the holding temperature soon after harvest, the higher the respiration rate,

TABLE 9.4
Mature Green Bell Pepper Weight Loss and Quality in Relation to Delays
to Cool at 25 or 37°C

Delay to

Cool (h)

Weight Loss

after

Delay (%)

Weight Loss

after

Storage (%)

Final

Weight

Loss (%)

Visual

Quality

Scorea

Dehydration

Scoreb

Firmness

(N)

0 0 2.06 0.97 8.5 1.2 19.7

At 25°C
3 0.15 1.91 1.39 8.1 1.2 21.0
6 0.36 1.87 1.48 8.1 1.5 22.5
9 0.52 2.35 1.78 7.5 2.4 21.5
12 0.69 2.93 1.86 7.2 3.0 19.3
18 1.04 1.61 2.08 7.3 3.0 17.4

At 37°C
3 0.25 1.62 1.19 8.6 1.2 20.9
6 0.60 1.66 1.50 8.3 1.5 19.9
9 1.33 1.67 2.30 7.5 2.3 16.6
12 1.80 2.10 2.52 6.0 2.8 14.2
18 3.25 1.64 3.07 3.6 3.4 10.7

aVisual score based on scale of 1 to 9; 1 = unsalable and 9 = excellent.
bDehydration score based on scale of 1 to 5; 1 = none and 5 = severe dehydration.
cN = Newtons.

Source: Cantwell, M. et al., Perishables Handling Q., 107, 17, 2001. With permission.