Temperature Effects on Produce Degradation 607
commodity. This table can show, for example, that if a commodity has a shelf life
of 13 d at 20°C, it can be stored for as long as 100 d at 0°C but will last only about
4 d at 40°C.^6
The effect of reducing temperature on storage life is not uniform.^6 Only a small
improvement in storage life is achieved by small reductions at the upper end of the
temperature range. Much larger improvements are obtained by small reductions at
the lower temperatures, where even a change of 1°C can have a significant effect.
Excess energy from respiration, i.e., energy not used to maintain life processes,
is released in the form of heat, called vital heat. The amount of vital heat varies
with the type of product, variety, maturity or stage of ripeness, injuries, temperature,
and other stress-related factors. This heat, which is about 673 kcal per mole of sugar
utilized, must be considered in any temperature management program since it can have
TABLE 20.3
Typical Figures for Q 10
Temperature Q 100–10°C 2.5–4.0
10–20°C 2.0–2.5
20–30°C 1.5–2.0
30–40°C 1.0–1.5
Source:Saltveit, M.E., Respiratory metabolism, in The
Commercial Storage of Fruits, Vegetables, and Florist and
Nursery Crops, Gross, K.C., Yang, C.Y. and Saltveit, M.,
Eds., Agricultural Research Service, Beltsville, MD, 2002,
draft version of revised USDA Agriculture Handbook 66,
available at http://www.ba.ars.usda.gov/hb66/index.html.
(With permission.)TABLE 20.4
Effect of Temperature on the Rate of Degradation
Temperature (°C) Assumed Q 10 Relative Rate of Degradation Relative Shelf-life0 — 1.0 100
10 3.0 3.0 33
20 2.5 7.5 13
30 2.0 15.0 7
40 1.5 22.5 4Source: Saltveit, M.E., Respiratory metabolism, in The Commercial Storage of Fruits, Vegetables, and
Florist and Nursery Crops, Gross, K.C., Yang, C.Y. and Saltveit, M., Eds., Agricultural Research Service,
Beltsville, MD, 2002, draft version of revised USDA Agriculture Handbook 66, available at
http://www.ba.ars.usda.gov/hb66/index.html. (With permission.)