Mechanisms of Food Additives, Treatments, and Preservation Technology 325
Several authors have reviewed the nonthermal processes and their applications in
food preservation (Kader, 1986; Barbosa-Cánovas et al., 1998; Gunes et al., 2001).
Gamma rays and, to a lesser extent, x-rays and electron emission are used for
destruction of microorganisms or inhibition of physiological changes in food. Some
examples of commercial application of irradiation in produce processing are given
in Table 10.11. Promising results were found in delaying ripening of whole fruits
by irradiation (Kader, 1986), but irradiation of cut fruit could induce undesirable
changes in texture (Gunes et al., 2001).
Food products, usually in flexible packaging, can be subjected to high hydrostatic
pressure in the range 300 to 1,000 MPa for several minutes. The method permits
inactivation of microorganisms and enzymes without the degradation of flavor (Cheftel,
1995). Recent applications in fruit and vegetable processing summarized by Ohlsson
(2002) are shown in Table 10.12. The application of high pressure has several
limitations. High pressure could disrupt the structure of whole or cut fruit or vege-
tables. Some enzymes such as polyphenoloxidase, peroxidase, and lipoxygenase
may be resistant to high pressure, and in some cases enzymatic activity could increase
due to the changes in protein conformation and bacterial spores that are resistant to
TABLE 10.11
Application of Irradiation in Processing of Produce
Application Dose range (kGy) Product
Sterilization 7–10 Herbs, spices
Control of molds 2–5 Fresh fruits
Extension of chill life (up to 1 month) 2–5 Fresh soft fruits (strawberries, etc.)
Disinfestations 0.1–2 Fruits, grains, cocoa beans
Inhibition of sprouting 0.1–0.2 Potatoes, garlic, onions
Source:Fellows, P., Food Processing Technology: Principle and Practice, CRC Press, Boca Raton, FL,
2000c, Part 4.
TABLE 10.12
Application of High Pressure in Processing of Produce
Products Process Conditions
Jams, fruit dressings, fruit sauce topping,
fruit jelly
400 MPa, 10–30 min, 20°CMandarin juice 120–400 MPa, 2–20 min, 20°C
(and additional heat treatment)
Avocado 700 MPa, 600–800 L/h
Orange juice 500 MPa, 5- or 10-min cycles including 1 min hold
Source: Ohlsson, T., in Minimal Processing Technologies in the Food Industry, Woodhead Publishing
Limited and CRC Press, Boca Raton, FL, 2002, p. 4.