application of alternative food-preservation - Bentham Science

198 Application of Alternative Food-Preservation Technologies Corbo and Bevilacqua
Carbon Monoxide
Carbon monoxide is a colourless, tasteless and odourless gas, highly reactive and very inflammable. It has a low
solubility in water but it is relatively soluble in some organic solvents. CO has been studied in the MAP of meat
and has been licensed for use in the USA to prevent browning in packed lettuce. Commercial application has
been limited because of its toxicity and the formation of potentially explosive mixtures with air.
Noble Gases
The noble gases are a family of elements characterized by their lack of reactivity and include helium (He), argon
(Ar), xenon (Xe) and neon (Ne). These gases are being used in a number of food applications, e.g. potato-based
snack products.
LIMITATIONS OF MAP IN FRESH-CUT FRUIT AND VEGETABLES
Fresh produce is more susceptible to diseases because of increase in the respiration rate after harvesting; so, the
shelf life under ambient conditions is very limited. The respiration of fresh fruits and vegetables can be reduced
by many preservation techniques, like low temperature, canning, dehydration, freeze-drying, controlled
atmosphere, and hypobaric and modified atmosphere. Dehydration also controls the activity of microorganisms
by the removal of water under controlled conditions of temperature, pressure and relative humidity. The
controlled atmosphere packaging (CAP) is used for bulk storages. In this approach the composition of gases is
maintained in the package, so it requires continuous monitoring of gases. Freeze-drying is a very important
technique in which product volume remains the same as sublimation leads to direct removal of ice. But it is 2–5
times more expensive and slower as compared to other methods. Modified atmosphere packaging technology is
largely used for minimally processed fruits and vegetables including fresh, ‘‘ready-to-use’’ vegetables [15].
Fresh-cut fruit and vegetable products for both retail and food service applications have increasingly appeared in
the market place recently. In the coming years, it is commonly perceived that the fresh-cut products industry will
have unprecedented growth. Fresh-cut vegetables for cooking are the largest segment of the fresh-cut produce
industry; salads are another major category, as consumers perceive them as being healthy. Fresh-cut fruit is
growing very fast; however, processors of fresh-cut fruit products will face numerous challenges not commonly
encountered during fresh-cut vegetable processing. The difficulties encountered with fresh-cut fruit, require a
new and higher level of technical and operational sophistication.
Fresh-cut processing increases respiration rates and causes major tissue disruption as enzymes and substrates,
normally sequestered within the vacuole, become mixed with other cytoplasmic and nucleic substrates and
enzymes. Processing also increases wound-induced C2H4, water activity and surface area per unit volume,
which, may accelerate water loss and enhance microbial growth, since sugars become readily available, too [16,
17, 18]. These physiological changes may be accompanied by flavour loss, cut surface discoloration, colour loss,
decay, increased rate of vitamin loss, rapid softening, shrinkage and a shorter storage life. Increased water
activity and mixing of intracellular and intercellular enzymes and substrates may also contribute to flavour and
texture changes/loss during and after processing. Therefore, proper temperature management during product
preparation, refrigeration throughout distribution and marketing is essential for maintenance of quality.
The effect of modified atmospheres on the quality of many fresh-cut products (mushroom, apple, tomato,
pineapple, butterhead lettuce, potato, kiwifruit, salad savoy, honeydew, mango, carrot) has been extensively
studied and recently reviewed by Sandhya [15]. However little is reported about the safety of fresh-cut products.
Raw and minimally processed fruits and vegetables are sold to the consumer in a ready-to-use or ready-to-eat
form, without preservatives or antimicrobial substances and any heat processing before consumption. Therefore,
a variety of pathogenic bacteria, such as Listeria monocytogenes, Salmonella sp., Shigella sp., Aeromonas
hydrophila, Yersinia enterocolitica and Staphylococcus aureus, as well as some Escherichia coli strains may be
present on fresh fruits and in the related minimally processed refrigerated products [19, 20, 21]. In fact, the
number of documented outbreaks of human infections associated to the consumption of raw and minimally
processed fruits and vegetables has considerably increased during the past decades [22].
Moreover, the inefficacy of the sanitizers used, probably due to the inability of active substances to reach
microbial cell targets, makes difficult the decontamination of raw fruits and vegetables [19]. The presence of cut
surfaces, with a consequent release of nutrients, the absence of treatments able to ensure the microbial stability,