8 Innovative Environmentally Friendly Technologies to Maintain Quality of Durable Agricultural Produce
8.1 INTRODUCTION
8.1.1 BACKGROUND AND HISTORY OF POSTHARVEST TECHNOLOGIES
Abstract: There is an increasing imbalance between the demands of the First World for quality food uncontaminated by insecticidal residues, and the desperate need of Third World populations to maintain and protect their harvested grain from the deprivations of molds and insects so as to maintain a minimum level of food security.
In developed countries, loss of quality is particularly important. Although quantitative losses are generally low, quality is often degraded because of insect infestation or mold activity. Losses of biological origin such as those caused by grain or insect respiration or limited drying due to aeration in storage are common. These losses for cereals, on an annual basis, are usually less than 1%.
In developing countries, poor handling and storage methods under warm and humid climatic conditions promote rapid deterioration of the stored foodstuffs. In those countries, the major portion of grain and pulses (sometimes up to 80% of the national production) is kept on the farms for home consumption. Postharvest losses of food grain in developing countries have been conservatively estimated during the 1980s at 10–15% by the FAO’s Special Action Programme for the Prevention of Food Losses. For example, losses of corn due only to insects in farmers’ stores in Nigeria, Swaziland, and Kenya were in the order of 6–10%.
Increased public concern over the adverse effects of pesticide residues in food and the environment has led to the partial substitution of use of contact pesticides (typically organophosphates and pyrethroids) and fumigants by alternative control methods. Therefore, nonchemical and environmentally user-friendly methods of pest control in the postharvest sector are becoming increasingly important. It is worth noting that of the 14 fumigants listed some 20 years ago by Bond (1984), only 2 remain today in regular worldwide use, namely, phosphine and methyl bromide (MB). Methyl bromide kills insects relatively quickly, but it will be phased out in developed countries by 2005 and in developing countries by 2015, because of its contribution to stratospheric ozone depletion (UNEP, 2002). Although there are exemptions for quarantine and preshipment purposes, as well as the possibility to apply for exemptions where no alternative exists, the applicant has to demonstrate that every effort is being made to research alternative treatments. In contrast, phosphine remains popular, particularly in developing countries, because it is easier to apply than methyl bromide. However, many insects have developed resistance to phosphine over the last decade.
Grains can be stored for extended periods provided that there is no insect infestation and that their water activity is low enough to prevent microbial growth. However, quantitative or qualitative losses still occur. Qualitative losses, for example, may consist of changes in physical appearance, in nutritional degradation, in loss of germination capacity, in the presence of insects or their fragments, or in contamination by mold or the presence of mycotoxins. Some of these are difficult to detect visually.
If the moisture content is maintained sufficiently low, insects remain the main concern for the quality preservation of durable agricultural commodities. Therefore, in this chapter the major emphasis is placed on innovative friendly technologies addressed to the control of insect pests. Such methods fall into four main groups: A) physically based technologies that can be used to manipulate the storage ecosystem; B) application of phyto-extracts; C) use of pheromones; and D) biological control.
This chapter covers the main areas of progress in the understanding and adoption of novel postharvest technologies for stored-grain disinfestation and protection. An objective of this review is to indicate where new studies are required.
The widespread scientific activities on this subject resulted in the holding of several international conferences, such as the International Working Conferences on Stored-Product Protection held in Savannah, GA, in 1974 (Anonymous, 1975), in Ibadan, Nigeria, in 1978 (Anonymous, 1979), in Manhattan, KA, in 1983 (Anonymous, 1984), in Tel Aviv, Israel, in 1986 (Donahaye and Navarro, 1987), in Bordeaux, France, in 1990 (Fleurat-Lessard and Ducom, 1991), in Canberra, Australia, in 1994 (Highley et al., 1994), in Beijing, China, in 1998 (Zuxun et al., 1999), and in York, U.K., in 2002 (Credland et al., 2003). These meetings provided a platform for the useful exchange of information among the participating scientists and the reciprocal insemination of new ideas for further research.
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