Dried Fruits and Tree Nuts

CONTENTS 20.1 Introduction ...................................................................................................................... 507 20.2 Applications for Insect Control...................................................................................... 508

20.2.1 Dried Fruits........................................................................................................ 511 20.2.2 Tree Nuts............................................................................................................ 515 20.2.3 Combinations with Other Treatments ........................................................... 517

20.3 Effects on Quality ............................................................................................................ 519 20.3.1 Almonds (Prunus dulcis) .................................................................................. 519 20.3.2 Apricots (Prunus armeniaca)............................................................................. 519 20.3.3 Chestnuts (Castanea sativa)............................................................................... 520 20.3.4 Dates (Phoenix dactylifera)................................................................................. 520 20.3.5 Figs (Ficus carica) ............................................................................................... 520 20.3.6 Hazelnuts, Filberts (Corylus spp.) ................................................................... 521 20.3.7 Macadamia (Macadamia integrifolia)................................................................ 521 20.3.8 Pecan (Carya illinoinsis) .................................................................................... 521 20.3.9 Pine Nuts (Araucaria spp.) ............................................................................... 521 20.3.10 Pistachio (Pistacia vera) ..................................................................................... 521 20.3.11 Raisins (Vitus vinifera) ...................................................................................... 522 20.3.12 Walnuts (Juglans regia) ..................................................................................... 522

20.4 Conclusions....................................................................................................................... 522 20.5 Future Research Needs ................................................................................................... 523 References.................................................................................................................................... 523

Dried fruits and tree nuts are relatively high-value products used primarily for snack foods or as confectionary ingredients, and their successful marketing requires strict attention to quality control. The United States alone produces nearly 1.5 million metric tons each year of almonds, hazelnuts, macadamias, pecans, pistachios, walnuts, dates, figs, prunes, raisins, and dried apricots, worth more than $3 billion (USDA, 2007). These are also valuable products for the foreign export market, important to the economies of such major producers as the United States and Turkey. Dried fruit and tree nuts typically have one or more preharvest insect pests that feed

directly on the product and are capable of causing considerable damage and quality loss (Simmons and Nelson, 1975). Although many of these may be present at the time of

harvest and are often brought into storage, they generally do not reproduce under storage conditions (Johnson et al., 2002). However, because they may continue to feed and cause additional damage, and often present phytosanitary problems for processors, they are considered postharvest pests. Feeding damage by these insects also may provide entry to aflatoxin-producing molds (Aspergillus spp.) (Campbell et al., 2003). Initial disinfestation of an incoming product is sufficient to control these pests and reduce their damage. These commodities are also susceptible to attack by a number of common stored product moths and beetles, the most serious being the Indianmeal moth, Plodia interpunctella (Simmons and Nelson, 1975). Because stored product pests are capable of repeated infestation during storage, long-term protective treatments or repeated disinfestation treatments are necessary for their control. Current insect control measures for dried fruit and nuts depend largely on fumigation to

disinfect large volumes of incoming product during harvest, as well as to control storage infestation (Johnson, 2004). Methyl bromide, a fumigant used in a wide range of postharvest applications, is scheduled for worldwide withdrawal from routine use as a fumigant in 2015 under the Montreal Protocol on ozone-depleting substances (UNEP, 2006), and its use has already been severely restricted in developed countries. Resistance to phosphine, often used as an alternative to methyl bromide for dried fruit and nut crops in developed countries, has been documented in many insect populations (Benhalima et al., 2004), and some regulatory agencies have expressed concerns over worker safety with this compound (Bell, 2000). Sulfuryl fluoride, long used for structural fumigation, has recently been registered for commodity fumigation in several countries including the United States (Prabhakaran and Williams, 2007), but reduced toxicity of this compound against insect eggs and at lower temperatures (Bell and Savvidou, 1999) may limit its applicability. Moreover, there is a mounting pressure against the general use of chemical fumigants due to atmospheric emissions, safety, or health concerns, and an increased interest in organic food production, resulting in efforts to develop nonchemical technologies as alternative control methods for insects. Among these technologies are low and high temperatures, irradiation, andmodified atmosphere (MA) and controlled atmosphere (CA). Dried fruits and nuts, like most low-moisture, durable commodities, often tolerate

extreme MA and CA (very high CO2 and=or very low O2) at levels used to control insects. More than 25 years ago, the U.S. Environmental Protection Agency approved carbon dioxide, nitrogen, and combustion product gases as a means to manage insects infesting raw and processed agricultural products, including dried fruits and tree nuts (Johnson, 1980, 1981). While current insect control measures for dried fruits and nuts still rely on fumigation, there is some limited commercial use of MA and CA for these products, primarily for organic product lines. This chapter will discuss the potential applications and effect on product quality of MA and CA treatments for insect control in dried fruits and tree nuts.