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High-Energy, Nutrient-Dense Emergency Relief Food Product 3 Processing and Packaging of the Emergency Food Product Developing energy-dense nutritional foods that can be packaged and stored for extended periods of time in environments that vary from arctic to tropical presents a challenge to the processor. In an emergency situation these products must also meet the nutritional needs of all age groups from infants to adults, and be sufficiently palatable to be consumed for up to two weeks as the sole food. Nutrient profiles for an emergency food product (EFP) can and have been developed (see Chapter 2), but the required useful life of the product will be met only through careful consideration and selection of ingredients, processing techniques, and packaging materials. Key considerations include microbiological and chemical safety, dispersability, and ease of use. DESIRABLE CHARACTERISTICS OF AN EMERGENCY RELIEF FOOD PRODUCT The use of a few nutrient-dense products in a variety of emergencies by relief organizations such as the United Nations High Commissioner for Refugees, the World Food Programme of the United Nations, and the International Committee of the Red Cross and Red Crescent, has resulted in anecdotal information about the desirable characteristics of such foods. These characteristics should be taken into consideration during prototype development in order to develop a superior EFP. Historically, some of the most important emergency relief food products available in Europe, particularly the most successful one—the Norwegian BP-5—were not developed with food relief in mind. They were intended to
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High-Energy, Nutrient-Dense Emergency Relief Food Product be rations stowed in lifeboats for use in the event of passengers and crews having to abandon ship. Nevertheless, their use in the field during diverse emergencies, such as the Ethiopia and Eastern Sudan famine of 1985 to 1986 and the more recent Balkans conflicts, have permitted an evaluation of their efficacy from the standpoint of nutrition, acceptability, ease of delivery, and some practical aspects such as potential for diversion seldom discussed in refereed publications. The following sections provide some aspects that representatives from various relief organizations urged be considered in developing specifications for the EFP. Packaging the EFP for Airdrop or Surface Delivery Considering that the EFP is for use at the onset of emergencies, when infrastructure destruction and security considerations make it impossible to run feeding centers, the EFP should be available in a packaging modality amenable to low-altitude airdrop as well as delivery on land. There have been attempts to configure EFPs in ways that facilitate air delivery without damaging the product upon impact on the ground or hurting the intended recipients. Such packaging must also allow for dissemination of the product over a wide area so that it may reach many people. (Past experience indicates that concentrating the drop in the form of parachuted pallets, for example, contributed to hoarding, thus defeating the primary objective of ample distribution of the food relief, and also contributed to its diversion to unintended uses). Packaging the EFP to Discourage Diversion Information provided by relief organizations indicate that the high energy content of some EFPs, the density of nutrients in them, and the ease with which they may be carried has resulted in these products being collected by military combatants in emergency situations involving armed conflict. Biscuit-type EFPs are easily diverted to become military rations in emergencies involving armed conflict to the detriment of and even at a risk to the intended civilian recipients. The diversion is facilitated when the shape and size of the unit makes it easy to fit into the side pockets of military wear; rectangular, thin presentations seem to be best suited for this purpose. In addition, the use of eye-catching, glittery, space-age packaging materials encourages such diversion. It has been, therefore, the consensus among representatives of several relief agencies that the shape and size of the outside package of a successful EFP should be uncomfortable to carry in military pockets and should be made of nonlustrous materials. Furthermore, separation of the ration into smaller portions that cannot easily be rewrapped after opening also discourages diversion while aiding in apportioning the ration among children and adults.
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High-Energy, Nutrient-Dense Emergency Relief Food Product Packaging to Facilitate Distribution and Consumption of the EFP and Reuse of its Secondary Package Based on information from relief organizations, other anecdotal considerations for a superior EFP are the size of the unit and the potential for reuse of the secondary package. It is important that the size of the total unit and its breakdown into meal portions are designed so that adults can apportion it to individual sittings. Meal-size portions should be scored to facilitate partitioning them for children. It is also important that the primary and secondary packages be able to serve additional uses in emergency situations. For example, a combustible primary package for emergency rations has found use in various emergencies as fuel for cooking. The secondary package may also be put to good use by recipients. For example, tin cans used to package emergency rations have been used as containers for water, as storage boxes, and even as metal shingles for building roofs after being pounded flat. In addition, from the technical standpoint, this type of secondary packaging might be very helpful in maintaining the integrity of the EFP against impact and pressure damage, insect and rodent attack, and other environmental challenges during transport, storage, and delivery. Therefore, the secondary package for the EFP should be designed such that it could afford secondary uses to the recipients. Characteristics of Similar Ration Products Conventional and novel technologies were considered for manufacturing the EFP. Combining some of these technologies may be the best approach to optimize the stability of the product and preserve its nutritional and sensory qualities. Dehydration, infusion, compression, and cold extrusion are some examples of processing technologies to be considered. These processes have been tested by the U.S. Army to obtain calorie-dense rations (Briggs et al., 1986; Schulz et al., 1992). A caloric density of 1.1 kcal/cc can be obtained using dehydration and compression. Higher caloric densities (up to 5 to 6 kcal/cc) are also possible using extrusion. The U.S. Air Force General Purpose (GP) Survival Packet ration for aircraft and life rafts, in turn, includes a variety of compressed bars such as a shortbread bar, a chocolate chip bar, a granola bar, and a corn flake cereal bar. The GP is designed to be consumed for periods of less than 5 consecutive days and contains approximately 100 g of carbohydrate and a low protein level (< 8 percent of calories) to counteract the effects of starvation and to conserve body water. This ration provides 1,447 kcal with 18 g of protein (5 percent of calories), 202 g of carbohydrate (56 percent of calories), and 64 g of fat (39 percent of calories). Its storage requirement is 5 years at 80º F and 1 month at 140º F (SBCOMM, 2001a).
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High-Energy, Nutrient-Dense Emergency Relief Food Product The Meal Ready-to-Eat, Individual (MRE) is the standard military ration developed to support the individual soldier in all the U.S. Armed Forces (Army, Air Force, Navy, and Marine Corps). The MRE replaced the C Ration in the early 1980s and has since been continuously updated. It is designed to serve as the sole source of food for up to 10 days in a field environment, until group rations are available. Its use has in many situations been for longer—up to 145 days were reported during the Gulf War in 1993. Feedback from Operations Desert Shield and Desert Storm suggested that soldiers would consume more if their preferences were taken into account (IOM, 1993). Improvements have focused on revising items to make the rations more acceptable and to expand variety (SBCOMM, 2001b). For example, the MRE bread is a pouch bread (Natick Research, Development, and Engineering Center, 1993) that contains glycerol, sucrose esters, lipids, and sorbic acid to extend shelf life up to 3 years, and has received high hedonic ratings (Hallberg and Chinachoti, 1992). This is now in every MRE ration. The average equilibrium pH and water activity of this bread are 5.0 and 0.86, respectively. The bread is further preserved by controlling oxygen content and initial microbial load (Hallberg et al., 1990; Powers and Berkowitz, 1990). In an investigation to develop a high-energy biscuit for use as an EFP in disaster relief, low-moisture (3.5 percent) biscuits were prepared using a traditional baking method, with formulation and processing strategies as the means to control caloric density and sensory quality (Young et al., 1985). The products were highly acceptable to sensory panels made up of children both in England and India. This shows that traditional processing methods—perhaps in combination with some of the novel MRE technologies described above—can be used to produce baked EFPs such as biscuits having desirable sensory and nutritional qualities and long shelf life. Role of Water Activity, Water Mobility, and Water Content in Packaged Food Products Three aspects of water are important to consider in describing a food system: water activity (aw), water mobility, and water content. Water activity is defined as the ratio of partial pressure of water in the product over that of pure water at the same temperature. The concept of aw was first put forward in the early 1950s, as a means of explaining the availability of water for chemical and biological reactions. It has been a useful tool in the food industry for many years and it is particularly useful when dealing with intermediate and high moisture biological systems (Ruan and Chen, 1998; Taoukis et al., 1988). The rate-limiting step in a chemical reaction is frequently associated with the mobility of water and its ability to participate in those reactions. At low aw, the binding of water (monolayer moisture) to components of the system makes it unavailable as a solvent. As aw increases, water exists in multilayers and is more mobile.
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High-Energy, Nutrient-Dense Emergency Relief Food Product Solvation and reactant mobility increase, so biological and chemical changes occur. This classic general relationship between moisture content, aw, and reaction rate was characterized over 30 years ago (Labuza, 1971). Water activity is used to predict the stability of food systems and quality changes likely to occur. However, in the past 10 years there have been numerous papers pointing out the limitations of the concept (Frank, 1991; Ruan and Chen, 1998; Slade and Levine, 1991). There are practical and theoretical concerns because aw measurement assumes that the food system is at equilibrium, a condition where the partial vapor pressure above the food system is the same as that of the water within it (Ruan and Chen, 1998). Since most food systems are not in equilibrium, this frequently does not hold true. Water mobility, as measured by nuclear magnetic resonance, is thought to be a more accurate way of determining the “availability” of water. Slade and Levine (1992) proposed the “polymer” approach to describe the role of water in food systems as a plasticizer that affects the glass transition temperature, which, in turn, could help explain the relationship between moisture and reaction rates (Nelson and Labuza, 1994). In practice, the use of aw as a means to predict product stability remains important, while the polymer science approach can be viewed as a more generalized theoretical explanation (Reid, 1995). Water activity is a better indicator of food product susceptibility to spoilage than is water content. Dried foods normally contain 2 to 20 percent moisture, corresponding to aw in the range 0.20 to 0.60. In contrast, intermediate moisture foods (IMFs) normally contain 15 to 40 percent total moisture and have an aw of 0.60 to 0.85 (Jayaraman, 1995; Karel, 1973; Sloan et al., 1976). PROCESSING CONSIDERATIONS Moisture control, mostly by dehydration, to lower the aw of the product is considered critical to attaining the required shelf life of the EFP of 2 to 3 years. The basic principle underlying drying and IMF technologies is the premise that water—the universal solvent—can become a limiting factor for spoilage and pathogenic microbial growth in foods when it is adequately reduced to low enough levels (Bone, 1973; Davies and Birch, 1976; Erickson, 1982; Gould, 1985; Rahman and Labuza, 1999). This reduction in moisture content and aw is sometimes accompanied by the use of other preservation factors such as chemical preservatives (e.g., antimicrobial agents, antioxidants, or antibrowning compounds), reduction of oxygen by vacuum and/or gas flushing techniques with maintenance through means of oxygen barrier packaging and/or oxygen-absorbent materials (oxygen scavengers), pH adjustment, and selection of packaging designs that protect the food from light, moisture, and environmental contamination. In the case of the EFP, moisture plays a critical role in determining microbial, sensory, chemical, and physical stability.
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High-Energy, Nutrient-Dense Emergency Relief Food Product Extrusion High-temperature, short-time extrusion cooking has been extensively applied in IMF and dried food production. Basic phenomena in extrusion cooking have been described by many (Harper, 1978, 1979, 1988; Linko et al., 1981; Rossen and Miller, 1973; Smith, 1982). In an extruder, the raw food material is subjected simultaneously to heat, pressure, and shear within a short time. Desirable product functional characteristics are typically controlled by altering the feed composition and extrusion process parameters. Water is always an integral part of physicochemical processes (e.g., gelatinization of starch and protein denaturation and plasticization) that determine the final textural characteristics of an extruded product. Extrusion can be applied to produce foods having various moisture levels, from dry IMF products (e.g., puffed snacks and ready-to-eat breakfast cereals) to soft, moist ones. Production of modern IMFs can belong to either one of three categories: (1) moist infusion, in which solid food pieces are soaked and/or cooked in a solution having low aw, (2) dry infusion, where initial dehydration is followed by soaking the food in a solution having low aw, and (3) blending, in which the components are weighed, blended, cooked, and extruded (Erickson, 1982). Extruded IMF products are also considered thermally processed as high-temperature, short-time (HTST). This not only helps to further preserve the product from potential microbial growth and adverse enzymatic action, but also can help reduce the amount of preservatives that would be necessary otherwise. HTST processes are rapid by definition, so little destruction of vitamins or loss of protein quality are expected. According to Harper (1988), heat-stable B vitamins and pantothenic acid are stable under extrusion conditions. However, oxidation of ascorbic acid or carotenoids could occur, particularly in puffed products, so puffed processing is not recommended for the EFP. It may be possible to hot extrude some combination of the ingredients, such as a protein and carbohydrate mixture, and then combine it with other ingredients (e.g., fat) in a compressed bar. Microencapsulation might be used for some nutrients and flavors that are mixed into a compressed bar formulation, given that most encapsulation materials are not intended for heat-processed foods. Spray coating of some ingredients after heat processing might also provide ways of incorporating heat labile ingredients during manufacturing of the EFP, as is done in breakfast cereals (Caldwell et al., 2000). Thus, the more stable vitamins might be included in the extrusion mix and others incorporated later (e.g., ascorbic acid and thiamin). Maillard Browning Reaction The Maillard reaction leads to brown color and to the appearance of new odors and flavors. The reaction involves reducing sugars and amino acids. It is a
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High-Energy, Nutrient-Dense Emergency Relief Food Product series of reactions that start with the formation of Amadori compounds from aldose or hexose carbonyl compounds condensing with free amino groups of amino acids or protein. The condensing product is a Schiffs base that later becomes aldosylamine, and this, in turn, is converted into ketosamines in the Amadori rearrangement. The final step involves formation of melanoidins, which are brown nitrogenous polymers or copolymers. Due to the complexity of Maillard reactions and their dependence on multiple factors (e.g., pH, temperature, composition of the medium, and moisture), it is difficult to predict the extent of browning. Sugars with different degrees of reducing power greatly influence the reaction kinetics. Water also affects it in a variety of ways. For example, a concentration of solids increases the reaction rate because of a reactant concentration effect; further concentration of solids leads to a reduced rate as the reactant mobility is decreased. In highly concentrated systems, the Maillard reaction is inhibited or retarded until, at some point, caramelization is more likely to occur than Maillard. Generally, the activation energy of the Maillard reaction increases with decreasing moisture content, suggesting that mobility retardation may be the rate-limiting factor (Labuza and Saltmarch, 1981). There is an aw range where maximum Maillard reaction occurs that depends on: (a) the extent of the dilution effect at the high-moisture end, and (b) the limited mobility of reactants at the low-moisture end. For instance, the maximum aw range in apple is 0.53 to 0.55, whereas in dried anchovy it is 0.93 (Labuza, 1980). Unfortunately, most of the data available on reaction kinetics of the Maillard reaction is limited to aw values higher than 0.3 (Eichner and Karel, 1972; Warmbier et al., 1976). This suggests that if the EFP had an aw below 0.3, it would have an extended shelf life. Additionally, not much information is available on very high moisture systems that are believed to have slower reaction rates. From an equilibrium consideration, a Maillard reaction is not favored at high moisture because the advanced reaction and the early formation of a Schiff base involve removal of water (Hodge and Osman, 1976). One of the nutritional implications of this reaction is a possible decreased digestibility and the loss of reactive amino acids, such as lysine (Kaanane and Labuza, 1989; Labuza 1994; Saltmarch and Labuza, 1982). This has been related to the cross linking of proteins, as demonstrated in freeze-dried meat (Barnett and Kim, 1997). In related work using an MRE chicken-a-la-king stored for 3 years between 4º and 30º C, Barnett and Kim (1997) reported that textural and sensory deterioration occurred much before the observed decrease in nutritive value. The Q10 (i.e., the increase in the rate constant as temperature is increased by 10º C) in military MREs has been reported as 3 to 4, suggesting that under abusive storage conditions, a decrease in nutritive value in terms of reduced digestibility and loss of lysine can occur. From the lysine-loss data, an estimation of the loss in nutritive value of the proteins in chicken meat heated at 73º C for 8 days in a high concentration of reducing sugar has been calculated to be about 13 percent (Barnett and Kim, 1997). If the above Q10 is assumed for the browning reaction, heating for 8 days
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High-Energy, Nutrient-Dense Emergency Relief Food Product at 73º C would correspond to a storage for 22 years at an ambient temperature of 23º C, which exceeds the military shelf-life requirement of 3 years (ambient). Unfortunately, this information applies to chicken protein, but the EFP would contain only vegetable proteins. Therefore, the validity of this effect would need to be tested using EFP prototypes and conditions of storage and use simulating those expected during actual use of the EFP. Nevertheless, the key implication of this issue is that although the sensory quality may decrease and the nutritive value, to a lesser extent, may also be reduced because of the Maillard reaction, proper selection of ingredients for the EFP can help minimize sensory deterioration (e.g., appearance of brown color and firmer texture) and keep its nutritional quality from being adversely compromised. Microencapsulation Microencapsulation provides a physical barrier to oxygen, metal catalysts, and other pro-oxidants. This type of technology has been used in the food industry for many years, but a wide range of patented processes have been developed in recent years (Brazel, 1999; Risch and Reineccius, 1995). The protection of nutrients and other unstable additives is made possible by microencapsulation formulations that can allow controlled release of the nutrient during digestion as well as preserve it during storage (Deasy, 1984; Kondo, 1979). By using microencapsulation, flavor, color, and texture can be improved, thus making the product more acceptable. The selection of shell material for microencapsulated nutrients will depend on the material being protected, processing needs, and storage stability concerns (Brazel, 1999). Capsule shell-wall materials are food additives by definition, and include polysaccharides (e.g., alginates, agarose), proteins (e.g., caseinates, zein), and fats. The water or oil solubility of the component to be protected will dictate the shell material composition (Brazel, 1999). Diffusion of oxygen and catalysts in the aqueous matrix of a food is dependent on the amorphous or crystalline nature of the aqueous phase (Shimada et al., 1991), and it has been proposed that the glassy-rubbery transition temperature (Tg—the temperature at which a rigid, amorphous, glassy material becomes molten and rubbery) plays a key role in governing oxidation of lipids embedded in the matrix (Roos and Karel, 1991). The free volume theory implies that gas diffusion through intermolecular spaces in the barrier (i.e., the continuous matrix in a dried micro-emulsion containing the oil droplets) depends on the glassy or rubbery state. As a glassy amorphous material undergoes a glass transition it gains a greater intermolecular freedom that can be described as the increase in molar free volume. A crystalline solid is a perfect barrier to diffusion and thus diffusion rate would depend on the intricacy of the barrier. In a system where water and oxygen diffusion occur simultaneously, the penetration front of water into a glassy, hydrophilic region would result in a decrease in Tg, with possible swelling or other structural change (e.g., collapse) at the hydration front
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High-Energy, Nutrient-Dense Emergency Relief Food Product as the polymer relaxes, transforming into a rubbery material depending on the time frame of the relaxation process with respect to diffusion time. This is expected to have a strong influence on oxygen diffusion (Chinachoti, 1998). Therefore, migration of oxygen and other small molecules depends on polymer chain flexibility that can “flip-flop” according to local chain mobility, which creates openings or holes for small molecules to travel through. This mobility depends on the state of hydration. The microstructure of microencapsulated oil has been reported to be a critical factor (Hardas et al., 2000, 2002; Ponginebbi et al., 2000). Oxidation rates of surface and encapsulated lipids have been shown to follow various mechanisms depending on the physical integrity and mobility of the matrix. Hence, the effect of moisture on oxidation of surface and encapsulated lipid fractions can vary widely (Hardas et al., 2002). Vitamins and minerals are often encapsulated to prevent unpleasant flavors and to prevent oxidation. Labile components such as fat-soluble vitamins are blended with lipids in emulsion droplets as part of the encapsulation process. Proper selection of surfactants that are antioxidants is advised, and care must be taken to ensure emulsion stability. To prevent easy moisture penetration, the encapsulation matrices should not have a low Tg. However, for enhanced bioavailability, they should disintegrate upon rehydration in the mouth or upon adding water. Capsule materials that ensure release of the nutrient during digestion are usually hydrophobic fats or waxes, but some cellulose and protein derivatives can be used (Brazel, 1999). Microencapsulation has been shown to greatly retard the oxidation of some oils that are rich in unsaturated and polyunsaturated fatty acids (Lin et al., 1995; Velasco et al., 2000). Typically, the oil is homogenized in water with the aid of an emulsifier and the resultant mixture is rapidly dried—most often in a spray drier—to yield a powdered, encapsulated product. Numerous encapsulation formulas have been tried; those that result in the highest amount of oil in the core of the particle have the best stability. Combination of antioxidants such as Δ-tocopherol (Han et al., 1991) and ascorbic acid or α-tocopherol and ascorbyl palmitate (Kaitaranta, 1992) may be used for additional protection. However, very few investigations have focused on the effect of storage and antioxidants on the oxidation of surface (free) and encapsulated lipids in microencapsulated fish oil (Velasco et al., 2000). In addition, the physical changes from amorphous to crystalline discussed above are factors that remain to be further investigated in order to improve product stability. Coating or encapsulation is routinely done in the manufacture of fortification nutrients and flavors, but because the techniques are proprietary, it is difficult to find specific studies in the scientific literature. The primary reasons for encapsulation are to prevent interactions with other nutrients, prevent losses due to oxidation or moisture, and to minimize undesirable flavors from vitamins or minerals. The type of coating or capsule used is dependent on the compound, and to a lesser extent, the matrix (Meyers, 1998). Vitamin C (ascorbic acid) is
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High-Energy, Nutrient-Dense Emergency Relief Food Product most often coated with fat or Ethocel to provide stability against oxidation. Vitamin K encapsulated in gum acacia is available on the market. Stable Nutrient Forms Stable nutrient forms, other than encapsulated, may also include metal chelates such as sodium iron EDTA (NaFe EDTA), which has been shown to be effective in reducing anemia, particularly in diets high in phytates, without adversely affecting other minerals (Davidsson et al., 1994, 1998; Hurrell et al., 2000). Iron chelates have been tested in various feeding situations and found to enhance absorption of soluble iron fortificants, such as ferrous sulfate or ferrous fumarate. For example, both NaFeEDTA and Na2EDTA were effective enhancers of iron absorption from cereal foods (Davidsson et al., 2001a, 2001b; Hurrell et al., 2000). Ascorbic acid had a similar effect in high-phytate foods (Davidsson et al., 2001a, 2001b; Hurrell et al., 2000). MICROBIOLOGICAL CONSIDERATIONS The addition of small amounts of solutes and dehydration are two main methods of decreasing aw and of increasing osmotic pressure in a food system to inhibit microbial growth. Reduced availability of water contributes to impaired microbial growth, and hence it has been used widely as a microbiological safety parameter (Beuchat, 1987; Gould, 1985; Lenovich, 1987; Troller, 1987; Troller and Christian, 1978). However, aw is not a universal parameter but rather an empirical one (Franks, 1982). The efficacy of manipulating aw is limited to certain types of microorganisms and is affected by food composition and environmental conditions (Andrews and Pitt, 1987; Corry, 1978; Vaamonde et al., 1982), and by the presence of microbial inhibitors (Leistner, 1995). Hence, there is no single minimum aw for inhibiting microbial growth that can be applied to all foods and all microorganisms. It is generally accepted that bacteria are more susceptible to osmotic effects than are molds and yeasts (with some exceptions). For IMF products, the main pathogenic bacterium of concern is Staphylococcus aureus, which can produce serious food poisoning if a significant amount of its enterotoxin is ingested. S. aureus, implicated in 20 to 40 percent of all foodborne illness outbreaks in the United States (Lavoie et al., 1997), is able to grow at an aw as low as 0.85. Additionally, yeasts and molds, particularly the xerophilic kind (those that prefer dry ambient conditions), survive and grow in moisture-limited environments. The lowest aw values at which mold growth may occur, albeit very slowly, are 0.61 to 0.62 (Pitt and Christian, 1968), whereas mold sporulation does not take place at aw less than 0.75 (Pitt, 1975). In addition to aw, factors influencing microbial survival and growth have been investigated with respect to water mobility, the translational or rotational
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High-Energy, Nutrient-Dense Emergency Relief Food Product motion of water molecules (Lavoie et al., 1997; Pham et al., 1999). It has been demonstrated that water mobility may influence transport of nutrients to microbial cells and hence growth. Under conditions of limited moisture, mold spore germination and mycelial growth strongly correlate with water mobility (Pham et al., 1999). For the EFP, the type and composition of ingredients used will influence the interaction of solids with water, thereby affecting water mobility and aw, and thus the survival and potential growth of pathogenic microorganisms. More importantly, should spores or vegetative cells of microorganisms able to withstand dry conditions survive the processing, they could germinate and grow during storage if moisture is not properly controlled in the product and other provisions, such as addition of preservatives, are not made to inhibit microbial growth. To minimize the risk of biological hazards, a multiple hurdle approach is highly recommended (Leistner, 1995). In this approach, also called the combined methods approach, several factors are used together to inhibit microbial growth, such as thermal processing, plus aw, storage temperature, preservatives, and packaging. For the EFP, it can be expected that there will be little, if any, opportunity to control storage temperature and ambient humidity. On the other hand, the cost of production and materials (including packaging) that would be incurred in making an IMF-type EFP might be too high, and there would also be a price to pay in terms of product shelf life and safety. As pointed out earlier, dehydration and IMF technologies can only stop microorganisms from growing but do not necessarily inactivate them. Consequently, and although an EFP having IMF characteristics should not be ruled out as an option, the optimal approach to the microbiological stability of the EFP would be a product design having an aw value lower than those in the IMF range (e.g., 0.4) and to add some preservatives. CHEMICAL STABILITY CONSIDERATIONS Lipid Oxidation Auto-oxidation of lipids occurs in foods largely via a self-propagating free radical mechanism. Since direct reaction of unsaturated linkages in lipids with oxygen is energetically difficult, production of the first few radicals needed to start the propagation reaction must occur through some catalytic mechanism (Nawar, 1996). It has been proposed that the initiation step may take place by decomposition to free radicals of preformed hydroperoxides via metal catalysis or heat, by exposure to light, by direct reaction of metals with oxidizable substrates, or by mechanisms where singlet oxygen is the active species involved (Nawar, 1996). Upon formation of sufficient free radicals, a chain reaction is initiated by the abstraction of hydrogen atoms at positions alpha to double bonds followed by oxygen attack at these locations. The result is production of peroxy radicals,
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High-Energy, Nutrient-Dense Emergency Relief Food Product Pallets Shippers will be assembled onto a pallet for transport. Pallets will be of construction and dimensions to provide efficient transport, with overhang and underhang restricted to a maximum of 2 in. Approximately 50 cases will be placed on a pallet. Pallets may be unitized using stretch wrap, banding, adhesive, or other means. Airdrop Naked Rations Depending upon the ultimate shape and density of the EFP, it should be possible to airdrop individual EFP packs in ways similar to MREs, using the Triad (tri-wall aerial distribution system) that was used to airdrop food in Bosnia (Roos, 1993). Individual MREs were found to fall with a terminal velocity of 58 mph, which was suitable for delivery. The tri-wall distribution container was used to transport the MREs, but was not included in the drop. This method may be applicable if the terminal velocity of the EFP is found to be sufficiently low to allow for safe delivery. However, given the caloric density requirements of the EFP, it is anticipated that it will be a heavy product such that additional packaging protection will be required for air delivery in this manner. Flutter Packs The World Food Programme developed a plastic film tube package with unequal amounts of food product sealed into each end. The length of tube between the product catches air during free fall and slows the descent. The unequal product weights cause a precessing (whirling) motion that absorbs energy during the free fall, thus the package name. However, because the weight of product delivered using this system is less than that of the EFP, its applicability for EFP delivery must be tested. Wing Packs Alternate configurations to the Flutter Pack may be developed that provide sufficient wind resistance to slow descent to a safe level. Bubble Packs Bubble packs or suitable cushioning material may be layered such that impact is attenuated as successive layers absorb impact and rupture. This would constitute an individual pack adaptation of the airbag approach that has been developed for bulk delivery (see below). Dimensions of bubbles, pressure of
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High-Energy, Nutrient-Dense Emergency Relief Food Product enclosed gas (which would change with altitude), and strength of substrate that will rupture must all be determined to prove efficacy for specific ration configurations (single or multiple) and specified drop heights. Drop height may be extended if terminal velocity is acceptable. Cushion Packs Additional cushioning materials may be employed to attenuate impact to acceptable levels for EFP delivery. These cushions could be composed of a variety of materials (thermoset or thermoplastic foams, rubber, cellulosic), composites, or constructions (such as paperboard honeycomb, mentioned below). Two considerations are required for suitability, however: the integrity of the EFP and the safety of the delivery. Unless remote delivery is assured, the airdrop must not present a hazard to the intended recipients. Bulk Drops Cushion The steady descent velocity experienced with parachute airdrops is about 28 ft/sec (Lee, 1992). Ground impact at this velocity requires an energy absorber to dissipate the impact energy. An evaluation of cushioning materials by Ellis and coworkers (1961) concluded that paperboard honeycomb was the most cost-effective, all-around, airdrop, energy-dissipating material. A majority of U.S. Army airdrops are delivered by the Container Delivery System, which has a 2,000-lb payload and uses honeycomb protection. Other cushioning materials may also prove adequate, but any material will require evaluation to assure proper loading and effectiveness under the environmental conditions that may be expected during the airdrops. Foam The U.S. Army evaluated alternatives to cushions because of specific shortcomings. Cushioning materials take up substantial warehouse space, are labor-intensive to use (primarily for equipment loads that require assembly, but would be less of a concern with uniform loads for items such as the EFP), and may degrade in high humidity (especially the paperboard honeycomb). Foams offers an alternative that overcomes these difficulties (Goldberg, 1990). As mentioned above, testing would be necessary to determine loading and use conditions. Air Bag Another option for airdrop impact reduction is air bags. This option utilizes the restricted venting of the air bag to reduce impact forces. Complex air bags
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High-Energy, Nutrient-Dense Emergency Relief Food Product using vent control and/or gas injection, and augmented air bags using paperboard honeycomb or other cushioning, have been found to improve the performance of simple air bags by decreasing peak gravity forces (Lee, 1992). Such systems offer further alternatives for bulk air drops of the EFP that could be evaluated when prototypes are prepared. COST CONSIDERATIONS The goal of this report is to develop an EFP that has an optimal nutritional profile and could meet the most severe environmental, storage, and logistic conditions. However, it is recognized that the requirements to produce such a sophisticated product are substantial. If funds are limited, a high unit cost can dramatically reduce the quantity of rations available to a needy population. Given this concern, the technical specifications recommended in this report should be considered optimal; however, the sponsoring agencies may choose to consider developing EFPs prepared and packaged to less stringent specifications if cost becomes a primary consideration. Under these circumstances, an EFP packaged in airtight foil bags inside a water-repellent paperboard box, for example, would allow greater quantities of products to be procured for a fixed cost and would be adequate in many relief situations, particularly for disaster relief. However, in this case, the long shelf-life objective and possibly also the goal of prepositioning supplies around the world would have to be modified by the agencies. REFERENCES Anderson AN. 1988. Typical causes of pinholes in pack rolled foil©. Lubr Eng 44:622–625. Andrews S, Pitt JI. 1987. Further studies on the water relationships of xerophilic fungi, including some halophiles. J Gen Microbiol 133:233–238. ASTM E-18 Committee. 1997. Proposed Standard Guide for Shelf Life Determination. Philadelphia: ASTM. Barnett RE, Kim H-J. 1997. Protein instability. In: Taub IA, Singh RP, eds. Food Storage Stability. Boca Raton, FL: CRC Press. Pp. 75–87. Beuchat LR. 1987. Influence of water activity on sporulation, germination, outgrowth, and toxin production. In: Rockland LB, Beuchat LR, eds. Water Activity: Theory and Applications to Food. New York: Marcel Dekker. Pp. 137–151. Bluestein PM, Labuza TP. 1988. Effects of moisture removal on nutrients. In: Karmas E, Harris RS, eds. Nutritional Evaluation of Food Processing. 3rd ed. New York: Van Nostrand Reinhold. Pp. 393–422. Bone D. 1973. Water activity in intermediate moisture foods. Developing shelf-stable formulations compatible with flavor, texture, and other aspects of food is a challenge to the food technologist. Food Technol 27:71–76.
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Representative terms from entire chapter: