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Reducing Food-Processing Costs in the 21st Century: Need for Innovative Separation Technologies H. S. Muralidhara* and Jagannadh Satyavolu† Cargill Central Research, P.O. Box 5699, Minneapolis, Minnesota 55440-5699
By the year 2000, the world population could reach 7 billion with 65-70% of this population in Asia and Africa. By 2005, 85% of the population growth is expected to be in Asia and Africa, the areas where food shortages are already most severe and the income levels are modest to low. Providing nutritional food to these developing parts of the world would require the use of separation technologies that will enable us to process food safely and economically, while reducing the energy and environmental costs associated with food processing. In this paper, the essential role of separation technologies to meet the food-processing demand of global population growth and the need for adapting these technologies to the developing parts of the world are discussed. The need for the discovery and development of novel materials for cost-effective and novel separation technologies is also addressed. Introduction
Table 1. Food Intake vs USDA Recommended Levels (Katz, 1998)
The common essential requirements for human survival are food, clothing, and shelter. While ample, highquality food is available in certain parts of the world, still about 800 million people suffer from malnutrition. The U.S. Department of Agriculture (USDA) conducts surveys of food intakes by individuals and compares the intake to the USDA recommended levels of food consumption. The food intakes were categorized into several basic food groups (Table 1). As shown in the table, the food intake falls below or at the most in the midrange of the USDA recommended levels. These deficiencies from recommended levels are more significant when we take the worldwide food intake into consideration. A food intake of below 1500 calories per day is considered malnutrition. It is estimated that there are about 800 million people in the world below this intake level. From 1975 to 1995, the global population went up by 42% to 5.7 billion (Figure 1). By the year 2000, the world population could reach 7 billion with 65-70% of this population in Asia and Africa. By 2005, 85% of the population growth is expected to be in Asia and Africa (Figure 2), - the areas where food shortages are already most severe. The shortage of food has many possible causes, most beyond the scope of this paper. However, expensive and inefficient processing of raw agricultural materials into food stuffs can contribute to the reduced availability of food. Food processing is well-developed in the U.S., Europe, and Japan; but the population growth and hence the need for increased agricultural products processing is in less developed countries. This, in turn, requires the food to be processed more efficiently, at a smaller scale, and at reduced costs. Food processors are addressing these dietary deficiencies by introducing new product formulations “designed to optimize intakes of key nutrients”. Further, with more and more people living longer, the aging population requires more nutritious foods or “designer foods”, * To whom correspondence should be addressed. E-mail: Hs•
[email protected]. Tel.: (612) 742-6402. † E-mail: Jagannadh•
[email protected]. Tel. (612) 742-6549.
basic food USDA recommended intake, men intake, women group level (servings/day) (servings/day) (servings/day) grains vegetables meat dairy fruits
6-11 3-5 5-7 (oz/day) 2-3 2-4
7.7 4.1 6.1 1.5 1.5
5.7 3.2 3.7 1.1 1.4
thus requiring new separation processes for new products. One example for designer foods is from milk processing. Using membrane separation for defatting, milk processors produce various grades of “low fat” milk. Similarly, “low lactose milk” is prepared by removing lactose from milk. As the world economy expands, the need and demand for processed food increases as well. For example, as the income level of people increases, their food consumption also increases. For people with low income, food is needed just for their survival. As people move into the mid-range of income, food variety and quality must be combined with both economy and nutrition. New facilities to process agricultural products for food and feed ingredients are being set up to cater to the changing needs of the population in various parts of the world. However, the cost of conventionally processing the agricultural products in the most needed parts of the world is too high because of the capital-intensive scale of conventional processing, lack of infrastructure, and
Figure 1. Consumers: how many? (Source: Agriculture Western Australia, Strategic plan 1996-2001.)
10.1021/ie990154r CCC: $18.00 © 1999 American Chemical Society Published on Web 08/26/1999
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Figure 2. Distribution of world population growth to 2005. (Source: Agriculture Western Australia, Strategic plan 1996-2001.) Table 2. Some Key Separation Unit Operations for Agricultural Products Processing •adsorption •centrifugation •chromatography •evaporation •extraction •filtration •flocculation/settling •flotation
•crystallization •distillation •drying •ion exchange •membrane processing
Table 3. Typical Composition of Foods (weight/100 g)a component
milk
water (g) 87.69 protein (g) 3.28 total lipid (fat) (g) 3.66 carbohydrate (g) 4.65 fiber - total dietary (g) ash (g) 0.72 - calcium (mg) 119.00 - iron (mg) 0.05 - phosphorus (mg) 93.00 - potassium (mg) 151.00 - sodium (mg) 48.80 vitamin C (mg) 1.47 vitamin B6 (mg) 0.04 vitamin E (mg) 0.10 a
soy flour, raw
beef
5.16 34.54 20.65 35.20 9.60 4.46 206.00 6.37 494.00 2515 13.00 0.00 0.46 1.95
58.10 28.11 3.84 5.71 0.00 4.24 11.00 2.70 168.00 429.00 1439.00 0.00 0.34 1.95
soybean oil butter 0.00 0.00 100.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 18.19
17.94 0.85 81.11 0.06 0.00 0.04 23.50 0.16 22.80 26.00 11.00 0.00 0.00 1.58
Source: USDA.
poorly developed markets. Separation technologies can play a key role in reducing the processing cost such that the processed food becomes affordable. There are several key separation technologies (unit operations) used in processing agricultural products (Table 2). Food is a complex mixture of components (see Table 3 for some examples) which may need to be separated or combined to achieve desired flavors, texture, or nutritional qualities. To process these complex food products at economical costs, we need to carefully evaluate and choose separation technologies or their combination. That can solve four kinds of issues (problems): (1) Geography. (2). Energy. (3) Water availability. (4) Environment.
Figure 3. Basis of separation.
These four issues are discussed in detail in the following sections. As will be described at the end of the next four sections, new materials are enabling new processing technologies that will further reduce foodprocessing costs. Any separation process is a balance or compromise among rate, yield, and selectivity (Figure 3). These three parameters dictate the cost of processing. New developed technologies could fall short of being commercialized because of a lack of the optimal balance among rate, yield, and selectivity. Selectivity is obtaining what we need from the rest of the process stream. The higher the concentration of the product (that we are trying to separate) in the feed stream, the cheaper it is to process (or separate) the product. The influence of product concentration in the feed stream on the final cost of the product is shown in Figure 4. As shown in the figure, the concentration of common products such as citric acid and amino acids is above 10 g/L of feed stream and the selling price of these products is within $1/kg. As the concentration in the starting feed falls below 1 g/L, the selling price shoots up to about $100/kg because of the high cost of isolating, purifying, and concentrating the product from the dilute feed stream. The rate is how fast or slow we can separate a particular product, which leads to the capital cost of the process. Since the availability of capital is limited, it is highly desirable
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Figure 5. Drying and evaporation in wet corn milling.
Figure 4. Product cost vs product concentration in the feed stream. (Source: Chem. Eng. News 1988, July 11.
to achieve high rates of separation. The yield is how much of the product we can separate and is dictated, among other factors, by thermodynamics. (1) Geography. Free trade is shifting the location of food processing. As barriers to trade fall, it is advantageous to process agricultural products close to customer markets. This allows the manufacturers to import raw materials, if needed, and process them to the various requirements (e.g., eating habits, taste, religious requirements, etc.) of the local population, while meeting the stringent international quality and health standards. These coupled with the type of raw material availability dictate the type and extent of separation technologies. Geography has a number of effects on the choice and combination of processing technologies. Locales with lakes and rivers may have abundant clean freshwater, permitting separations based on solution processes. Such processes may be uneconomical in arid zones. The availability of cheap energy for separation processes also depends on the geography. Geography also effects the transportability of the raw materials and products. The ease of transport (and high-capacity infrastructure) in the American central plains favor processes that operate at a very large scale. Such processes make little economic sense in locales where mountains or deserts restrict transport. Processes for such areas must be economic at a much smaller scale. The falling cost of long distance transport (especially ocean transport) combined with falling trade barriers and improved storage processes are reducing some of the impact of geography on processing choices. Moving processing from crop production areas to consuming areas allows processes to better match production to local requirements. This could obviously affect separation choices. (2) Energy. The food-processing industry is one of the largest energy-consuming industries. The total U. S. energy consumption is about 80-85 quads (1 quad
Figure 6. Concentration processes and energy requirements.
) 1015 BTU/year), while the food-processing industry consumes about 2 quads (at a cost of about $7.2 billion/ year). Within the food-processing industry, corn wet milling consumes about 94 trillion BTU/year and the vegetable oil processing industry consumes about 2 trillion BTU/year. Of all the major separation processes used in food processing, concentration and drying operations are the major consumers of energy (50% of the total energy consumption). For example, as shown in Figure 5, evaporation (concentration) and drying are the important unit operations in the corn milling industry. Thus, energy is a major part of the processing cost. Choosing energy-efficient separation processes for food processing is critical in reducing processing costs. Many breakthroughs have occurred in the development of new technologies to reduce the energy consumption for water removal during food processing. Figure 6 compares the energy requirements of various concentration processes. The energy availability depends to some extent on the geography. For examples, countries such as Canada have access to cheaper electricity (hydroelectric generation). Hence, electric-field-based technologies such as RF and UV drying, electrodialysis, etc. can be cost-effective. Certain rural parts of countries such as Bangladesh and India, where high levels of heavy metals were found in drinking water, cannot use the existing separation techniques for drinking water because of the high energy costs in those countries. Nontraditional energy sources such as solar and wind can be attractive for these parts of the world. (3) Water Availability. Water is the most common solvent used in processing agricultural raw materials into food ingredients. For example, the food industry in the U.S. uses about 210 billion gal/year of process water (Figure 7), about 10% of industrial water consumption. During food processing, water is added to
Ind. Eng. Chem. Res., Vol. 38, No. 10, 1999 3713 Table 4. Membrane Material Limitations
Figure 7. Process water consumption.
enhance component separation and transfer of the material through various process steps. However, at the end of the processing, the added water has to be removed for concentration and preservation (prevent spoilage and provide shelf life stability) of food. Thus, water adds to the high energy costs of the foodprocessing industry. Water quality is obviously critical to ensuring good final product quality. While water quality is currently not an issue in developed economies, it is a major uncertainty in many parts of the world. Sometimes, the first separation required in the process is to separate contaminants (both chemical and biological) from the process water to ensure food safety. Clearly, the processes used to purify water must be extremely inexpensive. This can also put a premium on the process that can make use of recycled water efficiently. Just as membrane-based processes reduce energy consumption, they also offset economic means of purifying and sanitizing input and recycled water streams. Process water availability and its quality are extremely important even beyond direct contact with the food material. Water is also used for all washing and sanitation steps of the process equipment. The effluent water from the food-processing plants has to be treated before disposal to meet discharge requirements. This normally requires treatment plants of high hydraulic loading. Thus, water as process water, its removal during concentration or drying, and its disposal significantly contribute to the overall cost of food processing. In addition, water can be an expensive utility in various parts of the world. Thus, separation technologies that use less water are needed to keep the processing cost down. New, cost-efficient separation technologies are also needed for the safe treatment of water for process use or safe discharge. (4) Environment. As described above, the processing of agricultural products for food requires significant amounts of energy and water for various process operations. In addition to the desired end products, food processing generates solid and liquid waste streams, heat, vapors, and possibly combustion gases. Local conditions and/or regulations may require all to be treated before release into the environment. The effluent streams from these processing plants typically contain huge solids, hydraulic and BOD loading adding significant capital and operating costs. In addition, with fermentation becoming a common process step, by-product carbon dioxide emissions are becoming alarmingly high. If the current trends in all process industries continue, then by the year 2050 the concentration of carbon dioxide in the atmosphere would be twice that of the preindustrial era, as predicted
during the Kyoto conference (Editorial comments from Science, 1997). If taxation based on carbon dioxide emissions prevails, then the cost of food processing and food products could rise considerably. Separation technologies that minimize energy use, water use (or maximize water recycling), and maximize by-stream utility can reduce food processing’s environmental impact. Thus, there is a dire need for energy-efficient technologies that offer environmental benefits while maintaining competitiveness. The Role of New Materials Throughout history, civilizations have been characterized by the development of “new” materials. The stone, bronze, and iron ages reflect the progress attributed to materials evolution. Similarly, the advances in our current information age can be attributed to “silicon”. It is our belief that although the basic principles of chemical engineering unit operations are wellestablished, any breakthrough in efficiency will occur as a result of the development of novel materials. Examples will appear in packaging, catalysts, membranes, adsorbents, and inert food contact material. Affinity separations, chiral separations, “membrane gates”, and certain microbes are examples of the technologies that can be made possible/more efficient with the development of novel materials. The novel materials used in these separation methods improve the selectivity of a process, thus reducing the need for elaborate downstream processing for the purification of a product. Yamaguchi et al. (1999) showed that a grafted polymer composed of N-isopropylacrylamide (NIPAM) and a copolymer can function as a membrane gate when fixed on to the surface of membrane pores. They showed that the membrane pores open and close depending on the ions in the aqueous solution, thus improving the selectivity of the membrane. The novel materials can also improve the rate of a particular process. For example, membrane separations are currently limited by the properties of the materials available for fabrications of the membranes and membrane modules. In aqueous applications, we require more hydrophilic membranes such as those made with regenerated cellulose (Table 4). However, the integrity (chemical and temperature resistance) of regenerated cellulose membranes is so poor that we use less hydrophilic (less desirable) polyethersulfone membranes in a majority of microfiltration applications. The low hydrophilicity leads to higher rate of fouling, lower throughputs, and hence a higher system cost. With suitably high hydrophilic membranes, we can reduce the system size and the associated capital and operating costs (Muralidhara and Satyavolu, 1998).
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Future Outlook The challenge of future separation technologies for processing agricultural products is that the technologies should be adaptable to the developing as well as developed world. The food processes, which are inherently high energy and water consuming, must be made economical and viable for the energy- and waterdeficient areas of the developing world without compromising food quality and safety. Separation technologies incorporating combined fields separation,2,3 (Muralidhara, 1988, 1994) hybrid processing, novel materials, and so forth can be used to reduce the processing costs. The innovation of novel materials will aid in the development of “enabling separation technologies”. Mini processing plants that can economically process smaller volumes may be attractive to these parts of the world. The development of scale-down designs rather than scale-up designs is quite important. Acknowledgment The authors thank Dr. Mike Porter of Cargill Central
Research for the review of the manuscript and Cargill Management for their support. Literature Cited (1) Katz, F. USDA Surveys Show What Americans Eat. Food Technol. 1998, 52 (11), 50-51. (2) Muralidhara, H. S. Combined Field Separations. ChemTech 1988, April, 229-234. (3) Muralidhara, H. S. Enhance Separations with Electricity. ChemTech, 1994, May, 36-41. (4) Muralidhara, H. S.; Satyavolu, J. Desired Membrane Features for the Year 2000: Industrial Users’ Perspective. Presented at the Tenth Annual Meeting of the North American Membrane Society, Cleveland, OH, May 16-18, 1998. (5) Editorial comments from Science 1997, 278 (12), 1691. (6) Yamaguchi, T.; Ito, T.; Sato, T.; Shinbo, T.; Nakao, S. Molecular Recognized Gating Membrane. Presented at ICOM ‘99, Toronto, Canada, June 12-18, 1999.
Received for review February 8, 1999 Revised manuscript received July 14, 1999 Accepted July 19, 1999 IE990154R
