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FOOD TECHNOLOGY INTELLIGENCE INC. |
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SOME ARTICLES RECENTLY PUBLISHED IN
Emerging Food R&D ReportApril 2006VOL 17, IS 1 Emerging Food R&D Report (ISSN 1050-2688) is published monthly. © 2006 by Food Technology Intelligence, Inc., 215 Godwin Ave., P.O. Box 322, Midland Park, NJ 07432-0322 USA; phone 201-445-4227; fax 201-447-5904; email ftiinfo@ftipub.com. Visit our website at www.ftipub.com. Fee: one year, $365; two years, $630. Add $20 per year for service outside North America. TABLE OF CONTENTS (Click on title to go to story)
In this report… Evaluating processing aids that inhibit the production of aldehyde and analyzing secondary compounds could help fruit growers and processors deliver products that would better satisfy consumers. Read what can be done to optimize mixing equipment, water temperature and shear rate to improve the quality of a beverage and its acceptance by consumers. It is generally recognized that the color of orange juice is a quality that is noticed by the consumer. See what can be done to improve the color of this beverage and make it more appealing. Control the formation of secondary flavor compounds Most volatile flavor compounds are esters, alcohols, aldehydes, ketones, lactones and sulfur-containing compounds. Aldehydes are generally formed enzymatically or oxidatively and are seldom considered endogenous in intact fruit. Lipoxygenase catalyzes the formation of such aldehydes as hexanal, (E)-2-hexenal, (E,Z)-2,6-nonadienal and (E)-2-nonenal. These compounds, although not considered endogenous to fruit, are known to be important in how they impact flavor in the tomato and cucumber. The induction or presence of secondary volatiles in stored processed fruits might affect the products’ flavor attributes. The goal of USDA-ARS scientists was to compare endogenous and secondary aldehyde production in cantaloupe, honeydew, mango and watermelon by sampling unprocessed tissue and fruit blended using different protocols. Investigators used a lipoxygenase inhibitor, n-propyl gallate (nPG), and oxygen exclusion technology. Various techniques were used to isolate and identify target compounds. In cantaloupe and honeydew, scientists recovered esters, alcohols and aldehydes. They found a few aldehydes present in cantaloupe, mango or watermelon tissue. The use of oxygen exclusion and nPG techniques had similar results in blocking the formation of most aldehydes during cantaloupe sampling. Levels of hexanal, (E,Z)-2,6-nonadienal and (E)-2-nonenal were reduced 89%, 97% and 94%, respectively, in nPG-blended honeydew. In mango, mostly terpenes were recovered. However, hexanal and (E,Z)-2,6-nonadienal were also recovered and were completely inhibited by nPG blending. In watermelon, the researchers recovered aldehydes, alcohols and ketones. Levels of hexanal, (E)-2-hexenal and (E)-2-nonenal were reduced by 90%, 68%, and 95%, respectively, when blended with nPG. Lipoxygenase-generated compounds were present in the blended samples. Their levels were reduced substantially by inhibitors. These compounds are believed to have a significant impact on the flavor and aroma attributes of these fruits. Like tomato and cucumber, the researchers’ data indicate that some flavor-important secondary compounds are not formed until fruit is macerated or its tissue disrupted. Evaluating processing aids that inhibit aldehyde production, and analyzing secondary compounds after fruit is processed and during its fresh-cut fruit storage, could help the industry deliver products that would better satisfy consumers. Further information. Jeanne Lea, Food Processing and Sensory Quality Unit, USDA-ARS Southern Regional Research Center, 1100 Robert E. Lee Blvd., New Orleans, LA 70179; phone: 225-342-5812; email: jlea@srrc.ars.usda.gov. High-shear blending optimizes dairy-based beverage The quality of a beverage is often directly correlated to the size of the particles of which it is composed. Larger particles will precipitate faster. Research indicates that mixing equipment, water temperature and shear rate all affect the size of the particles, and thus directly contribute to the quality of the beverage, and how well it is accepted by consumers. Scientists at Kansas State University wanted to determine the best mixing conditions that would lead to the smallest casein size, the least sedimentation and the least foam production of reconstituted nonfat dry milk (NFDM). The researchers examined the impact of a range of variables, including high-shear blending and recirculation equipment, water temperatures of 4 C and 22 C, and high- and low-shear rates. They found that the mixing approach that would best improve the shelf life of dairy-based beverages appears to be high-shear blending at 22 C. The investigators reconstituted NFDM with distilled deionized water to 11% w/v at 4 C for all treatments. A randomized block design was used with four replications. Particle size was measured on a commercial laser scattering particle size distribution analyzer on the day of mixing. The researchers monitored sedimentation for seven days after mixing. Foam volume and stability were measured for two hours after mixing as well. High-shear blending at 22 C produced the smallest casein size—0.155 µm—without any sedimentation, but a moderate amount of stable foam. Overall, higher shear rates resulted in smaller casein sizes (2%) than the lower shear rates did after mixing. NFDM reconstituted at 4 C had larger casein sizes (3.6%) than NFDM reconstituted at 22 C. The investigators did not see any sedimentation for any treatment. Foam stability was the greatest when using high-shear blending at 22 C. Foams produced using the recirculation method were low in volume and unstable. Further information. Karen Schmidt, Food Science Institute, Department of Animal Sciences and Industry, Kansas State University, 224 Call Hall, Manhattan, KS 66506; phone: 785-532-1216; email: kschmidt@ksu.edu. Optimize the color of orange juice It is generally recognized that the color of orange juice is a quality that is noticed by the consumer. The most natural way of improving the color of orange juice is to add other juices, which provide a more intense coloration. For instance, U.S. legislation allows for the addition of up to 10% of mandarin juice to orange juice to improve its color. Researchers in Spain compared the color characteristics of juices from 11 mandarin cultivars currently being grown in Spain. Experimental results indicated that only the green-red coordinate, a*, of the orange juices can be improved by adding mandarin juice. The mandarin cultivar that provided a juice with the highest value of a* was the Clementine. Once this selection was made, investigators studied the impact of adding mandarin juice at different ratios, up to 10%, on the color characteristics of orange juice. Values of the a* coordinate went from 5.50 for pure orange juice to 6.29 for a mixture of 90% orange juice plus 10% of mandarin juice. Hedonic tests proved that regular juice consumers preferred the color of mandarin juice to that of orange juice. They liked the color of the juice mixture containing 10% mandarin juice better than that containing 3% mandarin juice. Making orange juice more attractive to consumers is helpful. The benefits of orange juice are many. Orange juice naturally contains more than 60 phytonutrients, many of them flavonoids. Scientists believe these plant-derived components are intimately involved in fighting cellular damage, a common pathway for cancer, aging and a variety of diseases. According to recent USDA surveys, the average calcium intake for young women and men is below the recommended amounts. The average calcium intake by women 20 to 29 years of age is about 778 milligrams per day, and the average calcium intake by men 20 to 29 years of age is 1075 milligrams. Approximately 25% of women over the age of 50 suffer from osteoporosis caused by not consuming enough calcium and other bone-healthy nutrients on a daily basis. Further information. Angel A. Carbonell-Barrachina, Departamento Tecnología Agroalimentaria, Universidad Miguel Hernández, Carretera de Beniel, km 3.2, 03312 Orihuela, Alicante, Spain; phone:+34-966749754; fax: +34-966749677; email: angel.carbonell@umh.es. Investigate oxidative stability of phytosterols Phytosterols are plant-derived compounds that are similar in structure and function to cholesterol. Although early human diets were rich in phyotosterols, as much as 1 g per day, the typical Western diet currently is relatively low in phytosterol content. Phytosterols inhibit the intestinal absorption of cholesterol. Numerous clinical trials have demonstrated that consuming foods, on a daily basis, that are enriched with at least 0.8 g of plant sterols or stanols lowers serum LDL cholesterol. The oxidative stability of phytosterols as lipid compounds can be defined as their resistance to oxidation. Phytosterol oxidation products (oxyphytosterols) may be formed during the processing and storage of foods. Researchers in Finland studied the oxidative stability of phytosterols that occur during the processing and long-term storage of phytosterol-enriched milk powder and heat-treated milk, and in microcrystalline phytosterol suspensions in different fats and oils. All of these products were stable, in spite of the heat treatments used in their processing and long-term storage, even at slightly elevated temperatures. The largest change in the phytosterol oxide content was found in phytosterol-enriched milk powder that had been stored at 38 C for 12 months. During this period, the amount of phytosterol oxidation grew from 0.03% to 0.07%. The investigators concluded that the formation of phytosterol oxides did not seem to be a limiting factor for the manufacture and subsequent storage of the food products they tested. Some epidemiological studies have found that a higher intake of plant foods containing phytosterols is associated with a decreased risk of cancer. But it is not clear whether phytosterols or other compounds in plant foods are the protective sources. Further information. Vieno Piironen, Department of Applied Chemistry and Microbiology, University of Helsinki, Latokartanonkaari 11, P.O. Box 27, 00014, Helsinki, Finland; phone: +358-9-19158228; fax: +358-9-19158475; email: vieno.piironen@helsinki.fi. Rice-based batter cuts oil absorption by half Many calorie-counting dieters have had to cut back on their consumption of deep-fried foods. But such foods might now be acceptable as an occasional indulgence, if the fried favorite is made with a fat-fighting rice-flour batter. Typically, fried drumsticks, crispy fries, or glistening donuts are loaded with oil and fat that can contribute to obesity and heart disease. But USDA-ARS chemists have formulated a rice-based batter as an alternative coating for fried foods. When compared to traditional wheat-based batters, the new rice mixture reduces oil absorption by more than half. Investigators selected rice because rice is plentiful, and flours and starches made from it are among the least likely to cause food allergies. By using rice, scientists also take advantage of a basic scientific fact: oil and water don’t readily mix. Because of rice’s ability to retain water, it’s better able to repel oil. About four years ago, researchers tested their rice flour mixture on chicken breasts and nuggets. The new batter absorbed 60% less oil than one made with wheat. More recently, the researchers wanted to see how veggies dipped in the rice-flour mixture fared when plunged into hot oil. In contrast to animal products, like chicken and fish, which are also commonly deep-fried, vegetables are fat-free. Batters are responsible for soaking up most of the oil and fat when vegetables are battered and fried. How this oil uptake occurs in foods that are battered compared with those that aren’t is what interests the scientists. The vegetable they turned to for their study was a natural choice: fried okra, a culinary favorite across the southern United States. When dipped in the rice-based coating, the okra absorbed 50% less oil than when coated with a traditional wheat batter. But what will fried okra fans think of this new, slimmed-down version? Investigators asked volunteers to evaluate the less oily, more heart-healthy okra. The panelists reported that the okra made with the rice batter was just as crispy and tasty as traditionally battered and fried okra. Some even found its rich, golden-brown color to be superior to wheat-batter okra. The rice batter still awaits commercialization. Further information. Frederick Shih, USDA-ARS Southern Regional Research Center, Room 127, S. Campus Dr., Food Science Building, Louisiana State University, Baton Rouge, LA, 70803; phone: 225-278-2599; email: fshih@srrc.ars.usda.gov. Interparticle interactions and gelation impact structure, rheology You already know that most foods are composed of a network of small particles and large molecules that are held together by various intermolecular and colloidal forces. A food’s structure, texture and stability are significantly influenced by the strength of these interactions, especially protein-protein and protein-lipid interactions. Foods are generally in a metastable state. Their texture depends on the structural changes that occur as they’re processed. Researchers at the U.K.’s University of Leeds wanted to better understand the relationship between a product’s texture and its processing history. They used a combination of computer simulations and lab experiments on model systems to relate the structure and rheology of aggregated networks of milk protein particles to the interparticle interactions and conditions that control the gelation process. The effort included undertaking a computer simulation of particle gelation; examining structure using various image analysis techniques; investigating the rheology of various gels and emulsion droplets; and studying protein-lipid interactions. Investigators made substantial progress in relating the structure and rheology of simulated particle gels to the nature of interparticle interactions. Simulations of monodisperse systems demonstrated the effect of an energy barrier on the kinetics of aggregation and the fractal character of the aggregated network structure. The simulations also showed the effect of bonding strength and non-bonded interactions on the pore-size distributions and rheological behavior at small and large deformations. By comparing simulation and microscopy studies, researchers established the dependence of the structure of aggregated particle systems on the nature of interparticle interactions and polydispersity. Small-deformation and large-deformation rheological properties of simulated aggregated particle networks successfully reproduced the mechanical properties of some real milk protein gels, emulsion gels and adsorbed protein layers. Scientists closely correlated the rheological properties of emulsions, emulsion gels and protein-lipid interactions inferred from interfacial studies. The scientists continue to work in this area. Their other research efforts include investigating the structure and dynamics of milk proteins at fluid interfaces, the c reaming, flocculation and rheology of emulsions, and the interactions of surfactants and biopolymers in food colloids. Further information. Eric Dickinson, University of Leeds, Department of Food Science, Leeds LS2 9JT, England, U.K.; phone: +44 113 233 2956; fax: +44 113 233 2982; email: e.dickinson@leeds.ac.uk. Investigate alternative processes for fruit, vegetables USDA-ARS scientists are working to develop new processing technologies that could improve the quality and safety of processed fruits and vegetables while at the same time reducing their production costs. The ultimate goal of this effort is to create alternative technologies that produce blanched, dehydrated, partially-dehydrated or infused or coated fruits and vegetables, as well as restructured fruits and vegetable products. Investigators would like to achieve their objective by using a combination of infrared dry-blanching (IDB), freezing, freeze-drying, air-drying, dipping or infusion coating or related technologies. The new technologies would be used to make processed products that have a better texture and nutritional quality. The processes would lower production costs and reduce microbial loads compared to current technologies. The end result: novel cereals, snacks and other applications. Fresh or frozen fruits and vegetable whole products and purees are being used for this research. The sliced or restructured fruits and vegetables may be dipped in antioxidant solutions to prevent discoloration before any thermal processing steps are undertaken. Researchers will test and evaluate how infusing or coating flavors, humectants, nutrients and phytochemicals at various processing stages will affect product quality and processing characteristics. Specifically, the infusion or coating media to be studied will include fruit puree, calcium, sugars, sugar polyols and high fructose corn syrup. Scientists will determine the influence of blanching and dehydration on product quality and processing characteristics by using IDB and heated air prior to freezing or freeze drying product. When evaluating product quality, scientists will examine texture and sensory characteristics, such as density and crunchiness, appearance, color, flavor, the hydration rate in skim and full-fat milks, water activities, enzyme inactivation and microbial safety. The processing and energy efficiencies will be determined for various production regimes. The effects of design parameters on product quality and energy efficiency will also be studied. The research is scheduled to run through February 2008. Further information. Tara Mchugh, Processed Foods Research, USDA-ARS Western Regional Research Center, 800 Buchanan St., Albany, CA 94710; phone: 510-559-5864; fax: 510-559-5851; email: thm@pw.usda.gov. New wheat targets low-glycemic foods Scientists with Australia’s CSIRO have developed an experimental wheat that could provide benefits in the areas of bowel health, diabetes and obesity. In a paper published in the international science journal, Proceedings of the National Academy of Sciences, researchers working within CSIRO’s Food Futures Flagship describe how they used CSIRO-developed RNAi gene-silencing techniques to suppress the expression of two starch-branching enzymes in an experimental wheat. “The wheat had a significantly altered starch composition, increasing the amount of amylose from about 25% to 70%,” Dr. Matthew Morell says. “Amylose is a form of starch that is more resistant to digestion, providing the potential for the new wheat to be an important component of foods with a low glycemic index. Starch resistant to digestion is expected to generate favorable changes in the gastrointestinal tract that promote bowel health and would be expected to lead to a reduction in colorectal cancer risk.” An animal trial confirmed positive changes in indicators of bowel health in rats fed a diet of the high-amylose wheat, when compared to standard wheat. Importantly, there was no change in the growth rate of the rats. “The use of gene technology has proved exceptionally useful in defining the genetic changes in wheat that are required to generate this new type of wheat,” says Morell. The research team’s current task is to breed the wheat using conventional methods, instead of gene technology. By using molecular marker technology investigators are able to identify the genetic diversity needed for developing high-amylose wheats by conventional breeding. Researchers and colleagues also are developing novel wheat varieties to meet emerging health needs. Diet-related non-infectious diseases, such as colorectal cancer, heart disease and diabetes, are some of the most serious health problems in the developed world. They are major causes of premature death and disability, and pose a serious economic and social burden. These new wheats produce significant levels of resistant starch. They can be incorporated as wholegrain into breads, cereals and other foods, giving us the opportunity to improve our health. The paper, titled “High-amylose wheat generated by RNA interference improves indices of large-bowel health in rats,” appears in the Feb. 27, 2006 edition of the Proceedings of the National Academy of Sciences. Further information. Matthew Morell,Senior Principal Research Scientist, CSIRO Plant Industry, G.P.O. Box 1600, Canberra ACT 2601, Australia; phone: +61 2 6246 5074; fax: +61 2 6246 5000; email: Matthew.Morell@csiro.au. Convert lactose to galactooligosaccharide and optimize intestinal health Food fermentation processes rely on both endogenous and microbial enzymes to degrade starches, lipids, proteins, anti-nutritional and toxic substances. In some cases, microbial enzymes associated with indigenous fermentation processes exhibit unusual properties. Microorganisms are the primary source of many industrial enzymes. About 50% of them originate from fungi and yeast, 35% from bacteria, and 15% are either of plant or animal origin. Microbial lactase can hydrolyze lactose in milk into glucose and galactose. It is used to address the problem of lactose intolerance, which is prevalent in a number of developing countries. Researchers at Agriculture and Agri-Food Canada have developed and want to commercialize a technique that produces several natural thermostable and cold-temperature active lactases from GRAS microorganisms grown in cheese whey. Investigators grew GRAS microorganisms in waste cheese whey. The enzymes were released by homogenization and were partially purified. The lactases actively hydrolyzed lactose and synthesized oligosaccharides at different temperatures. Some of these enzymes were overproduced by cloning lactases genes in Escherichia coli using different plasmid vectors. They were purified using salt fractionation and chromatography techniques. Lactase of Streptococcus thermophilus was overproduced more than 1000-fold in E. coli by harnessing recombinant DNA technology. Using some of these lactases, up to 50% of concentrated lactose in whey permeate was converted into galactooligosaccharides as bifidogenic factors and nutraceutical products. Dietary oligosaccharides, which can be fermented by intestinal bacteria, are beneficial for intestinal health. The scientists want to collaborate with an industrial partner to conduct pilot tests and bring the research to the pre-industrial stage. The industrial partner will need some specific equipment for the production of native and recombinant lactases: a fermentor, homogenizer or sonicator, and a centrifuge. The study of recombinant lactases also requires chromatography equipment. Galactooligosaccharides are a mixture of oligosaccharides consisting of D-glucose and D-galactose. They are produced from D-lactose via the action of the enzyme beta-galactosidase obtained from Aspergillus oryzae . Galactooligosaccharides are not usually digested in the small intestine. They are fermented by colonic bacteria. This could lead to changes in the colonic ecosystem in favor of some bacteria, such as bifidobacteria, which may have health benefits, including protection against certain cancers and lowering of cholesterol levels. Further information.Steve Bittner, Commercialization and Business Development, Agriculture and Agri-Food Canada Food Research and Development Centre, 3600 Casavant Blvd. W., St. Hyacinthe, Quebec J2S 8E3, Canada; phone: 450-773-1105; fax: 450-773-8461; URL: http://res2.agr.gc.ca. Scientists are trying to determine the role of the consumption of fish in preventing the development of colorectal cancers. They also want to learn if it matters whether the fish is oily. Researchers have known for some time that epidemiological studies examining fish intake and omega-3 fatty acid intake give inconsistent results. However, laboratory-based studies suggest that omega-3 fatty acids, such as those found in oil-rich fish, should help to prevent colorectal cancers. These studies do not support a protective role for the omega-3 fatty acids sourced from plants in relation to cancer prevention. The problem with epidemiological studies is that they are often based on questionnaire data on food intake, which may only have few questions relating to fish intake. The omega-3 content of fish can vary widely, and this is not easily accounted for in these types of studies. Also, few of the studies separate the fish and plant sources of omega-3. To overcome these limitations, some scientists would like to undertake intervention studies. Researchers believe it is important to look at whole foods at levels that can be fairly easily integrated into the diet, and this is why they are undertaking the current research. Contact: Elizabeth Lund, Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, England, U.K. Phone: +44 1603 255000. Fax: +44 1603 507723. Email: liz.lund@bbsrc.ac.uk. |
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