Summary
Extrusion cooking, as a multi-step, multi-functional and thermal/mechanical process, has permitted a large number of food applications. Effects of extrusion cooking on nutritional quality are ambiguous. Beneficial effects include destruction of antinutritional factors, gelatinisation of starch, increased soluble dietary fibre and reduction of lipid oxidation. On the other hand, Maillard reactions between protein and sugars reduce the nutritional value of the protein, depending on the raw material types, their composition and process conditions. Heat-labile vitamins may be lost to varying extents. Changes in proteins and amino acid profile, carbohydrates, dietary fibre, vitamins, mineral content and some non-nutrient healthful components of food may be either beneficial or deleterious. The present paper reviews the mechanisms underlying these changes, as well as the influence of process variables and feed characteristics. Mild extrusion conditions (high moisture content, low residence time, low temperature) improve the nutritional quality, while high extrusion temperatures (200 °C), low moisture contents (<15%) and/or improper formulation (e.g. presence of high-reactive sugars) can impair nutritional quality adversely. To obtain a nutritionally balanced extruded product, careful control of process parameters is essential.

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Nutritional aspects of food extrusion: a review

Potentially toxic acrylamide is largely derived from heat-induced reactions between the amino group of the free amino acid asparagine and carbonyl groups of glucose and fructose in cereals, potatoes, and other plant-derived foods. This overview surveys and consolidates the following dietary aspects of acrylamide: distribution in food originating from different sources; consumption by diverse populations; reduction of the acrylamide content in the diet; and suppression of adverse effects in vivo. Methods to reduce adverse effects of dietary acrylamide include (a) selecting potato, cereal, and other plant varieties for dietary use that contain low levels of the acrylamide precursors, namely, asparagine and glucose; (b) removing precursors before processing; (c) using the enzyme asparaginase to hydrolyze asparagine to aspartic acid; (d) selecting processing conditions (pH, temperature, time, processing and storage atmosphere) that minimize acrylamide formation; (e) adding food ingredients (acidulants, amino acids, antioxidants, nonreducing carbohydrates, chitosan, garlic compounds, protein hydrolysates, proteins, metal salts) that have been reported to prevent acrylamide formation; (f) removing/trapping acrylamide after it is formed with the aid of chromatography, evaporation, polymerization, or reaction with other food ingredients; and (g) reducing in vivo toxicity. Research needs are suggested that may further facilitate reducing the acrylamide burden of the diet. Researchers are challenged to (a) apply the available methods and to minimize the acrylamide content of the diet without adversely affecting the nutritional quality, safety, and sensory attributes, including color and flavor, while maintaining consumer acceptance; and (b) educate commercial and home food processors and the public about available approaches to mitigating undesirable effects of dietary acrylamide.

Review of methods for the reduction of dietary content and toxicity of acrylamide.

Acrylamide in cereal products: A review

Optical based sensing systems that measure luminescence, fluorescence, reflectance and absorbance, etc., are some of the areas of applications of optical immunosensors. Immunological methods rely on specific binding of an antibody (monoclonal, polyclonal or engineered) to an antigen. Detection of specific microorganisms and microbial toxins requires immobilization of specific antibodies onto a given transducer that can produce signal upon attachment of typical microbe/microbial toxins. Inherent features of immunosensors such as specificity, sensitivity, speed, ease and on-site analysis can be made use for various applications. Safety of food and environment has been a major concern of food technologists and health scientists in recent years. There exists a strong need for rapid and sensitive detection of different components of foods and beverages along with the food borne and water borne pathogens, toxins and pesticide residues with high specificity. Biosensors present attractive, efficient alternative techniques by providing quick and reliable performances. There is a very good potential for application of biosensors for monitoring food quality and safety in food and bioprocessing industries in India.

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Biosensors in food processing

Sweet potato, green beans, Tommy Atkins mango, and blue potato were fried in a vacuum frying process at a temperature of 120e130 � 1 � C. Before frying, green beans and mango slices were soaked in a 50% maltodextrine 0.15% citric acid solution. The products were also fried in a traditional (atmospheric pressure) fryer at 160e165 � 1 � C for 4 min. A 30-member consumer panel rated the sensory quality of both types of fried snacks using a 1e9 hedonic scale. Compared with traditional frying, oil content of vacuum-fried sweet-potato chips and green beans was 24% and 16% lower, respectively. Blue potato and mango chips had 6% and 5% more oil, respectively, than the traditional-fried samples. Anthocyanin (mg/100 g d.b.) of vacuum-fried blue potato chips was 60% higher. Final total carotenoids (mg/g d.b.) were higher by 18% for green beans, 19% for mango chips, and by 51% for sweet-potato chips. Sensory panelists overwhelmingly preferred (p < 0.05) the vacuum-fried products for color, texture, taste, and overall quality. Most of the products retained or accentuated their original colors when fried under vacuum. The traditional-fried products showed excessive darkening and scorching. These results support the applicability of vacuum frying technology to provide high-quality fruit and vegetable snacks.

Vacuum frying of high-quality fruit and vegetable-based snacks

Potatoes and other foods that have a high content of the amino acid asparagine and a high accumu- lation of reducing sugars are subject to the formation of acrylamide upon frying. The objectives of this research were (1) to analyze the level of acrylamide formed during deep-fat frying of potato chips and (2) to evaluate means of reducing acrylamide in potato chips by using different potato cultivars and vacuum frying. Several potato cultivars were used in this research, including Innovator (I), NDTX 4930-5W (N), ATX 854 04-8W (ATw), Atlantic (A), Shepody (S), ATX847806-2Ru (ATr), and White-Rose ( W) . An electric bench-top (atmospheric conditions)-type fryer was used to fry the potatoes. Three temperatures were used: 150 °C, 165 °C, and 180 °C. The vacuum frying experiments were performed at 118 °C, 125 °C, and 140 °C and a vacuum pressure of 10 Torr. The potatoes were sliced (1.5-mm thick) and fried for different lengths of times. For potatoes fried at 165 °C (for 4 min) at atmospheric conditions, the acrylamide contents were 5021 55 ppb (W), 552 25 ppb (I), 358 50 ppb (N), 397 25 ppb (ATw), 646 55 ppb (A), 466 15 ppb(S), and 537 14 ppb (ATr). Vacuum frying reduced acrylamide formation by 94%. Results showed that both cultivar and modified frying systems can play an impor- tant role in reducing acrylamide formation in fried potatoes. As the frying temperature decreased from 180 °C to 165 °C, acrylamide content in potato chips reduced by 51% during traditional frying and by 63% as the tempera- ture decreased from 140 °C to 125 °C in vacuum frying. Increased frying time increased acrylamide formation during traditional frying for all temperatures and frying methods analyzed. However, the effect on acrylamide

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S.E. Tichy

Papers

Reduction of Acrylamide Formation in Potato Chips by Low-temperature Vacuum Frying