Resistant starch as functional ingredient: a review
parts special characteristics not otherwise attainable in high-fibre
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parts special characteristics not otherwise attainable in high-fibre foods ( Tharanathan & Mahadevamma, 2003 ). Some of the func- tional properties and advantages of commercial sources of RS2 and RS3 ( Nugent, 2005 ) are shown in Table 4 . They may also be used to provide fibre in some commercially available low-carbohydrate foods marketed for those following low-carbohydrate dieting regimens ( Nugent, 2005 ). There are also potential uses in fermented foods, such as dry-cured sausages. The processing conditions can affect the resistant content of starch by influencing its gelatinisation and retrogradation ( Thomp- son, 2000 ). Augustin, Sanguansri, and Htoon (2008) describe that it is possible to make a physically functional RS ingredient by the application of physical processes to starch suspension. Technically, it is possible to increase the RS content in foods by modifying the processing conditions such as pH, heating temperature and time, number of heating and cooling cycles, freezing, and drying ( Sajilata et al., 2006 ). The substitution of 3% milk solids in yoghurts (12% to- tal solids) with heated, sheared and microfluidised starch suspen- sions increased the viscosity and decreased syneresis of yoghurts but the incorporation of starch that had only been heated and sheared without microfluidisation did not. Unlike natural sources of RS (e.g. legumes, potatoes, bananas), commercially manufactured resistant starches are not affected by processing and storage conditions. For example, the amount of RS2 in green bananas decreases with increasing ripeness, while a commercial form of RS2, Hi-maize, does not present these difficul- ties ( Nugent, 2005 ). The food manufacture may be thought of as enhancement of the proportion of the starch that test as RS. The reason for including an ingredient high in RS is to combine physical functionality, process- ing stability and nutritional functionality. The physical functional- ity of RS is required for the physical characteristics of the food, such as texture, water-holding capacity. The processing stability of RS is important in order to preserve the nutritional functionality of the RS-containing ingredients. The nutritional functionality of the RS-containing ingredients can involve both resistance to diges- tion in the small intestine and resistance to fermentation in the co- lon. Eventually, we should be able to produce starch materials with the desired rate and extent of digestion (in terms of mean popula- tion responses) and (for any RS that might be present) a desired rate of hydrolysis and fermentation in the colon. In any starch material, the constituent molecules will have a range of susceptibility to amylolytic activity in vitro. For a starch or starch-containing ingredient, it is possible to alter this range by judicious selection of processing conditions to increase the pro- portion of RS. The starch material will also have a range of thermal stabilities before and after processing, which may or may not re- flect the range of susceptibility to hydrolysis ( Thompson, 2000 ). The industrial applications of RS mainly involve the preparation of moisture-free food products ( Yue & Waring, 1998 ). Bakery prod- ucts such as bread, muffins, and breakfast cereals can be prepared by using RS as a source of fibre. The amount of RS used to replace flour depends on the particular starch being used, the application, Table 4 Functional properties and advantages of commercial sources of RS2 and RS3. Sources: Sharma et al. (2008), Augustin, Sanguansri, and Htoon (2008), Sajilata et al. (2006), and Nugent (2005) . Natural sources Increase coating crispness of products Bland in flavor Increase bowl life of breakfast cereals White in color Functional food ingredients High gelatinization temperature Lowering the calorific value of foods Fine particle size (which causes less interference with texture) Lower water properties than traditional fibre products Useful in products for coeliacs as bulk laxatives and in products for oral rehydration therapy Good extrusion and film-forming qualities Allow the formation of low-bulk high-fibre products with improved texture, appearance, and mouth feel (such as better organoleptic qualities) compared with traditional high-fibre products E. Fuentes-Zaragoza et al. / Food Research International 43 (2010) 931–942 939 the desired fibre level, and, in some cases, the desired structure– function claims. The incorporation of RS in baked products, pasta products and beverages imparts improved textural properties and health bene- fits ( Premavalli, Roopa, & Bawa, 2006 ). A panel rated 40% TDF RS loaf cakes as best for flavor, grittiness moisture perception, and tenderness 24 h after baking. Based on an evaluation by a trained sensory panel of toasted waffles for initial crispness, crispness after 3 min, moistness and overall texture, RS waffle showed greater crispness than control or traditional fibre. RS can improve expan- sion in extruded cereals and snacks. RS may also be used in thick- ened, opaque health beverages in which insoluble fibre is desired. Insoluble fibres generally require suspension and add opacity to beverages. Compared with insoluble fibres, RS imparts a less gritty mouth feel and masks flavors less ( Sajilata et al., 2006 ). Bread con- taining 40% TDF RS had greater loaf volume and better cell struc- ture compared with traditional fibres tested ( Baghurst, Baghurst, & Record, 1996 ). Hydrolyzed starches (those which retain their granular struc- ture and essentially behave like unmodified starches in undergoing gelatinization on heating), which are also referred to as thin boiling starches, are also a form of RS. The advantage of this starch is the high concentration, which can be used as a paste of low viscosity, and its ability to set as a firm gel ( Seib & Kyungsoo, 1999 ). Cross- linked starches of RS4 type, based on maize, tapioca and potato, have been useful in formulations needing pulpy texture, smooth- ness, flowability, low pH storage, and high temperature storage ( Sajilata & Singhal, 2005 ). Baixauli, Salvador, Martinez-Cervera, and Fiszman (2008) stud- ied the instrumental texture characteristics of muffins with added resistant starch and noted that its addition produced a softer tex- ture: the samples were less hard, elastic and cohesive, reflecting a more tender structure; these effects were more evident at higher concentrations of resistant starch. Arimi, Duggan, O’Riordan, O’Sullivan, and Lyng (2008) have suc- cessfully replaced most or all of the fat in imitation cheese with resistant starch without adversely affecting meltability or hardness and conferring the well-established benefit of resistant starch as a functional fibre. In addition, low-fat, starch-containing imitation cheese has been demonstrated to have the potential to expand dur- ing microwave heating. Since this type of imitation cheese expands on microwave heating, it can be presented as a stand-alone snack, pre-expanded or as a home expansion product. 8. New sources of production There is considerable opportunity for future developments, especially for tailor-made starch derivatives with multiple modifi- cations, although the problem of obtaining legislative approval for the use of novel starch derivatives in processed food formulations is still under debate. Nevertheless, it can be predicted that new ventures in starch modifications and their diverse applications will continue to be of great interest in applied research ( Rudrapatnam & Tharanathan, 2005 ). More recent innovation has seen the development of insoluble, resistant maltodextrins with a functionality similar to that of resis- tant starches ( Buttriss & Stokes, 2008 ). Chemically-modified starch derivatives, for example, phosphor- ylated starches, which are also non-digestible, have been catego- rized as RS, similar to polydextrose or resistant oligosaccharides ( Rudrapatnam & Tharanathan, 2005 ). Esterification of native starch using citric acid resulted in chemically-modified starch with an RS content that depended on the degree of esterification. The produc- tion of this modified starch is relatively simple, and good results regarding the RS content can be achieved independent of the source of starch so that a range of RS-products can be produced, suitable for various foods. The results show that the RS content in toast bread could be increased by approximately 3%, when 7.5% citrate starch is added, compared to non-fortified bread ( Wepner et al., 1999 ). The use of citric acid for esterification seems to be evident as it rated as nutritionally harmless compared to other substances used for starch derivatisation ( Jyothi, Moorthy, Sreekumar, & Rajasekharan, 2007 ). Powdered preparations enriched in resistant starch (RS) have been obtained from native and lintnerized (prolonged acid treat- ment) banana starches by consecutive autoclaving/cooling treat- ments. The autoclaved samples had a higher RS content than their parental counterparts, but the chemical modification (lintner- ization process) allowed development of higher RS proportions (19%, dry matter basis). These RS-enriched products appear suit- able for the formulation of functional foods ( Aparicio-Saguilán et al., 2005 ). Bello-Pérez, González-Soto, Sánchez-Rivero, Gutiérrez-Meraza, and Vargas-Torres (2006) reported that extrusion can be used to elaborate products with a higher RS content that their native coun- terparts. The native starches of unripe banana and mango had a purity higher than 90%, with a 37% amylose content in banana starch and 27.5% in mango starch. No effect was observed in RS for- mation, which was 5.7% for banana starch (with more amylose) and 9.7% for mango starch. Reaction conditions were optimized to increase the content of resistant starch in adlay starch using esterification with glutaric acid, and the physicochemical properties of the prepared gluta- rate starches were investigated. Glutarate starches with lower crystallinity than raw starch had a similar RS content before and after heating with excess water. This glutarate starch could be used to enhance the textural properties and health benefits of low-moisture products, such as crackers and cookies, due to its low solubility and digestibility and heat stability ( Kim et al., 2008 ). Wheat bran starch isolated from commercial wheat brans using a wet-milling process was shown to have unique properties com- pared to commercial wheat endosperm starch. Starch recovery was 90% and the starch fraction contained a low level of protein (0.15%). The more resistant starch content and lower retrograda- tion rate are properties that present an opportunity to make wheat bran starch a new functional ingredient for the food industry ( Xie, Cui, Li, & Tsao, 2008 ). 9. Conclusion Fibre consumption has been reduced significantly in western society and is far below the recommended level. The main reason has been the change in life style, which has promoted a significant reduction in fruit, vegetables and legume consumption. With the aim of increasing fibre intake in the diet, many fibre-enriched foods have been developed. Resistant starch (RS) is a recently rec- ognized source of fibre and is classified as a fibre component with tải về 254.7 Kb. Chia sẻ với bạn bè của bạn:
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