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Occurrence of resistant starch in foodStarch, even as resistant as that of native potato, subjectedto thermal treatment in excess of water gelatinizes,thus becoming available to enzymes, and undergoes hydrolysis.It is, therefore, completely digested and assimilated bythe organism. Still, different technological treatments andfurther processing of carbohydrate products are likely toinduce the formation of some amounts of resistant starch inthose products.In different food products, a part of their starch is resistantto the activity of amylolytic enzymes. It depends on thebotanical origin of raw material and changes proceedingunder conditions of the production process. The content ofresistant starch in food fluctuates from a fraction up to 20%of product’s weight and is, to a high extent, determined byfood preparation manner [Brighenti et al., 1998]. During theproduction of bakery products and confectionery, the contentof resistant starch is observed to increase [Marlett &Longacre, 1996]. A further increase in RS content in bakeryproducts proceeds during their storage, mainly as a result ofamylopectin retrogradation [Eerlingen et al., 1994b]. Anincreased RS content in bakery products may be achievedby a change in technological parameters of the bakingprocess, and by the addition of high-amylose starch or lacticacid [Lijeberg et al., 1996]. The content of resistant starch indifferent cereal-based products depends on the raw materialused and technological process applied [Ranhotra et al.,1999]. The amount of resistant starch in rice, prepared forconsumption with different methods, is determined by theamylose concentration in starch [Sagum & Acrot, 2000]. Infried dry cereal products, resistant starch content dependson the botanical origin of starch used for their production.During frying, RS content increases, however the increase ishigher in the internal than in the external part of the friedproducts. In those products, resistance of RS starch to enzymaticactivity is positively correlated with amylose concentrationin starch used for their preparation. An increase inthe RS content in fried cereal products is accompanied bytheir increasing hardness [Pinthus et al., 1998].During thermal treatment of potato tubers, starch gelatinizesand is almost completely digested. Freshly-madepotato dishes contain 1–2% of resistant starch. However,the content of enzyme-resistant starch is observed toincrease substantially upon multiple cooling and heating ofthose products [Kingman & Englyst, 1994]. As a result ofcooked potato storage at a temperature approximating 0°Cmore resistant starch is formed than at room temperature[Gormley & Walshe, 1999]. Fried potato products, especiallyFrench fries, contain more resistant starch than cookedpotatoes. They are also characterized by a higher glycaemicindex compared to cooked potatoes [Garcia-Alonso &Go¼i, 2000]. The content of resistant starch in French friesincreases along with their increasing thickness. The starch ispacked non-uniformly, it occurs in smaller amounts in theouter layers of the French fries. Treatment of potato starchand potato amylose and amylopectin preparations accordingto procedures applied at the production of French friesindicates that amylose is responsible for the appearingresistance of starch. In this case, the resistance of potatoamylopectin is negligible [Go¼i et al., 1997]. In a variety ofproducts, including freeze-stored ones, the contents ofresistant starch increase depending on the origin of rawmaterial they are made of [Rosin et al., 2000].
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