Obtenção de amido resistente por intercruzamento e por tratamento hidrotérmico, e sua incorporação em bolos

• Autor(a) principal: Moraes, Jaqueline de [UNESP]
• Data de Publicação: 2016
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/138046
• topic: Resistant starch; Crosslinked starch; Digestibility; Structure; Amido resistente; Amido intercruzado; Digestibilidade; Estrutura

Resistant starch (RS) is defined as starch, or starch fraction, which is not digested in the gastrointestinal tract and can be fermented in the colon performing similar functional properties to those of dietary fiber. The RS application in bakery products can increase the fiber content of these foods without causing major changes in their sensory characteristics, requiring minor adjustments in formulation due to lower water absorption of RS compared to traditional fibers. In this work banana, cassava, corn and potato starches have been modified by heat moisture treatment (HMT), and crosslinking to obtain RS and then apply it in cakes. The HMT was conducted in starch conditioned at 18, 20 and 35% moisture using heating (130 °C), cooling (4 °C) and freezing (-18 °C) cycles. The starches were cross-linked using a mixture of sodium trimetaphosphate and sodium tripolyphosphate (99:1) at 45 °C for different times. The structural characteristics of native and modified starches were studied using X-ray diffraction, 31P nuclear magnetic resonance (31P NMR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Pasting properties, phosphorus content and digestibility of starches were also determined. The modification of starches by HMT resulted in low RS content, which didn’t exceed 2.57% in gelatinized starches for all conditions used. The RS content of cross-linked starches increased reaching 88.66, 65.40, 60.08 and 43.56% for potato starch, cassava, banana and corn, respectively, with acceptable phosphorous content. The higher treatment time resulted in higher levels of phosphorus, reduction in starch rapidly digestible starch (RDS) and slowly digestible starch (LDS) contents and increase the RS content of all starches. However, starches of different botanical sources show different behavior during phosphorylation and different RS contents. The gelatinization temperature of crosslinked starches had small changes compared to native starches, but the crosslinked starches no showed viscosity peak when analyzed by Rapid Visco Analyzer, indicating the formation of covalent bonds which result in a rigid granular structure. The X-ray diffraction patterns did not change with crosslinking, although the relative crystallinity decreased in banana, potato and cassava starches and increased in corn starch. The inclusion of phosphate groups during the crosslinking, which initially occurs in the amorphous region of the granule, promotes swelling in this region and results in change in the crystalline region. The formation of different phosphate esters was observed in 31P NMR spectras, that showed great influence on digestibility of starch. Among such esters are the monostarch monophosphate (MSMP) distarch monophosphate (DSMP), monostarch diphosphate (MSDP) and the cyclic monostarch monophosphate (cyclic MSMP), which alter the digestibility by hindering access of enzymes due to the volume of the formed structures (MSMP, MSDP and cyclical MSMP) or by cross-link the chains (MSDP). The steric hindrance promoted by the inclusion of phosphate groups may be strongly related to the increase in the RS content of starches. The incorporated phosphorus content was found to have less influence than that the way the phosphorous is linked in the starch molecules to reduce enzymatic digestibility. The addition of RS in cakes resulted in products with higher volume, greater crumb clarity, and lower retrogradation, but the fiber content was lower than that for the cakes can be considered as a source of fiber.