Digestibility of Native and Modified Starches: In Vitro Studies with Human and Rabbit Pancreatic Amylases and In Vivo Studies in Rabbits

Abstract

The effects of cooking and chemical modification of purified starches on the relative rates and extent of their hydrolysis were studied in vitro by using purified human and rabbit pancreatic amylases. Comparison was made with an in vivo study of postprandial glucose and insulin response in adult rabbits. Uncooked starches showed negligible hydrolysis in vitro, whereas cooking (10 min, 100 degrees C) increased both the rate and extent of hydrolysis of all starches. Soluble potato starch was the most and potato amylose the least hydrolyzed. Unmodified tapioca and waxy corn starch were hydrolyzed at the same rate and to the same extent as soluble potato starches. In most cases chemical modification did not change the rate and extent of hydrolysis of the starches. Minor differences between human and rabbit pancreatic amylase exist, but there is a general resemblance between the two amylases in their starch-hydrolyzing properties (correlation coefficient = 0.90; P less than 0.001). The in vivo study showed that uncooked starches elicited no detectable glucose and insulin responses, whereas all the cooked starches except amylose caused glucose and insulin responses comparable to the response seen when feeding glucose. Chemically modified starches (especially waxy corn acetylated distarch adipate) seemed to promote a faster rate of absorption, but the total glucose response (i.e., for the entire 180-min duration) was similar for modified starches and their unmodified counter-parts. The in vivo results showed an overall qualitative similarity to the in vitro results but presented a quantitative difference in the magnitude of the responses for various starch preparations. A good correlation exists between the in vitro and in vivo results (correlation coefficient = 0.84; P less than 0.01). This indicates that the action of pancreatic amylases is an important determinant in the digestion and absorption of these carbohydrates.

Plasma glucose response and glycemic indices in pigs fed diets differing in in vitro hydrolysis indices

“…In particular, in vitro experiment involves the interaction of only the substrate and purified enzymes and the entire sample is incubated with an optimized cocktail at time 0 . In contrast, the in vivo digestion is a dynamic process that involves animal variation, chewing, bowel movement and other enzymes such as salivary amylases and glucose carriers Giuberti, Gallo and Masoero (Lee et al, 1985;Weurding et al, 2001;Hasjim et al, 2010). Moreover, the lack both in the simulation of the effect of diets on passage rate and viscosity and in the removal of digestion products foreseen for the in vitro analyses could further explain these differences (Weurding et al, 2001).…”

Digestibilidade aparente dos nutrientes de rações contendo diferentes fontes de fibra e níveis de amido com coelhos em crescimento

“…No entanto, fatores intrín-secos aos alimentos podem justificar as pequenas, mas significativas, diferenças observadas neste estudo, como, por exemplo, a encapsulação celular do endosperma, processo de moagem, resistência propiciada pelo conteúdo de água entre os polímeros de glicose, forma de distribuição da amilose no grão de milho, menor penetração de água e exposição do sítio de hidrólise da forma vítrea da amilose em relação à forma amorfa da amilopectina, a gelatinização do amido e sua posterior agregação com a parede celular e proteínas, além da reação de Maillard promovida pelo excesso de calor na peletização das rações, entre outros, que concorrem para diferenças na digestibilidade total da fração amilácea das rações (Lee et al, 1985;Rooney & Pflugfelder, 1986;Gidenne & Perez, 1993 a,b;Penz Jr., 1998;Arruda et al, 2000).…”

Digestibilidade aparente de dietas contendo diferentes níveis de amido para coelhos em crescimento

“…Adicionalmente, considerando-se a característi-ca do amido de cereais em possuir maior proporção de amilopectina que amilose (GREENWOOD, 1970) e o fato de as propriedades estruturais do grânulo de amido influenciarem a taxa de hidrólise pela amilase pancreática de coelhos (LEE et al, 1985; GIDENNE e PEREZ, 1993a), pressupõe-se que a maior proporção de amido de milho em relação ao milho grão pode ter sido determinante para a relativa eficiência diges-tiva observada neste estudo.…”