Twenty-five years ago, it was found that a significant fraction of the starch present in foods is not digested in the small intestine and continues to the large intestine, where it is fermented by the microbiota; this fraction was named resistant starch (RS). It was also reported that there is a fraction of starch that is slowly digested, sustaining a release of glucose in the small intestine. Later, health benefits were found to be associated with the consumption of this fraction, called slowly digestible starch (SDS). The authors declare both fractions to be "nutraceutical starch." An overview of the structure of both fractions (RS and SDS), as well as their nutraceutical characteristics, is presented with the objective of suggesting methods and processes that will increase both fractions in starchy foods and prevent diseases that are associated with the consumption of glycemic carbohydrates.

In the last century, starch present in foods was considered to be completely digested. However, during the 1980s, studies on starch digestion started to show that besides digestible starch, which could be rapidly or slowly hydrolysed, there was a variable fraction that resisted hydrolysis by digestive enzymes. That fraction was named resistant starch (RS) and it encompasses those forms of starch that are not accessible to human digestive enzymes but can be fermented by the colonic microbiota, producing short-chain fatty acids. RS has been classified into five types, depending on the mechanism governing its resistance to enzymatic hydrolysis. Early research on RS was focused on the methods to determine its content in foods and its physiological effects, including fermentability in the large intestine. Later on, due to the interest of the food industry, methods to increase the RS content of isolated starches were developed. Nowadays, the influence of RS on the gut microbiota is a relevant research topic owing to its potential health-related benefits. This review summarizes over 30 years of investigation on starch digestibility, its relationship with human health, the methods to produce RS and its impact on the microbiome. © 2018 Society of Chemical Industry.

Ultrasound technologies are increasingly used for the production of modified starches. An accurate understanding of the effects of ultrasound treatment on the morphological and functional properties of starch granules and dispersions is still under progress. This work studied the digestibility of corn starch as affected by ultrasound treatment (24 kHz). Results based on SEM, XRD, FTIR spectroscopy, and apparent viscosity analysis of native and sonicated starches were conducted to gain insights regarding the mechanisms affecting starch digestibility due to ultrasound treatment. The resistant starch content of native starch dispersions increased from 4.7 to 6.2% after 16 min of sonication. This increase was attributed to morphological and crystallinity changes that reduced the structure of the starch granule channels. For gelatinized starch dispersions sonicated 16 min, the resistant starch content increased from 2.1 to 4.0%, while the rapidly digestible starch fraction showed an increase from 42.9 to 60%, an affect that was attributed to the formation of short‐chained amylose molecules by effects of ultrasonic cavitation.

Summary The development of gluten‐free spaghetti with a low amount of glycaemic carbohydrate was investigated. The goal of this study was to determine the chemical composition, cooking quality and starch digestibility of gluten‐free spaghetti elaborated with mixtures of chickpea, unripe plantain and maize flours. The gluten‐free spaghetti presented a higher protein, fat and ash content than the control semolina spaghetti. The solid loss among all the gluten‐free spaghetti was in the range of 10.04–10.91% and not significantly different from each other. These values were almost at the limit of acceptability to be considered as good cooking quality. Total starch in the gluten‐free spaghetti was lower than the control spaghetti. The lower available starch (AS) and higher resistant starch contents in the gluten‐free spaghetti were associated with their lower rate of hydrolysis and predicted glycaemic index. There is a potential for developing gluten‐free spaghetti with reduced amount of glycaemic carbohydrates from unconventional food ingredients such as chickpea, unripe plantain and maize flours.

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