Resistant starch derived from processed legumes—purification and structural characterization

Resistant Starches and Non-Communicable Disease: A Focus on Mediterranean Diet

Resistant starch (RS) is the starch fraction that eludes digestion in the small intestine. RS is classified into five subtypes (RS1-RS5), some of which occur naturally in plant-derived foods, whereas the others may be produced by several processing conditions. The different RS subtypes are widely found in processed foods, but their physiological effects depend on their structural characteristics. In the present study, foods, nutrition and biochemistry are summarized in order to assess the type and content of RS in foods belonging to the Mediterranean Diet (MeD). Then, the benefits of RS consumption on health are discussed, focusing on their capability to enhance glycemic control. RS enters the large bowel intestine, where it is fermented by the microbiome leading to the synthesis of short-chain fatty acids as major end products, which in turn have systemic health effects besides the in situ one. It is hoped that this review will help to understand the pros of RS consumption as an ingredient of MeD food. Consequently, new future research directions could be explored for developing advanced dietary strategies to prevent non-communicable diseases, including colon cancer.

Structural, functional and digestibility characteristics of sorghum and corn starch extrudates (RS3) as affected by cold storage time

The aim of the study was to compare the properties of resistant starch (RS₃) formed during extrusion of corn and sorghum starches. The extrudates were stored for 7 and 14 days at 4 °C to allow for molecular rearrangement i.e. retrogradation. The extruded starches were analyzed for enzymatic digestibility, long range (X-ray diffraction, XRD) and short range (FTIR) molecular order, thermal characteristics (DSC) and rheological properties as affected by temperature. The highest RS (70.64%) was obtained for sorghum extrudate (ES₁₄) as compared to corn extrudate (EC₁₄) (64.90%), on 14th day of storage. The increase in RS correlates with the increase in percent crystallinity (%Xc), too. The (ES₁₄) reported the highest %Xc among all extrudates i.e.37.83. The XRD results showed an additional peak at 13° and 20°, reflecting the formation of V-type pattern in all samples. The FTIR spectroscopy also exhibited increase in the ratio of 1047 cm^-1/1151 cm^-1 and 1047 cm^-1/1022 cm^-1. The extruded starch showed significantly higher thermal stability and lower cold paste viscosity. The significant (p ≤ 0.05) decrease in the glycemic index was obtained as the storage time increased. The (ES₁₄) exhibited glycemic index equal to (EC₁₄) i.e.55.53 and 52.53, respectively; thereby making it a suitable substitute of corn starch.

Comparative study on the chemical composition, anthocyanins, tocopherols and carotenoids of selected legumes

Twenty-nine legumes were assessed for their nutritional and phytochemical compositions. Soybean and black soybean had the highest protein contents (34.05-42.65 g/100 g DW, dry weight of legumes), particularly being a rich source of lysine (1.78-2.23 g/100 g DW. Soybean and black soybean had the highest fat contents (14.13-22.19 g/100 g DW). Broad beans had the highest unsaturated fatty acids (83.57-89.01 g/100 g fatty acid), particularly rich in α-linolenic and linoleic acid. The highest and the lowest dietary fiber were found in red kidney beans (35.36 g/100 g DW) and mung beans (22.77 g/100 g DW), respectively. Except for soybean and white kidney bean, 6 major anthocyanins in the legumes samples were identified. The soybean contained the highest total tocopherols content (90.40-120.96 μg/g dry weight of beans), followed by black soybean (66.13-100.76 μg/g DW). The highest carotenoids were found in lentils (4.53-21.34 μg/g DW) and red kidney beans (8.29-20.95 μg/g DW).

Changes in molecular structure of chickpea starch during processing treatments: A thin layer chromatography study

To detect the changes in molecular structure of chickpea starch during processing treatments, a thin layer chromatographic method for characterizing the molecular structure of chickpea starch was developed. With this method, the components in chickpea starch could be divided into amylopectin, small linear molecules and large linear molecules, and their contents could be determined. It was found that the degrees of polymerization of the large linear molecules and small linear molecules in chickpea enzyme-resistant starch were about 40 and below 15, respectively. Furthermore, the small linear molecules were more susceptible to α-amylase hydrolysis than the large linear molecules. The results suggested that the large linear molecules and small linear molecules in chickpea enzyme-resistant starch might mainly originate from the amylose and amylopectin of native chickpea starch, respectively, based on the retrogradation properties of amylose and amylopectin and the enzymatic degradation behavior of the large linear molecules and small linear molecules.

Studies on effect of multiple heating/cooling cycles on the resistant starch formation in cereals, legumes and tubers

'Resistant starch' (RS) is defined as starch and starch degradation products that resist the action of amylolytic enzymes. The effect of multiple heating/cooling treatments on the RS content of legumes, cereals and tubers was studied. The mean RS contents of the freshly cooked legumes, cereals and tubers (4.18%, 1.86% and 1.51% dry matter basis, respectively) increased to 8.16%, 3.25% and 2.51%, respectively, after three heating/cooling cycles (P< or =0.05) with a maximum increase of 114.8% in pea and a minimum of 62.1% in sweet potato (P< or =0.05). Significant positive correlations were observed between the RS content and amylose (y=0.443x-5.993, r=0.829, P< or =0.05, n=9) as well as between the percentage increase in RS and insoluble dietary fiber content (y=2.149x-24.787, r=0.962, P< or =0.05, n=9). A differential scanning calorimeter study showed an increase in the T(0), T(p), T(c) and DeltaH values of the repeatedly autoclaved/cooled starches. The intact granular structure was also observed disappear, as studied using scanning electron microscopy.