No abstract

People in the rural areas of Mexico consume corn tortillas and beans as basic components of their diet. However, little is known about the nutritionally relevant features of starch present in such combined meals. The objective of the present study was to evaluate the in vitro bioavailability of starch in tortilla-bean mixtures stored at 4 degrees C for different times, as compared to that of corn tortilla and boiled black beans kept separately under the same conditions. Available starch (AS), resistant starch (RS), and retrograded resistant starch (RRS) contents were measured. The in vitro starch hydrolysis indices (HI) of freshly cooked and cold-stored samples were evaluated using a chewing/dialysis digestion protocol. HIs were used to predict glycemic indices (pGI) of the samples. AS in tortilla and beans decreased between 3 and 6% after 48-72 h, whereas values in the mixture fell by 3% after 48 h, with no further change by 72 h. Only minor rises in RS contents (1.5-1.6%) were recorded for tortilla and beans after 72 h of storage, and a lower increase (0.4%) was recorded in the mixture. Judging from RRS values, an important proportion of RS is due to starch retrogradation. The HI and pGI were higher in tortilla than in bean and the mixture. Hydrolysis rate values decreased in the stored samples, a pattern that corresponded with RS and RRS changes. The slow digestion features of common beans are largely retained by the legume-tortilla combination. Data support the perceived health beneficial properties of starch in this traditional cereal-legume food.

Nixtamal, masa, and tortilla samples were stored for 24–96 hr and their chemical composition, retrogradation, and in vitro starch digestibility features were evaluated. Ash and fat contents in the three products were smaller than in the original corn sample, but protein levels were higher, all in accordance with previous studies. In general, a minor decrease in available starch (AS) content was observed with storage time. Masa showed the greatest AS values, followed by tortilla and nixtamal. Tortilla presented slightly higher retrograded resistant starch (RS3) values (1.1–1.8%, dmb) than masa (0.7–0.9%) and nixtamal (0.7–0.8%) and only minor increases were observed after 24 hr of storage, suggesting that retrogradation phenomenon in these samples takes place very rapidly and is more pronounced in the final product (tortilla). The development of RS3 explains the observed decrease in AS. Higher total resistant starch values were found in all samples at a range of 2.1–2.6% for nixtamal and masa, and a range of 3.1–3.9% in tortilla. This indicates that, apart from retrograded resistant starch, some ungelatinized fractions appear to contibute to the indigestible content of these products. The α‐amylolysis rate of the three materials decreased with storage. Tortilla showed the greatest hydrolysis indices. Differential scanning calorimetry (DSC) analysis showed that the nixtamal, masa, and tortilla did not show differences in amylopectin crystal melting temperature with storage time, but tortilla exhibited higher enthalpy values after 72 hr of storage, in accordance with the greater total RS contents recorded after prolonged storage.

Spaghetti developed by substituting semolina with 5, 10, 15, and 20% (w/w) banana starch were evaluated by specific physical and chemical parameters such as chemical composition, resistant starch (RS) content, diameter, bulk density, color, cooked weight, cooking loss, and firmness. They were also evaluated by their sensory attributes. In general, the addition of banana starch promoted a dilution effect on protein, lipid, and ash content, while moisture content was not affected. On the other hand, the content of RS significantly increased ( p50.05) with an increase of banana starch in the spaghetti. Spaghetti containing 5 and 10% of banana starch had similar diameter than the control spaghetti, but the diameter of spaghetti with 15 and 20% banana starch were significantly lower ( p50.05). The bulk density values of spaghetti with banana starch were all similar and not different from the control spaghetti. The values of ΔL* indicated that the color of spaghetti containing banana starch was darker than the control at all levels of substitution, while the values of ΔC* indicated that only spaghetti containing banana starch in the range of 10—20% was less saturated than the control. The evaluation of cooking quality demonstrated that the cooked weight of spaghetti containing banana starch was similar to the control, but their cooking loss was significantly higher and their firmness significantly lower ( p50.05) than the control. However, the values of cooking loss and firmness were in the acceptable range for good quality pasta. Sensory evaluation of the product showed that the addition of banana starch improved the acceptability of the spaghetti. The overall result of this study shows that spaghetti with up to 15% of banana starch addition could have great potential for commercial acceptability as a functional food with high levels of healthy RS.