Características físicas y químicas de dos razas de maíz azul: morfología del almidón

There are areas in Mexico, where local varieties of blue corn are grown (Zea mays L.), which have variability in size, density and grain hardness as well as chemical composition. Although these variables are defined by genetic factors, they also depend on farming practices, climatic conditions and soil type. The physical characteristics of corn grain are related to production and yield aspects, while its chemical composition and starch granules morphology, help to define the nutritional quality and its use in food processing. The objective of this study was to determine the physical and chemical properties of blue corn grain from two races and morphologically characterize the starch granules of the endosperm. The study was conducted at the Centre for Development of Biotic Products of the National Polytechnic Institute and the Valley of Mexico Experimental Station of the National Forestry, Agriculture and Livestock Research Institute. The samples were collected in the field with the producers, six Tabloncillo race materials at locations in Sinaloa and nine from Chalqueño race at Tlaxcala and Mexico State locations. Tabloncillo corn has small grains, higher hardness and damaged starch, and lowest levels of anthocyanins than Chalqueño corn has. The starch amount in both races was from 0.78 to 0.89 g g-1 of dry sample, and they are classified as normal because of their amylose content. The starch granules were spherical with smooth surface and a bimodal distribution (small granules were 2-8 ¿m and large granules were 16-18 um). The main differences between the two races were their grain size, floating rate and anthocyanin content.En México existen regiones donde se cultivan variedades criollas de maí­z azul (Zea mays L.), que poseen variabilidad de tamaño, densidad y dureza del grano, así­ como composición quí­mica. Estas variables si bien están definidas por el factor genético, también dependen de las prácticas de cultivo, condiciones climáticas y tipo de suelo. Las caracterí­sticas fí­sicas del grano de maí­z tienen relación con aspectos de producción y rendimiento, mientras que su composición quí­mica y la morfologí­a de los gránulos de almidón, ayudan a definir la calidad nutritiva y su uso en la elaboración de alimentos. El objetivo del trabajo fue determinar las propiedades fí­sicas y quí­micas del grano maí­z azul proveniente de dos razas, y caracterizar morfológicamente los gránulos del almidón de su endospermo. El trabajo se realizó en el Centro de Desarrollo de Productos Bióticos del Instituto Politécnico Nacional y en el Campo Experimental Valle de México del Instituto Nacional de Investigaciones Forestales Agrí­colas y Pecuarias. Las muestras fueron colectadas en campo con los productores, seis materiales de la raza Tabloncillo en localidades de Sinaloa y nueve de la raza Chalqueño en localidades de Tlaxcala y Estado de México. Los maí­ces de la raza Tabloncillo presentaron granos pequeños, mayor dureza y cantidad de almidón dañado, y menores contenidos de antocianinas, que la raza Chalqueño. La cantidad de almidón de ambas razas fue de 0.78-0.89 g g-1 de muestra seca, y por su contenido de amilosa se clasifican como almidones normales. Las formas de los gránulos de almidón fueron esféricas con superficie lisa y una distribución bimodal (gránulos pequeños 2-8 μm y grandes 16-18 μm). Las diferencias principales entre las dos razas fueron su tamaño de grano, í­ndice de flotación y contenido de antocianinas

Dietary fiber content, texture, and in vitro starch digestibility of different white bread crusts

Different types of white bread are sold and widely consumed worldwide. The objective of this study was to evaluate the starch digestibility in the crust of different white breads. Three popular commercial white breads were analyzed for dietary fiber (DF), thermal properties, texture, starch hydrolysis and resistant starch (RS) contents, in freshly baked and stored samples. The DF content in fresh crusts “as eaten” (6.8–7.2%) represents about 25% of the recommended daily consumption. The hardness and elasticity, RS and DF contents increased upon storage, associated with incomplete starch gelatinization and retrogradation, corroborated by the thermal analysis. The hydrolysis rate suggested that the structural arrangement of the starch components in the crust, possibly due to the low water content resulting from evaporation during baking and upon storage, restricts the susceptibility to digestive enzymes action. Consumption of bread crust may be suggested as a means to increase the DF intake

Unripe plantain flour as a dietary fiber source in gluten-free spaghetti with moderate glycemic index

Gluten-free products generally have low dietary fiber (DF) content. The aim of this study was to prepare a DF-rich gluten-free spaghetti and to evaluate the influence of the DF source on the chemical composition, cooking quality, texture, starch digestibility, and predicted glycemic index of the product. Unripe plantain flour (UPF) and Hi-Maize 260 were used as DF sources. The total DF in the uncooked samples was higher in the spaghetti with Hi-Maize 260 (17.4%) than in the UPF-containing one (9.6%), but no difference was observed between the two kinds of pastas (31%). Spaghetti with UPF showed shorter cooking time and lower cooking loss than the Hi-Maize 260-based sample. Microscopy observations revealed the presence of central zones containing ungelatinized starch granules. The predicted glycemic index of both spaghetti preparations was similar (66) and typical of medium GI products. UPF may be used as DF source in gluten-free pasta. Practical applications: Unripe plantain flour (UPF) is a source of indigestible carbohydrates (dietary fiber), including resistant starch. The consumption of starchy foods, like spaghetti, produce glucose peaks that are associated with the risk of cardiovascular diseases, obesity, and diabetes. Spaghetti with moderate glycemic index can be elaborate with the blend of other gluten-free flours as chickpea and maize. The study showed the factibility of UPF as source of dietary fiber in a gluten-free spaghetti at a lower cost than the commercial source (Hi-Maize 260)

Pregelatinised amaranth flour as an ingredient for low-fat gluten-free cakes

This work explored the use of pregelatinised amaranth flour (PAF) as an oil substitute in the preparation of amaranth cakes. Amaranth flour was extruded to achieve approximately 50% gelatinisation, ground and sieved. The PAF was used to replace the oil in the cake preparation at levels 33, 66% and 100%. FTIR analysis of the cake formulations showed that PAF modified the molecular organisation of starch and proteins. The starch showed more hydrated structures, although less ordered. The proteins exhibited a significant reduction in the β structures and a marked increase of the side chains, probably caused by the interaction with amaranth starch. The in vitro digestibility of starch showed a slight increase with the addition of PAF. The slowly digesting starch fraction showed a visible decrease, reflecting the presence of starch chains more accessible to amylolysis. Instrumental texture revealed an increase (P < 0.05) in cake hardness with the addition of PAF, particularly for medium (66%) and high (100%) oil replacements. Sensory analysis showed that the perceived texture, flavour and colour were negatively affected by the addition of the pregelatinised flour. Overall, the sensory analysis indicated that cakes with low levels of PAF oil replacement may be acceptable to consumers

Effect of oxidation and crosslinking on functional, rheological and thermal properties of oat and apple starches

Oat (Oa) and apple (Ap) starches were isolated and chemically modified by oxidation with 10% NaOCl to obtain oxidized starches (OOa and OAp), followed by cross-linking with a mixture of 5.6 g of sodium tripolyphosphate and 11 g of sodium trimetaphosphate to obtain doubly modified starches (OCOa and OCAp). In the native and modified starches, the functional properties (swelling power and solubility, and freeze-thaw stability) and thermal and rheological properties (steady-state flow curves and paste formation profile) were evaluated. The swelling power of native and double modified starches varied from 57 to 86 g/g and the solubility from 0.8 to 6.0 g/100 g, these variables increased as the study temperature increased; the increment in these properties was greater in Oa compared to Ap. Oxidation followed by crosslinking increased the freeze-thaw stability in Oa and Ap starches at 30, 60, 75, and 90 °C. It also increased the Tg of OCAp and OCOa ≈ 9% compared to the native samples, respectively; while an inverse pattern was observed in apparent viscosity were this value decreased ≈ 0.8 Pa × s for Oa and ≈ 0.5 Pa × s for Ap compared to the double modified samples. All samples presented a thinning cut-type behavior (pseudoplastic), indicating structural differences. Cross-linking in oxidized starches produced a reinforcing matrix that was determined in the paste formation profile. Dual modification (oxidation-cross-linking) could be an alternative for using starches from underused botanical sources, such as apples and oats, with different functional properties and feasible applications in food systems

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care