Phenolic compounds profile and antioxidant capacity of 'Ataulfo' mango pulp processed by ohmic heating at moderate electric field strength.

Heat treatment during pasteurization of mango (Mangifera indica L.) pulp reduces the phenolic content and its potential health benefits. The bioactive content, phenolics profile, and antioxidant capacity of 'Ataulfo' mango pulp after ohmic heating (OH) treatment (15.0-20.0 V/cm), and conventional heating (CT, 72 °C) were evaluated. No significant differences were observed in the gallic acid and mangiferin content and its antioxidant capacity (ABTS). Mass spectrometry analysis (LC/MS-TOF) showed that all treatments produced the same profile of phenolic compounds, including 6 phenolic acids, 2 gallotannins, 1 benzophenone, 2 xanthones, and 3 flavonoids. PCA analysis confirmed that mangiferin and gallic acid were the main contributors to the ABTS antioxidant capacity. These results demonstrate that OH treatments can preserve the compositions of phenolic compounds mango pulp, thus maintaining its potential health benefits.

Heating-cooling extrusion cycles as a method to improve the physicochemical properties of extruded corn starch.

This work proposed a controlled method to modify the physicochemical properties of corn starch through heating and cooling extrusion (HCE) cycles. It was used native corn starch adjusted to 60% moisture. It was then subjected to 5 HCE cycles at 100 and 125 °C, at 10 rpm. Water absorption index (WAI), water solubility index (WSI), resistant starch (RS), thermal properties, viscosity, FTIR, and X-ray were evaluated. For WAI and WSI, a gradual increase was observed on each HCE cycle. Thermal properties shown that enthalpy decrease with each HCE cycles due to more gelatinization. Viscosity properties shown a thermally stable starch conditions being directly proportional to HCE cycles. The RS increased for each 5 HCE. XRD revealed that HCE cycle changed the starch structure from an orthorhombic structure to V-type crystalline structure. Finally, it was concluded that HCE cycles is a method to produce corn starch with controlled physicochemical properties.

Structural changes in popped sorghum starch and their impact on the rheological behavior.

Sorghum has been used to expand snacks such as pop sorghum. However, it is still unknown how the structural changes during the popping affect its rheological and functional properties. This study evaluated the structural changes of popped sorghum starch (PS) and their impact on rheological behavior. Moisture sorghum was adjusted to 11, 15, and 20% before popped. Morphology, X-ray pattern (XRP), infrared spectra (IR), thermal properties, and rheological behavior before and after popping were evaluated. Micrographs showed a honeycomb-like structure in PS. XRP showed partial damage to the orthorhombic crystals of the sorghum starch after PS, while the growth of crystalline lamellae was also generated (13.08 and 20.01°). IR showed structural damage as the signal at 1045 cm-1 disappeared in PS. The IM increased to gelatinization of the starch. The rheological behavior of PS displayed better thermal stability, with the lowest breakdown (25 ± 3.5 cP), setback (253 ± 11.3 cP), and final (1337 ± 5.7 cP) viscosity. The consistency coefficient k and flow behavior index n increase, meaning a loss of the pseudoplastic character. Viscoelastic properties increased in PS, suggesting the formation of cross-links and a stable matrix. Correlation analysis showed a strong relationship between structural changes and the rheological behavior of PS.

Impact of the popping process on the structural and thermal properties of sorghum grains (Sorghum bicolor L. Moench).

The popping process has been widely used as a technique for obtaining snacks. This study evaluated the effect of the popping process on the structural and thermal properties of sorghum. Seven varieties of sorghum were used. Raw sorghum grains were adjusted to 11% moisture and popped at 210 °C for 90 s with hot air. Microstructure, thermal and viscosity properties, and X-Ray and infrared spectrum were measured in raw and popped sorghum. The popping process produced an ordered honeycomb-like structure in the sorghum. The viscosity profile showed an increase in the thermal stability of popped sorghum. DSC measurements showed a starch gelatinization and a second transition about to 145 °C. XRD diffractograms display a reduction in the amplitude of the crystalline orthorhombic structure peaks. Finally, infrared indicated a change in the short-range structure and protein denaturation due to the popping process.

Effect of the nixtamalization process on the protein bioaccessibility of white and red sorghum flours during in vitro gastrointestinal digestion.

Protein bioaccessibility is a major concern in sorghum (Sorghum bicolor L. Moench) due to potential interactions with tannins affecting its nutritional value. Technological treatments such as boiling or alkaline cooking have been proposed to address this problem by reducing tannin-protein interactions. This research aimed to evaluate the impact of nixtamalization in the protein bioaccessibility from two sorghum varieties (red and white sorghum) during in vitro gastrointestinal digestion. Nixtamalization increased protein bioaccessibility in the non-digestible fraction (NDF) (5.26 and 26.31% for red and white sorghum, respectively). However, cooking showed a higher permeation speed of protein from red sorghum flours at the end of the intestinal incubation (9.42%). The SDS-PAGE profile of the digested fraction (DF) at 90 min of intestinal incubation indicated that, for red sorghum, cooking allows the formation of α and γ-kafirins while nixtamalization increase α-kafirin release. Principal Components Analysis (PCA) showed the association between nixtamalization and dissociation of δα kafirin complexes and increased protein content in the digestible fraction. In silico interactions indicated the highest biding energies for (+)-catechin and kafirin fractions (ß-kafirin: -7.0 kcal/mol; γ-kafirin: -5.8 kcal/mol, and δ-kafirin: -6.8 kcal/mol), suggesting a minor influence of depolymerized proanthocyanidin fractions with sorghum proteins as a result of the nixtamalization process. In conclusion, nixtamalization increased the bioaccessibility of sorghum proteins, depolymerizing condensed tannins, and breaking protein-tannin complexes. Such technological process improves the nutrimental value of sorghum, supporting its inclusion in the human diet.

Bioaccessibility and antioxidant activity of free phenolic compounds and oligosaccharides from corn (Zea mays L.) and common bean (Phaseolus vulgaris L.) chips during in vitro gastrointestinal digestion and simulated colonic fermentation.

Corn (Zea mays L.) and common beans (Phaseolus vulgaris L.) are alternative suitable ingredients for snacks, because of their content of bioactive compounds such as phenolic compounds (PC) and oligosaccharides (OS). However, there is no information about the transformation of these compounds associated with food matrix during gastrointestinal digestion. Therefore, the objective of this work was to simulate the whole digestion process (mouth to colon) to estimate bioaccessibility and small intestine permeability of free PC and OS, and the antioxidant capacity of free PC. Digested nixtamalized corn-cooked common bean chips exhibited significant different quantities of free PC and OS, and higher antioxidant activity compared to methanolic extract. The free PC showed high values of apparent permeability coefficients (0.023-0.729×10-3), related with their absorption in the small intestine. Both free PC and OS were retained in the non-digestible fraction of chips (10.24-64.4%) and were able to reach the colon. Our results suggest the digestion potential to increase chip bioactive compounds and antioxidant activity. Additional studies are required to evaluate their in vivo effects.

Wet method for measuring starch gelatinization temperature using electrical conductivity.

The objective of the present study was to develop a method for obtaining the gelatinization temperature of starches by using electrical conductivity. Native starches from corn, rice, potato, and wheat were prepared with different proportions of water and heated from room temperature to 90 degrees C, in a device especially designed for monitoring the electrical conductivity as a function of temperature. The results showed a linear trend of the electrical conductivity with the temperature until it reaches the onset gelatinization temperature. After that point, the electrical conductivity presented an increment or decrement depending on the water content in the sample and it was related to starch swelling and gelatinization phenomena. At the end gelatinization temperature, the conductivity becomes stable and linear, indicating that there are no more changes of phase. The starch gelatinization parameter, which was evaluated in the 4 types of starches using the electrical conductivity, was compared with those obtained by using differential scanning calorimeter (DSC). The onset temperature at which the electrical conductivity increased or decreased was found to be similar to that obtained by DSC. Also, the final temperature at which the electrical conductivity returned to linearity matched the end gelatinization temperature of the DSC. Further, a wet method for measuring the onset, peak, and end gelatinization temperatures as a function of temperature using the electrical conductivity curves is presented for a starch-water suspension.

Effect of lactic and citric acid on the stability of B-aflatoxins in extrusion-cooked sorghum.

AIMS: To evaluate the effect of the extrusion-cooking process with the addition of different acids concentration on the stability of B-aflatoxins in sorghum. METHODS AND RESULTS: Experimental units (EU) of sorghum flour contaminated with B-aflatoxins (140 ppb) were extrusion cooked with aqueous lactic or citric acid at six different concentrations. The effects of the two extrusion variables (moisture content and acid concentration) were analysed as a completely randomized factorial 3 x 6 design. Under some conditions, the aflatoxin reduction is more effective when using aqueous citric acid (up to 92%), than when using aqueous lactic acid (up to 67%). CONCLUSIONS: With citric acid, some extrusion treatments produced higher aflatoxin degradation rates, than those produced with lactic acid. SIGNIFICANCE AND IMPACT OF THE STUDY: Aflatoxin contamination is a great risk both for human as well as for animal health in underdeveloped countries; consequently, practical and economical detoxification procedures are needed that eliminate or at least minimize the aflatoxin risk, through lowering aflatoxin concentrations in grains. Under these considerations, extrusion process can be used for reduction in the aflatoxin content in contaminated grains.

Comparison of nixtamalization and extrusion processes for a reduction in aflatoxin content.

Traditional nixtamalization and an extrusion method for making the dough (masa) for corn tortillas that requires using lime and hydrogen peroxide were evaluated for the detoxification of aflatoxins. The traditional nixtamalization process reduced levels of aflatoxin B(1) (AFB(1)) by 94%, aflatoxin M(1) (AFM(1)) by 90% and aflatoxin B(1)-8,9-dihydrodiol (AFB(1)-dihydrodiol) by 93%. The extrusion process reduced levels of AFB(1) by 46%, AFM(1) by 20% and AFB(1)-dihydrodiol by 53%. Extrusion treatments with 0, 0.3 and 0.5% lime reduced AFB(1) levels by 46, 74 and 85%, respectively. The inactivation of AFB(1), AFM(1) and AFB(1)-dihydrodiol in the extrusion process using lime together with hydrogen peroxide showed higher elimination of AFB(1) than treatments with lime or hydrogen peroxide alone. The extrusion process with 0.3% lime and 1.5% hydrogen peroxide was the most effective process to detoxify aflatoxins in corn tortillas, but a high level of those reagents negatively affected the taste and aroma of the corn tortilla as compared with tortillas elaborated by the traditional nixtamalization process.

[Application of dielectric cooking in the elaboration of instant maize flour for the preparation of corn and tortilla chips]. / Aplicación de un proceso de cocimiento dieléctrico en la elaboración de harinas instantáneas de maíz amarillo para preparación de frituras de masa y tortillas.

This present work reports on the evaluation of a method for producing of instant flour for corn and tortilla chips based on dielectric cooking (DC). The samples prepared with lime showed a smaller variation in color than those without lime. A greater water absorption capacity was found in the samples processed without lime. The values for cohesion and adhesion of the DC masa prepared with lime are within the range of values previously reported for samples of masa prepared with nixtamal and commercial instant maize flours. The color analyses of chips from DC masa showed slight changes in relation to the chips prepared by the traditional process of nixtamalization. The DC tortilla chips (plus lime) with 15 minutes of DC showed similar values of delta E as compared to the control (commercial tortilla chips). The moisture of the DC chips varied in the range from 1.5 to 2.8. The DC tortilla chips with lime absorbed a lower amount of oil than the control sample and the corn chips. In fact, the DC chips absorbed lower amount of oil as compared to the control. The DC tortilla chips with lime and processed for 10 and 15 minutes were crunchy and smooth. Dielectric cooking displays a high potential for corn and tortilla chips with good functional characteristics, giving substantial savings of water, processing time and with higher yields due to the use of the whole grain.