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Amylose is well known to be organized helically with six glucose per turn, allowing it to form complexes with various ligands. This interaction can be affected by the type of crystalline structure present in the starch sources. This study evaluated the effect of extrusion on the crystalline structure of starch during RS5 formation. Rice and potato starches were extruded at 100 °C and 15 rpm with 5% and 10% oleic acid (OA), then the physical, thermal, paste properties, and resistant starch content (RS) were evaluated. Potato starch extruded with 10% OA showed granules embedded in a gelatinized starch matrix. The X-ray revealed that rice (orthorhombic) and potato (hexagonal) structures remain unchanged even after extrusion. Differential scanning calorimetry (DSC) evidenced the formation of type IIa amylose-lipid complexes in OA treatments, where potato extruded with 10% OA had the highest enthalpy (0.9 J/g). Moreover, the extruded potato showed the highest pasting temperature (87.19 °C), supporting the complex formation. The RS was reduced from 15.8 (isolated) to 4.14 mg/100 mg (extruded 10% OA) in rice. For potato, RS decreased from 17 to 13 mg/100 mg (isolated and extruded 10% OA). Overall, these findings suggest a tendency in potato starch (ortho-rhombic) to interact with OA during the extrusion process, promoting a crystalline lamellae growth when extruded with 10% OA, therefore, changing their properties.

The use of pectin from coffee mucilage (PI) is an alternative to reduce the environmental impact of the wet processing coffee industries by applying it in the generation of degradable films. Hence, the aim of this work was to valorize industrial coffee waste as a source of pectin to prepare biodegradable films by a novel methodology (electrospraying), perform chemical characterization of pectin, and compare the films with a control method (casting) and pectin (citric, PC). Coffee mucilage pectin composition (PI) was different, having smaller galacturonic acid content (52.2%) than PC. The presence of neutral sugars (ribose, xylose, glucose), the high degree of esterification (84.92 ± 1.70) and the diffractogram and Raman spectra results, gave the basis to consider PI as a high methoxyl pectin. PI films showed different physical properties and structure than Pc, depending on the composition and method of production. Regarding mechanical and barrier characteristics, films prepared with pectin from coffee mucilage presented a typical behavior of rigid polymers; they were also more permeable to water vapor (2.91 ± 0.02 × 10−12 g/s m Pa) and were highly biodegradable and soluble in water. Due to these characteristics, the production of films from coffee mucilage pectin becomes a suitable alternative to give added value to this unexploited waste.

The aim of this study was to evaluate the effect of acid hydrolysis and succination upon single and a combination of both of them as a dual modification on the morphological, structural, thermal, and pasting profile of the achira starch in order to expand its potential food applications. The surface of achira starch granules was eroded with acid hydrolysis, while the succination resulted in the formation of pores or cavities, having a slight impact on the crystallinity and the gelatinization enthalpy. Succinated starch presented the lowest transition temperatures (To = 60.29 °C, Tp = 65.03 °C and Te = 69.86 °C) compared to other starches in this study. The succination increased the final viscosity (3808 cp) when compared with the native starch (3114 cp), while acid hydrolysis resulted in a decreased value (735 cp). These are desirable properties for its possible use as an additive in bakery industry processes.

The use of particles obtained from biopolymers is of interest in fields such as bioengineering and nanotechnology, with applications in drug encapsulation, tissue engineering, and edible biofilms. A method used to obtain these particles is electrohydrodynamic atomization (EHDA), which can generate different structures depending on the process conditions and raw materials used, opening a wide range of research in the biopolymers field, where starch is considered an excellent material to produce edible and biodegradable films. This chapter is a compilation and analysis of the newest studies of this technique, using starch with or without modifications to prepare films or membranes and their potential applications. A systematic literature review, focused on starch, and EHDA was carried out, finding 158 articles that match these criteria. From these results, a search inside them, using the words edible and biodegradable was conducted, showing 93 articles with these key words. The information was analyzed observing the preference to use corn, potato, rice, and cassava starches, obtaining mainly scaffolds and fibers and, in much less proportion, films or capsules. This review shows a window of opportunity for the study of starchy materials by EHDA to produce films, coatings, and capsules at micro or nano levels.

Pulque is a Mexican alcoholic, probiotic beverage with shelf life of 3 days. The physicochemical, probiotic, and sensory properties of pulque depend on its content of lactic acid bacteria (LAB) and yeasts. The aim of this study was to apply ohmic heating (OH) in order to extend the shelf life of pulque without altering its properties. Pulque processed by conventional pasteurization (63 °C, 30 min) was used as control. Parameters such as electrical conductivity (0.22 S/m) and optimal pasteurization conditions by OH (65 °C, 5 and 7 min; 70 °C, 3 and 5 min) were determined. Shelf life was evaluated with these parameters during 22 days of storage at 4 ± 1 °C. A higher content of LAB (6.68 and 5.96 log10 CFU/mL) was obtained at 65 °C for 5 and 7 min, respectively, compared with conventional pasteurization (3.54 log10 CFU/mL). After 22 days, physicochemical properties (pH, color, and alcohol content) were stable for both methods of pasteurization. However, the pulque treated with OH had greater sensory acceptance. For the first time, OH was used to process pulque, and results revealed that is an effective technology for extending the shelf life until 22 days, preserving microbiological and physicochemical properties. Microorganisms as surviving the OH treatments were identified as Lactobacillus acidophilus, Lactobacillus kefiri, and Saccharomyces cerevisiae.

We studied the changes in the phytochemicals profile of two instant corn flours produced by different process: traditional nixtamalization process (TN) and by ohmic heating process (OH). The highest total phenolics content was found in the OH flours (OHF), which showed predominance of bound phenolics and free flavonoids compared with the TN flours (TNF). Ferulic acid measured by HPLC-DAD was the most abundant compound in its bound form in the OHF, but decreased by 57% in TNF. The insoluble fiber content was preserved by the OHF (17.49%) and the soluble fiber increased ∼65% compared with TNF. These data suggest that instant corn flours processed by OH preserves the phenolic profile and antioxidant profile similarly than flours processed by TN; furthermore, water waste was reduced significantly, and no effluents were produced in the ohmic heating process.

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.

Black garlic (BG) is obtained by the Maillard reaction under controlled conditions of temperature and humidity. This study describes the traditional processing (TT-BG) and the use of ohmic heating (OH) as pre-treatment (OH-BG) to improve time processing. Physicochemical composition and sensory properties were of particular interest in this study. The OH as a pretreatment causes the hydrolysis of fructans to fructose, which are degraded during storage under traditional treatment conditions (70 °C/94% RH) through the Maillard reaction causing the faster formation of compounds responsible for the color of black garlic compared to black garlic without pre-treatment. This reaction cuts down the time to attain the characteristic color of black garlic from 30 to 12 days. The 5-hydroxymethyl-2-furaldehyde (HMF) content was 3.6 times higher in OH-BG than in TT-BG. The polyphenol content and antioxidant capacity did not show differences between TT-BG and OH-BG, but their levels were superior to commercial sample. Both products (OH-BG and TT-BG) were sweet (36.8 and 31.6 °Bx, respectively) and had an excellent organoleptic acceptance (75 and 70%). These results highlight the potential of ohmic heating pretreatment in reducing the time to obtain good quality BG., Ríos-Ríos was supported by a scholarship from the Consejo Nacional de Ciencia y Tecnología (CONACYT-Mexico).

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., Author A. H. Cabrera-Ramírez was supported by a scholarship from the CONACYT-Mexico, grant number: 734975. This work was supported by Instituto Politécnico Nacional, grant numbers SIP-20196083, SIP-20200568.

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., Authors F.G. Castro-Campos and A.H. Cabrera-Ramírez thanks the “Consejo Nacional de Ciencia y Tecnología” (CONACYT-Mexico) for the financial support of their post-graduate position [Grant numbers: 712859 and 734975, respectively]. This research was supported by the FOPER-2018 and 2019 of the Universidad Autónoma de Querétaro.

The nutritional, cooking and technological properties of the Tepary bean (TB) cultivated in Mexican northeast comparing to two common beans varieties (Pinto Americano and Black Jamapa) were evaluated in this study. Nutritional parameters evaluated of TB resulted significantly different from common beans varieties analysed, except lipid fraction. Cooking times of soaked (4 and 8 h) and non-soaked varieties varied significantly; TB shows between 55.1–80.49 min by cooking time. The textural profile analysis (TPA) of TB showed a significant reduction of hardness, chewiness and adhesiveness in soaked compared to non-soaked. In addition, TB presented a similar behaviour to Pinto Americano in TPA non-soaked and cooked and soaked 8h and cooked, except to adhesiveness. Technological properties of TB and resistant and non-resistant starch content showed significant differences between species. Due to, TB has nutritional, cooking and technological properties comparable to other edible legumes as common bean, mainly Pinto Americano variety.

Commercially, crab meat is obtained by hand-picking after a cooking process, followed by pasteurizing or canning. Jumbo lump is one of the pieces of meat obtained from the blue crab. The aim of this study was to evaluate the effect of the commercial cooking process (boiling and steaming) on the mechanical and functional properties of whole jumbo lump and the gels obtained from cooked and minced jumbo lump from blue crab (Callinectes sapidus). The gels were prepared combining the washing process and microbial transglutaminase. The boiling and steaming processes showed a different effect on the textural and color properties. Whole jumbo lump pieces cooked by immersion in boiling water showed a higher hardness value as compared to steamed jumbo lump pieces, suggesting a different internal structural. The cooking processes used in this study did not modify the water holding capacity, gelling capability, or color of the minced jumbo lump. The addition of microbial transglutaminase to washed minced jumb...

In this study, achira (Canna edulis) starch (AS), a non-conventional starch, was hydrolyzed using hydrochloric acid (7.5%) from 3 to 15 days to investigate the effect of long term acid hydrolysis on the evolution of the crystalline and double-helical structure changes, and its repercussion on the functionality. After 15 days, the degree of hydrolysis was 40.3 ± 0.8%. Micrographs revealed the granular structure loss after 6 days of hydrolysis. Acid hydrolysis decreased the crystallinity from 36.6 to 21.1% after 3 days but it increased to 27.0% after 15 days, while the degree of double helix and degree of order decreased after the acid treatment. Structural degradation of AS induced by the acid hydrolysis was reflected in the significant reduction of the enthalpy change of gelatinization and swelling, and the significant increase of the water solubility and water holding capacity, reaching maximum values at 9 (52.6 ± 1.0%) and 15 (266.4 ± 0.4%) days, respectively. Through the appropriate modification of the crystalline and double-helical structure by acid hydrolysis, the AS functionality can be regulated by adjusting the hydrolysis time, expanding the use of AS in the food industry.

Blending native starches is a feasible alternative for modifying the functional properties of starch dispersions. Granular interactions between starches lead to desirable properties that can be used for specific applications. Starch blends from amaranth (AmS) and achira (AS) were prepared at different proportions, and the pasting properties, flow curves and low-shear dynamic rheology were evaluated at 5, 7.5 and 10 g/100 g of solids. Granular interactions between starches were promoted when the solid content increased, affecting the formation of pasta. A polynomial model was used to predict the viscosity of the starch blends. The mechanical spectra showed that G′ and G″ had a slight dependence on the frequency. The incorporation of granules of AmS improved the stability of AS gels. Blending AmS and AS modified the rheological properties compared to pastes obtained from pure starches, mainly due to the concentration, size and granule interactions, resulting in low stability of the gels formed.

Sorghum, a competitive crop due to its agronomical advantages, has gained interest as functional food. Sorghum contains phytochemicals with health benefits and presents some antinutritional compounds such as condensed tannins (CTs). However, it is well known that CTs exhibit antioxidant capacity. This study evaluated the effect of Mexican nixtamalization on total phenols, CTs and antioxidant capacity using two varieties of sorghum. Different conditions of lime (0, 1 and 2%) and cooking time (20, 30 and 40 min) were tested to obtain the best treatment after optimization using multiple linear regression analysis, aiming to minimize the CTs content and maximize the antioxidant capacity. CTs were reduced at 27% in white sorghum and 90%, in red sorghum. Total phenols, flavonoids and antioxidant capacity had an inverse correlation with lime concentration and cooking time. The best conditions for preserving antioxidant capacity with low content of tannins were 1.13% of lime and 31.11 min cooking. The phenolic profile obtained by HPLC showed reductions in gallic and chlorogenic acids only in white sorghum, whereas catechin and quercetin decreased in both varieties. We concluded that nixtamalization effectively reduced CTs to safety intake values, allowing to preserve other phenolic compounds and antioxidant capacity.

Extrusion was used for obtaining corn masa. Particle size, Ca(OH)2 concentration, and tempering time had significant effects on the viscosity of extruded flours. Ground corn tempered for different periods of time (0.016–10 h) increased viscosity without application of heat. This behavior can be explained by the release of starches from the protein matrix. Viscoelastic properties of masas showed storage modulus (G′) > loss modulus (G″) for all samples. G′ and G″ increased as a function of tempering time, indicating higher water absorption capacity (WAC). The same behavior was found for Ca(OH)2 concentration, suggesting formation of cross-links between starch and polymers. Viscosity of masas modeled by the power law showed a value of n close to 0.1, suggesting that the dispersed solid phase was greater than the liquid phase. Index n and consistency coefficient K were associated with water absorption and viscosity, respectively. Regarding Ca(OH)2, the higher the Ca(OH)2 concentration, the lower the index n; ...

Two maize starches (Normal and Hylon VII) were hydrolyzed using HCL for 15 days at room temperature. The water holding capacity -WHC and oil holding capacity- OHC were evaluated to describe the changes during the reorganization of hydrolyzed material. The structure was assessed using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR). A hydrolysis degree of 20% was reached with a complete granular structure disruption. During acid hydrolysis, the rearrangement of decoupled double helices favored the order degree. The hydrolysis of the amorphous region decreased the enthalpy of gelatinization. This effect was more noticeable in the normal starch. The changes promoted during the hydrolysis favored the reorganization of the network resulting in high values in WHC and OHC for both starches. The acid-treated starches obtained could be used as fillers, employing these materials with induced crystalline regions.

Ohmic heating (OH) is an emerging technology with potential for pasteurization and enzyme inactivation in mango pulp. This research aimed to investigate the effect of OH and conventional boiling treatment (CT) at moderate pasteurization conditions (72 °C, 2 min) on the physicochemical characteristics and the polyphenol oxidase (PPO) residual activity in Ataulfo mango pulp. Pulp's physical features, such as titratable acidity (TA) and pH did not show differences (p > 0.05) between treatments, whereas OH increased the apparent viscosity of mango pulp (10.26–15.64%). This effect was associated to a higher release of insoluble fiber. Both thermal treatments affected the color (ΔE values > 5) of mango pulp. PPO inactivation reached 95.7 ± 5.9% after 15 s with both thermal treatments. In silico molecular dynamics suggested that temperature and pH contributed to the PPO inactivation by inducing modifications in its catalytic site and altering the protein-substrate interaction. Our results indicate that OH is an effective technology to inactivate PPO at moderate pasteurization conditions (72 °C, 15 s), with minimal modifications on the physicochemical properties of Ataulfo mango pulp.

Normal and high amylose corn starches were modified using HMDSO plasma at different time treatments. Changes in functional properties of starch granule, film-forming solutions (FFS) and films were investigated. SEM analysis revealed HMDSO coating deposition on the granule surface, which limited the amylopectin leach out from the granules to the continuous matrix, affecting the rheological properties of the FFS. The amylopectin restriction resulted in a low reinforcement of the network decreasing the viscosity as indicated by n and k values. Also, a gel-like behavior (G′ > G″) was observed when the amylose and time treatment increased, suggesting that the matrix becomes less elastic with softer entanglement. This behavior was confirmed by creep test and Burger model parameters. The plasma treatments allowed obtaining FFS with low viscosity, suitable for developing soft and hydrophobic films with low flexibility, as indicated by the decrease of the maximum stress, Hencky strain and permeance values.

In this study, the resistant starch (RS) formation, crystallinity, and double helical order of autoclaved (120 °C) normal (ANS) and high amylose (AHS) corn starches retrograded at ~4–26% of water content were investigated. ANS and AHS retrograded at ~25–26% of water content were more crystalline (~35–40%) and formed by more close-packed double helices (R1000/1022 cm−1 = 1.145–1.290). The highest content of RS (38.8%) was found in AHS retrograded at 25.52% of water content meanwhile in ANS, the maximum content of RS was 6.6% at 21.60% of water content despite its structural order was increased with the increase of water content. The recrystallization of amylopectin interfered with the formation of homogeneous crystalline structures of amylose preventing the formation of retrograded RS in ANS, while in AHS, a relationship between structure and RS formation was observed, suggesting that the close-packed double helices and the proportion of homogeneous amylose crystallites increased the resistance to enzymatic digestion.

Functional modifications of starch, such as paste properties, retrogradation, water absorption indexes, solubility, and swelling capacity, are induced by the amylose-lipid complex. This research comprehends the study of functional properties of extruded maize starch mixed with fatty acids (stearic acid, oleic acid, and maize oil) and the formation of amylose-lipid complexes. Maize starch with lipids (5 or 10 %), moisture (35 %) was extruded (single screw). Starch granule was modified by extrusion, to a lesser extent at 10 % of lipids, especially stearic acid, which covers starch granule surface. Viscosity decreased meaningfully with stearic acid addition. DSC showed both starch gelatinization enthalpy and amylose-lipid complex enthalpy for stearic or oleic acid, but it was just the first enthalpy for maize oil. X-ray diffraction showed orthorhombic crystals with or without the presence of lipids. Our results indicated that stearic acid yielded the highest amount of amylose-lipid complexes.

In this study, the effect of amylose content and cold plasma treatment on starch films properties was investigated. Films from normal (30%) and high amylose (50 and 70%) starches were subjected to hexamethyldisiloxane (HMDSO) cold plasma treatment. Morphological, structural, mechanical and barrier properties of the films were evaluated. The amount of remnant starch granules (RSG) in the films depended on the amylose content and on the gelatinization extent of the starch. This behavior was corroborated on the films from starch with 50% amylose, where the loss of RSG resulted in poor barrier properties and high hydrophilicity. Moreover, HMDSO cold plasma treatment incorporated methyl groups improving the hydrophobic properties and favored the helix ordering of the starch components resulting in a limited water-film interaction. Furthermore, the simultaneous effect of HMDSO coating and the ordering of the structures reinforced the surface of the films, improving the mechanical properties.

Acrylamide can be generated from food components during tortilla chips frying. Thus, the aim of this research was to study different nixtamalization processes as traditional (TNP) with lime [Ca(OH)(2)], ecological (ENP) with CaCO(3), classic nixtamalization (CNP) that uses wood ash and extrusion (EXT) with no Ca(+2) source on mitigating the acrylamide formation in deep-fat frying tortilla chips. Acrylamide quantification was done through HPLC–UV. Lower acrylamide content in tortilla chips was for CNP with 46.3 µg/kg, followed by TNP with 55.0 µg/kg, ENP with 694.6 µg/kg and EXP with 1443.4 µg/kg. Differences in acrylamide values among samples can be related to effect of cations (Ca(2+), Mg(2+), Fe(2+), Zn(2+), Na(+) and K(+)) present in wood ashes, lime and salts used as raw materials. Correlation of (r = 0.85; p

The kinetics of starch gelatinization is usually described as a first‐order reaction, that is, the rate of formation of gelatinized mass is assumed to be proportional to the unreacted amount. It is also assumed that the proportional constant, the reaction rate (k), has an Arrhenius‐type dependence on temperature. The equation derived from this model predicts that all the starch eventually gelatinizes at any given temperature for any k different from zero. However, it is well known that gelatinization only initiates above the so called “gelatinization temperature.” In this study it is employed an alternative model that properly describes the actual experimental behavior, which deviates considerably from the first‐order model prediction. The model introduces an empirical parameter that quantifies the extent of gelatinization when a starch‐water mixture is held at certain temperature for “long enough.” The gelatinization degree was evaluated by applying thermal treatments to 70% moisture‐content samples for 0, 0.5, 1, 3, 5, 7, and 10 min at several temperatures (61, 63, 65, 67, and 69°C). The gelatinization activation energy (EA) derived from the alternative model is 176 ± 10 kJ/mol. Since the proposed model closely reproduces the experimental behavior, it is suggested that this value better describes the actual process. The proposed model allows for the proper modeling of the starch‐gelatinization kinetics, which is relevant in starch gelatinization studies and in food processing industry.

The objective of the present work was to study the effect of annealing and concentration of Ca(OH)2 (lime) and calcium salts on the thermal and rheological properties of maize starch during an ecological nixtamalization process. Thermal and rheological properties of maize starch changed during the ecological nixtamalization process because of three main causes: the annealing phenomenon, type of calcium salt, and calcium salt concentration. In all treatments thermal properties (To, Tp, and Tf) of nixtamal starch increased owing to the annealing process, whereas the type of salt or lime increased thermal properties and decreased pasting properties in this order: CaCl2 > CaSO4 > Ca(OH)2 ≈ CaCO3. This behavior was because of the dissociation of each salt or lime in water. Anions (OH−) can penetrate much more easily into the starch granule and start the gelatinization process by rupturing hydrogen bonds. Additionally, amylose-lipid complexes were formed during the nixtamalization processes, as indicated by an ...

The objective of this work was to study the formation of resistant starch (RS) in tortillas from an ecological nixtamalization process compared with the traditional nixtamalization process. The RS increased through all the steps of tortilla production. It was found that the increase of the RS corresponds mainly to the formation of RS5 (V-amylose-lipid complex), but in tortillas two major types of RS coexist: RS5 and RS3 (retrograded starch). In general, tortillas from the ecological nixtamalization process gave higher values of protein, lipids, total dietary fiber, insoluble fiber, soluble fiber, and RS compared with tortillas from the traditional nixtamalization process and commercial flour. The highest glycemic index (GI) occurred in the tortillas from commercial flour, whereas tortillas from 0.4% CaCO3 and 0.6% CaSO4 were classified as medium-GI (GI 50–70). Tortillas from 0.6% CaCl2 had the lowest value of GI. The ecological nixtamalization processes caused significant differences in quality and nutrit...

The objective of this study was to assess thermal, rheological and quality properties of grain, masa (ground nixtamalized corn), and tortillas made with high-oil maize hybrids and compare them with landraces. Grains of high-oil hybrids were harder (flotation index 10–36) with high onset, peak and final gelatinization temperatures, which were reflected in lower masa and tortilla yield. However, the tortillas had higher oil content (3.2–4.5 g/100 g) than those made with landraces (2.9–3.0 g/100 g). Tortillas made with the yellow hybrids were softer (1.8 N). Pepitilla had the highest viscosity in grain, masa and tortillas, reflected in greater water absorption and masa and tortilla yield (1.61 kg/kg maize). A close relationship was found between G′ and G″ and retained pericarp and oil content in masa; higher content of natural gums produced firmer masa with higher viscoelasticity. The high oil content in tortillas reduced their water absorption and starch swelling capacity but inhibited starch retrogradation, so they remained softer during storage.

Functional confectionery can be exploited as a vehicle for the protection of phenolic compounds (PCs) and for enhancing absorption during the gastrointestinal (GI) process. In this study, a confection containing 20% of mango bagasse (MB), gelatin and pectin was formulated. The PC profile, antioxidant capacity, in vitro bioaccessibility and apparent permeability (Papp) during mouth-stomach-intestine digestion (15, 30, 60, 120 min) and in vitro colonic fermentation (6, 12, 24 h) were evaluated for MB and the mango bagasse confection (MBC). HPLC-DAD analysis showed that mangiferin (830.69 μg g-1) was the most abundant compound in MBC. Total PCs (4.14 mg g-1), quercetin (244.83 μg g-1), and gallic acid (GA) (285.43 μg g-1) were highly bioaccessible mainly at the intestine at 60-120 min of digestion. GA was the most bioaccessible compound. Total flavonoids (TFs) and condensed tannins (CTs) had the maximum bioaccessibility in the mouth and stomach, respectively. For the permeability studies, PCs showed efflux rather than uptake in the intestine. Those compounds that exhibited intestinal absorption were mangiferin > GA > total PCs > TFs, whereas quercetin and CT absorption was negligible. The antioxidant capacity remained unchanged along the GI, mangiferin and quercetin being the most likely compounds to exert this activity. Overall results indicate that MBC has higher bioaccessibility, absorption and antioxidant capacity than MB, suggesting an effective protective role of gelatin and pectin, giving insight into the potential of MBC as a functional food.

The tyrosinase is a binuclear copper enzyme that catalyzes the oxidation of phenolics compounds to quinones in presence of molecular oxygen, which subsequently polymerized to dark brown pigments. To evaluate the effect of ohmic heating (OH) on the inactivation kinetics of Agaricus bisporus tyrosinase the independent variables were: electric field strength (25, 30, 35 V/cm), process time (0–15 min) and temperature (50–58 ± 1 °C). The conventional thermal treatment (CT) was used as a control. The results showed that the electric field decreased the time (D-value) required obtaining the same degree of tyrosinase inactivation at a target temperature compared to the CT. This indicates that the electric field acted synergistically with temperature to inactivate tyrosinase. The activation energy (Ea) calculated for the CT was 227.32 kJ mol−1, while for the OH they were 146.52, 135.14 and 124.87 kJ mol−1 for electric field strengths of 25, 30, and 35 V/cm respectively. In this study, a direct relationship between the Ea and the electric field is shown. Results demonstrated that the OH is an effective technology to inactivate tyrosinase, allowing it to be used in thermal process such as pasteurization or blanching.

Extrusion is considered a high potential technology in the production of nixtamal corn flour (NCF); however, shear force and high temperature produce starch dextrinization, modifying the quality characteristics of NCF. This investigation evaluated the effect of feed moisture, temperature, calcium hydroxide and speed in a low-shear transport system (LSTS) on water absorption index (WAI), water solubility index (WSI), relative viscosity, pH and color of NCF. Feed moisture and temperature had a significant effect on most of the characteristics of the NCF, while speed of transport and calcium hydroxide did not. NCF obtained from the LSTS presented a higher WAI and a lower WSI, relative viscosity and luminosity than NCF produced by the traditional method; however, differences between them were not significant. Lack of difference in WSI between NCF produced by both methods indirectly show that LSTS produces a low dextrinization. Practical Applications The most common corn food products elaborated from nixtamal corn flour (NCF) are snacks, tortilla, porridge and tamal. The low-shear transport system (LSTS) may be used to produce NCF appropriate for any of these final products surpassing the extrusion-cooking process, which is mainly used to produce snacks. According to the results of this investigation, it is possible to use LSTS to obtain NCF with a lower degree of dextrinization, improving NCF quality.

We report the use of impedance spectroscopy to study the development of both, high compressive strength and low water absorption for different sand–bentonite mixtures + copolymer (styrene)-co-(methyl acrylate)-asphalt emulsion used for adobe production. Impedance spectra consisted of two semicircular arcs related to electrical properties and capillary porosity of the sand–bentonite mixtures. The compressive strength of the mixtures presented a strong correlation to their porosity. The results obtained show that a sand–bentonite mixture + copolymer (styrene)-co-(methyl acrylate)-asphalt emulsion can develop a combination of higher compressive strength with lower water absorption appropriate for production of high performance adobes.

Kinetic parameters of thermal inactivation of pectin methylesterase (PME) in a partially purified mango enzyme extract were determined. The PME of mango partially purified by salting out showed different patterns of thermal inactivation, indicating the presence of a thermostable fraction at 70 °C and a thermolabile fraction at lower temperatures. The inactivation of the thermostable fraction exhibited a linear behavior that yielded a z-value of 9.44 °C and an activation energy (Ea) of 245.6 kJ mol-1 K-1 using the Arrhenius model. The thermostable mango PME fraction represented 17% of total crude enzyme extract, which emphasizes the importance of residual enzyme activity after heat treatment.

Approximately 80% of sorghum phenolic compounds are linked to arabinoxylans by ester bonds, which are capable of resisting the digestion process in the upper gastrointestinal tract, compromising their bioaccessibility and biological potential. The aim of this study was to evaluate the effect of the extrusion process on the content of phenolic compounds in sorghum bran and its impact on phenolic compounds and antiradical and anti-inflammatory capacity. Results revealed that the extrusion process increased total phenol content in sorghum bran compared to nonextruded sorghum, particularly for extrusion at 180°C with 20% moisture content (2.0222±0.0157versus3.0729±0.0187 mg GAE/g +52%), which positively affected antiradical capacity measured by the DPPH and TEAC assays. The percentage of inhibition of nitric oxide (NO) production by RAW cells due to the presence of extruded sorghum bran extract was significantly higher than that of nonextruded sorghum bran extract (90.2±1.9%versus76.2±1.3%). The results suggest that extruded sorghum bran could be used as a functional ingredient and provide advantages to consumers by reducing diseases related to oxidative stress and inflammation.

Water molecules modify the properties of biodegradable films obtained from hydrophilic materials. Most studies dealing with thermal, mechanical and barrier properties of hydrophilic films are carried out under one relative humidity (RH) condition. The objective of this work was to evaluate the effect of the moisture content on the thermal, mechanical and barrier properties of chitosan films under several RH conditions. Microclimates, obtained with saturated salt solutions were used for conditioning samples and the properties of the films were evaluated under each RH condition. Chitosan films absorbed up to 40% of moisture at the higher RH studied. The percentage of elongation and the water vapour permeability increased while tensile strength, Young's modulus and glass transition temperature decreased, when the moisture content increased. The results suggest that the water molecules plasticized the polymer matrix, changing the properties when the films were in contact with high RH environments.

In this study, the structure of amorphous and crystalline of Ge:Sb:Te:O films, with oxygen content from 0 to about 28 at.%, have been analyzed using X-ray diffraction, impedance measurements and X-ray photoelectron spectroscopy. From these results, the location of the oxygen atoms in the crystallographic structure has been deduced. The results have shown that, in films with oxygen content below 10 at.%, Te, Sb and most of Ge are in metallic state and the free oxygen is probably located at the tetrahedral interstitial sites. In amorphous films with higher contents of oxygen up to 28 at.%, tellurium is forming part of the Ge:Sb:Te alloy, while some of the germanium and antimony form amorphous oxides. This amorphous oxides segregate to the grains boundaries during crystallization. Both, the free oxygen and germanium oxide formed, act as nucleation centers for crystallization. Due to the deficit of germanium and antimony thus created, the amorphous films crystallized as Sb2Te3 in the rhombohedral phase with segregation of the excess crystalline tellurium. Such diffusion-limited process increases the nucleation time in laser-induced crystallization.

The aim of this work is to study the mechanism of the amorphous-to-crystalline phase transformation in Ge 1 Sb 2 Te 4 films doped with oxygen using nanosecond laser pulses under isothermal annealing in the time scale of minutes. Experimental results show that the nucleation time, t nucl (minimum laser pulse duration for starting the laser-induced crystallization) depends on the oxygen concentration in the films. For those films with compositions in the range of 2-8 at.%, t nucl is shorter than that observed in films free of oxygen. In contrast, in films with oxygen in the range of 10-28 at.%, t nucl is longer than in the reference sample. Reflection and X-ray measurements on minute time scale have shown that in the films without oxygen annealed under isothermal conditions, the nucleation of the Ge 1 Sb 4 Te 7 metastable phase is first observed, which is subsequently transformed into the Ge 1 Sb 2 Te 4 crystalline phase. This effect increases the nucleation time in laser-crystallized materials. For films with 2-8 at.% of oxygen the first nucleation phase to be observed is the crystalline Ge 1 Sb 2 Te 4 , where it is assumed that the oxygen acts as the center of nucleation, therefore decreasing the nucleation time. In the films with oxygen concentration above 10 at.%, the thermal treatments leads to the formation of stable amorphous GeO 2 . This decreases the amount of available Ge and leads to the formation of crystalline Sb 2 Te 3 . The phase segregation in films with more than 10 at.% of oxygen, results in an increase in the nucleation and crystallization times in laser-induced crystallization. This crystallization behavior allows the possibility of having multilevel laser recording.

Thin amorphous films of GeSbTe have been widely employed in the technology used for phase change optical memory or compact disks. In this article, we report on measurements of resistance, transmittance, and X-ray diffraction in thin films with stoichiometric compositions of Ge 1 Sb 4 Te 7 , Ge 1 Sb 2 Te 4 , Ge 2 Sb 2 Te 5 , and Ge 4 Sb 1 Te 5. The resistivity, lattice constant, and the temperature at which transformation from the amorphous phase to the cubic crystalline structure occurs were calculated for each stoichiometric composition, and the energy activation was determined, applying Kissinger's model. It was found that the Ge 4 Sb 1 Te 5 composition has the highest crystallization temperature (425 K), the highest resistivity (0.178 Ω cm), the greatest E a (3.09 eV), and the lowest lattice constant ( a =5.975 A) in the cubic phase at 170 °C.

The purpose of this work is to investigate the isothermal phase transformation in thin films of Ge 2 Sb 2 Te 5 and Ge 1 Sb 2 Te 4 alloys. From experimental and computed simulations it was shown that if the kinetic behavior is interpreted employing the Johnson-Avrami-Mehl-Kolmogorov theory, three slopes can be observed: the first related to a metastable transformation, the second to the step between metastable and stable transformation, and the last to the stable phase nucleation and growth. From X-ray patterns it was found that a metastable phase, which appears during the beginning of crystallization for Ge 2 Sb 2 Te 5 and Ge 1 Sb 2 Te 4 thin films. corresponds to the Ge 1 Sb 4 Te 7 fcc composition.

The aim of this article is to study the mechanism of the amorphous-to-crystalline phase transformation in Ge1Sb2Te4 alloys doped by oxygen (in the range of 4–28 at. %) using the electrical, optical, and x-ray measurements. Experimental results have shown that samples with oxygen in the range of about 4–10 at. % first crystallize into the Ge1Sb2Te4 fcc phase at temperatures in the range 130–145 °C, at higher temperature (around 275 °C) the fcc phase is transformed into the Ge1Sb2Te4 hexagonal phase. In samples with oxygen in the range of 10–15 at. % the crystallization occurs in two stages producing samples where Ge1Sb2Te4 and the Sb2Te3 coexist. Samples with higher oxygen content, in the range of 15–28 at. % the films crystallized into the rhombohedral Sb2Te3 phase due to the formation of amorphous germanium oxide. The experimental results have been interpreted employing the Johnson–Avrami–Mehl–Kolmogorov theory. Using isothermal measurements and the time dependence of the Avrami exponent, three different crystallization mechanisms are proposed for material with different content of oxygen.

The comparison of the electrical parameters in amorphous chalcogenide, obtained using three different methods (electrical impedance, d.c. and the four-point resistivity measurements), has shown that impedance measurement is the most appropriate because it is able to separate the contributions of the bulk and contacts. For that reason, impedance measurements provide the real values for the electrical parameters of the material. In addition, the impedance measurements were able to detect the initial stages of the amorphous-to-crystalline phase transition.

When electrical conductivity (EC) is studied in food hydrocolloids, such as starch, molecular structure is important because conductivity depends on the interaction of water with charged carboxyl group or hydroxyl groups (Marcotte et al. 1998). Several authors have found that EC of starch-water composites increases with temperature and decreases during starch gelatinization (Wang and Sastry 1997; Karapantsios et al. 2000; Li et al. 2004). This behavior is explained considering granule swelling, increase of viscosity, and reduction of the area for starch particle movement. Decreasing water content in the material decreases EC (Lewicki Piotr 2004).

Approximately 50% of the original whole fruit mass, after citrus processing for juice, consist of the peel, membranes and seeds. Citrus residues consist mainly of insoluble fiber (celluloses) and a small proportion of soluble fiber (hemicelluloses and pectin). For this reason, citrus residues could be considered as a potential high fiber ingredient that is used for food industry. In this study, lemon residues were extruded to modify and increase their soluble fiber fraction. Surface response methodology with six central points and six axial points was used to evaluate the changes in dietary fiber fractions in lemon residues. The independent variables studied were extrusion temperature (from 59.77 to 110.63°C), moisture content of the sample (from 33.18 to 66.82%) and screw speed (from 3.18 to 36.82). The extrusion process increased the soluble fiber from 38.60% in unprocessed lemon residues to 40.00 to 50.01% in extruded samples. The highest content of soluble fiber was 50.00% when operating conditions were high in temperature (100°C), low in moisture content (40%) and low in screw speed (10 rpm). The results of this study indicate that extrusion is a process that has the capability to transform insoluble fiber to soluble fiber in lemon residues. Key words : Lemon residues, extrusion, dietary fiber.

In this letter we propose a simple computer stochastic model to represent and gain some insight into the kinetics of transformation in materials with metastable phase formation. This model explains deviations from the well-known Johnson–Mehl–Avrami–Kolmogorov kinetics theory and predicts the three slopes in Avrami’s plot. The model predictions were compared with experimental results obtained from thin-film samples of Ge2Sb2Te5 during isothermal phase transformations. The model includes the two-stage transformation and is capable to reproduce the experimental transformation curves.

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.

An optical set-up was developed to measure transmitted and scattered light in real time using a photodiode array as a detector and tested during starch heating. Statistical parameters calculated were Partial Integrated Scattering (PIS) and variance. Understanding behavior of starch under heat treatment in the presence of water is very important in food industry. The structure of heat ed starch granule changes depending on differ ent factors like pH, solvent type and amount, enzime presence, amylose/amylopectin rela tion, etc., such changes has been attempted by using several techniques. In this work, solutions in distilled water of amylopectin, were evaluated. Calcium hydroxide solution was also tested and mixed with previous amylopectin samples to evaluate any interaction in a two-phase system. A close relationship was found between the observed optical signals with literature reported structure changes in starch, demonstrating that the system developed has potential to be used in a real industrial process for monitoring and control. Keywords: Starch, light transmission, light scattering, starch gelatinization, real-time control

In this study, the objective was to evaluate optical properties of a corn starch-water mixture as descriptors of its behavior under processing conditions. A solution of corn starch in water was prepared and heated from 25 to 85°C in a temperature-controlled optical cell. For the measurement of optical properties, a polarized laser beam modulated through a photoelastic modulator and an analyzer, was used as optical probe. It was possible to measure transmitted light, along with optical rotation. Optical measurements showed changes related to temperature dependent phenomena such as starch granule swelling and gelatinization, in the ranges 25 to 60°C, 60 to 85°C. Above 80°C transmission values were higher, due to the solution clarification caused by corn starch gelatinization. Regarding optical rotation, it was difficult to obtain reliable measurements at low temperatures due to the high turbidity of the system. However, once gel was formed at higher temperatures, optical rotation and light transmission increased. This study demonstrated that optical techniques are suitable for the study of the behavior of water-starch mixtures under processing conditions such as heating, revealing a promising future for the monitoring of such phenomena in the production line to lower costs and improve product quality.

Solutions of bovine serum albumin protein were heated from 30 to 85°C in a temperature-controlled optical cell equipped with air-convective and ohmic heating systems. A polarized laser beam passed through a photo-elastic modulator was used to measure system changes in optical rotation. Results using both the air-convective and the ohmic heating systems showed that when the protein system was heated, an increase in absolute value of optical rotation occurred close to the temperature of denaturation of the protein. Both heating systems were compared, evaluating data points spread and variation in calculated temperature of denaturation for the replicates. Although no improvement in these parameters was obtained with ohmic heating when compared to those obtained with the air-convective system, the optical change related to protein denaturation was more clearly observed. Because ohmic heating strongly interacts with the sample under study, samples with low polarity and not susceptible to electrolysis should be used to avoid electrical effects; regardless, ohmic heating coupled to optical systems could also be a useful tool for the evaluation of interaction of electric field with biological systems optically active.