Luis A. Bello-Pérez

Antifungal effects of chitosan with different molecular weights on in vitro development of Rhizopus stolonifer (Ehrenb.:Fr.) Vuill

Determination of the molecular weight of three types of chitosan was carried out by HPSEC-RI. The effect of low, medium and high molecular weight chitosan was evaluated on development of three isolates of Rhizopus stolonifer. Image analysis and electronic microscopy observations were done in spores of this fungus. Germination of R. stolonifer in potato dextrose broth with chitosan was also evaluated. Results pointed out that the low molecular weight chitosan was more effective for inhibition of mycelial growth while the high molecular weight chitosan affected spore shape, sporulation and germination. Studies of scanning and transmission electron microscopy revealed numerous and deeper ridge ornamentations of the chitosan-treated spore.

Amylopectin: Structural, gelatinisation and retrogradation studies

Abstract Amaranth, waxy corn, and commercial corn amylopectins were enzymically debranched and their fractions separated by gel filtration. In all cases a bimodal distribution of chain lengths was found, containing a high proportion of short chains. Amaranth, waxy corn starches and commercial corn amylopectin displayed an A-type X-ray diffraction pattern, which is characteristic of cereal starches, whereas amaranth amylopectin did not show a well-defined pattern, suggesting that the former samples have granular structure. Gelatinisation and retrogradation data, by differential scanning calorimetry, showed a good agreement between starches and amylopectins of the same source. Amaranth starch and its amylopectin presented a lower tendency to undergo these changes compared to the remaining tested materials. The temperature effiect on retrogradation was more drastic for amaranth and waxy corn amylopectins.

Some structural, physicochemical and functional studies of banana starches isolated from two varieties growing in Guerrero, México.

Two varieties of green fruit banana growing in Guerrero State Mexico, were used for starch isolation. Starch yields from the bananas varieties “macho” and “criollo” were 43.8% and 11.8%, respectively. Thermal transition temperatures assessed by differential scanning calorimetry (DSC) were higher for “criollo” than for “macho” starch but the enthalpy changes in both starches were not different. Both starches showed A-type diffraction pattern, until now not reported for banana starches. Light microscopy revealed some structural characteristics of banana starches as shape and size and eccentric birefringence was observed under polarized light. The iodine-stained differed in their blue color intensity. The viscosity profiles of both samples evaluated with the Rapid Visco Analyzer (RVA) were similar, and the gelatinization temperatures agree with those obtained by DSC. The pastes formed from banana starches in general were opaque and the storage temperature had a slight effect on clarity.

Effect of Storage Time on In Vitro Digestibility and Resistant Starch Content of Nixtamal, Masa, and Tortilla

ABSTRACT 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...

Acid hydrolysis of native corn starch: Morphology, crystallinity, rheological and thermal properties

The acid hydrolysis of native corn starch at 35 °C was monitored during 15 days. After this time, the residual solids were about 37.0 ± 3.0%. First-order kinetics described the hydrolysis data, giving a constant rate of kH = 0.18 ± 0.012 days(-1). Amylose content presented a sharp decrement of about 85% and X-ray diffraction results indicated a gradual increase in crystallinity during the first 3 days. SEM micrographs showed that hydrolysis disrupted granule morphology from an initial regular shape to increasingly irregular shapes. Fractal analysis of SEM images revealed an increase in surface roughness. Fast changes in the thermal effects were caused by molecular rearrangements after fast hydrolysis of amylose in the amorphous regions in the first day. Steady shear rate and oscillatory tests showed a sharp decrease of the apparent viscosity and an increase of the damping factor (tan(δ)) caused by amylose degradation.

Protection of L. rhamnosus by spray-drying using two prebiotics colloids to enhance the viability

Protection of probiotics by substances considered as prebiotics can be an alternative to increase their viability in the large intestine. The objective of this study was to use two wall materials (native rice starch and inulin) without bonding agent to protect Lactobacillus rhamnosus during spray-drying and determine the viability of the microorganism under two storage conditions. For spray-drying conditions tested in this work the product yield with native rice starch (NRS) ranged between 65% and 74% whereas for inulin (IN) it ranged between 43% and 54%. In general, IN solutions exhibited higher outlet temperature than NRS dispersions. Capsules of IN had smaller particle size than those of NRS. Due to the higher hydrophilic nature of IN capsules as compared to NRS, IN capsules exhibited higher water activity than NRS capsules. Confocal microscopy showed marked differences between both wall materials, which could in turn cause differences in the release profile of encapsulated microorganisms. Agglomerates of NRS provided better protection to the microorganisms as evidenced by the lower reduction in viability when compared to IN, and this effect was corroborated by the stability study. It is possible to protect probiotics using both colloids, but differences in the viability and stability during storage were determined. The use of IN could prove beneficial in the encapsulation of probiotic strains since this carbohydrate is not hydrolyzed by human digestive enzymes and may act as prebiotic.

Physicochemical and Digestibility Properties of Double-Modified Banana (Musa paradisiaca L.) Starches

Banana starch was chemically modified using single (esterification or cross-linking) and dual modification (esterification-cross-linking and cross-linking-esterification), with the objective to increase the slowly digestible starch (SDS) and resistant starch (RS) concentrations. Physicochemical properties and in vitro digestibility were analyzed. The degree of substitution of the esterified samples ranged from 0.006 to 0.020. The X-ray diffraction pattern of the modified samples did not show change; however, an increase in crystallinity level was determined (from 23.79 to 32.76%). The ungelatinized samples had low rapidly digestible starch (RDS) (4.23-9.19%), whereas the modified starches showed an increase in SDS (from 10.79 to 16.79%) and had high RS content (74.07-85.07%). In the cooked samples, the esterified starch increased the SDS content (21.32%), followed by cross-linked starch (15.13%). Dual modified starch (cross-linked-esterified) had the lowest SDS content, but the highest RS amount. The esterified and cross-linked-esterified samples had higher peak viscosity than cross-linked and esterified-cross-linked. This characteristic is due to the fact that in dual modification, the groups introduced in the first modification are replaced by the functional group of the second modification. Temperature and enthalpy of gelatinization decreased in modified starches (from 75.37 to 74.02 °C and from 10.42 to 8.68 J/g, respectively), compared with their unmodified starch (76.15 °C and 11.05 J/g). Cross-linked-esterified starch showed the lowest enthalpy of gelatinization (8.68 J/g). Retrogradation temperature decreased in modified starches compared with unmodified (59.04-57.47 °C), but no significant differences were found among the modified samples.

Development and Characterization of Spaghetti with High Resistant Starch Content Supplemented with Banana Starch

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.

Amylopectin : properties and fine structure

Abstract Five amylopectins from different sources were studied to compare their physico-chemical properties and structure. Physicochemical properties such as iodine binding capacity (IBC), maximum absorption ( λ max ) and intrinsic viscosity ([η]) were assayed. Normal corn amylopectin and potato amylopectin gave high values of IBC whereas waxy corn, corn commercial and amaranth exhibited low values of this parameter; all values for λ max were in the range 525–595 nm and those for [η]varied from 23 to 104 ml/g. Results suggested structural differences in the amylopectins. These macromolecules were eluted by high-performance size exclusion chromatography (HPSEC) with refractive index (RI) showing different elution times, which indicate structural differences among such components. The five amylopectins were debranched with isoamylase and pullulanase, and the fractions, studied both by HPSEC with RI and by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD), showed structural differences among amylopectins and differences in debranched patterns of isoamylase and pullulanase.

Fiber Concentrate from Orange (Citrus sinensis L.) Bagase: Characterization and Application as Bakery Product Ingredient

Orange is a tropical fruit used in the juice industry, yielding important quantities of by products. The objective of this work was to obtain a dietary fiber-rich orange bagasse product (DFROBP), evaluate its chemical composition and its use in the preparation of a bakery product (muffin). Muffins containing two different levels of DFROBP were studied regarding chemical composition, in vitro starch digestibility, predicted glyceamic index and acceptability in a sensory test. DFROBP showed low fat and high dietary fiber contents. The soluble and insoluble dietary fiber fractions were balanced, which is of importance for the health beneficial effects of fiber sources. DFROBP-containing muffins showed the same rapidly digestible starch content as the reference muffin, whilst the slowly digestible starch level increased with the addition of DFROBP. However, the resistant starch content decreased when DFROBP increased in the muffin. The addition of DFROBP to muffin decreased the predicted glyceamic index, but no difference was found between the muffins prepared with the two DFROBP levels. The sensory score did not show difference between control muffin and that added with 10% of DFROBP. The addition of DFROBP to bakery products can be an alternative for people requiring low glyceamic response.