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The objective of this work was to analyze the morphological and physicochemical properties of bean starch and its use in nanoencapsulation by spray drying. Starch purity was 81.21 ± 1.43% db with a resistant starch content higher than a commercial corn starch, but with a high protein content and a low amylose content. Starch granules presented smooth surfaces, polyhedral shape and sizes from ~ 1 to 6.3 µm. Black bean starch exhibited an A-type X-ray diffraction pattern with a crystallinity highest than corn starch. Black bean starch showed higher thermal stability than a commercial corn starch. At 90 °C, solubility was 31.0% and swelling power was 31.2 g g−1. The black bean starch gel showed a high stability under refrigeration and freeze–thaw. Small particles and viscosity profile suggested the potential application of black bean starch as wall material during nano spray drying. Black bean starch tends to form spherical aggregates during nano spray drying due to the protein content. Capsules size was in the range of 1.0–2.5 µm, however were observed agglomerated particles by SEM. The encapsulation efficiency of l-ascorbic acid was 36.88 ± 0.55%. The results indicate that black bean starch possesses properties with potential applications in food industries.

Gluten-free and high indigestible carbohydrate food development is a topic that deserves investigation because of an increased focus on gluten intolerance and celiac disease and on metabolic disorders caused by overweight and obesity. Here, chickpea and maize flours were used as sources of protein and carbohydrate (because of the level used in the mixture) and unripe plantain as an indigestible carbohydrate source in composite gluten-free spaghetti elaboration. The mixture of unripe plantain, chickpea, and maize was used at different levels to prepare spaghetti (samples S15Pla and S25Pla); control pasta was made of 100% semolina (S100Sem), and a 100% unripe plantain flour (S100Pla) pasta was also evaluated. In vitro amylolysis rate of fresh and stored (three and five days) spaghetti was assessed. The spaghetti with 100% unripe plantain (S100Pla) had higher resistant starch (RS) content than the control sample and the two cooked composite gluten-free spaghettis (S15Pla, S25Pla), and RS further increased wi...

Oscillatory mechanical tests are commonly used for characterizing the rheological properties of starch gels. Although widely used, simple phenomenological models (e.g., Maxwell and Kelvin-Voigt) do not suffice for describing the viscoelastic dynamics of starch gels in the face of shear stress applications. Given the complex nature of starch gels, it is expected that mechanical dynamics are expressed over a wide range of time scales. From a phenomenological standpoint, this work considers the relaxation spectrum as a tool for characterizing viscoelastic properties of starch gels. To this end, 15% w/w gels made of four native starches (wheat, potato, corn and banana) were prepared and dynamic oscillatory measurements were performed at various strain magnitudes. The relaxation spectrum was estimated by fitting experimental data by the application of Tikhonov regularization procedure. The number and relative intensity of the peaks obtained from the interpretation of the relaxation spectrum were suitable to distinguish some features of the viscoelastic properties of the starch gels. The presence of a dominant peak at about 0.1 s was observed for all gels, whose resolution is enhanced for high strain magnitudes. This indicates that strong flow patterns increase the homogenization degree of starch gels. Overall, the results showed that the relaxation spectra can be considered a signature of the viscoelastic properties of specific starch gels.

Filmogenic solutions based on chayotextle (Shechium edule Sw.) starch mixed with microcapsules of resistant starch (RS) containing ascorbic acid (AA) were used as coatings for guavas. The viscosity properties of the coatings were affected by the concentration of microcapsules in the filmogenic solution. Fruits were coated by dipping them in filmogenic solutions without microcapsules (control) or in solutions with a concentration of microcapsules of 6.25% or 12.5%. Fruits were stored under controlled conditions (4 °C, 65% relative humidity), and the loss of weight, changes in the respiration rate (RR) and physicochemical parameters were assessed. In general, fruits coated with the control solution and solutions containing 6.25% and 12.5% microcapsules showed significant changes in the content of total soluble solids (TSS), pH, and titratable acidity (TA). Significant decreases in RR, firmness and weight were observed in fruits covered with the 12.5%, 6.25% and control solutions, respectively. Fruits covered with edible coatings showed a decrease in ripening, with lower values for their physicochemical properties and reduced changes in surface color compared with uncoated fruits.

The evolution of acid hydrolysis (sulfuric acid 3.16M) at the onset gelatinization temperature (57.73 � 0.72°C) of native corn starch was monitored. A first-order kinetics fitting was used to estimate the mean hydrolysis time (tH ¼ 29:26 � 3:86min) and maximum conversion ðX 1 ¼ 96:62 � 2:70%Þ. Amylose content presented a sharp decrement of about 90% in the first 30min. XRD results indicated A-type to B-type crystallinity transition in the first 10min, with maximum crystallinity increase of about 14% after 30min. SEM micrographs showed that hydrolysis disrupted granule morphology from regular oval-like shape to irregular geometries with aggregation of small-size debris. Granule size distribution broadened as hydrolysis proceeded due to fragmentation-adhesion phenomena of eroded starch granules. Fast changes in the thermal effects during the first minutes were caused by molecular rearrangements due to fast hydrolysis of amylose in the amorphous regions. Steady shear rate and oscillatory tests showed a sharp viscoelasticity decrease caused by amylose degradation.

Banana starches (BS) were isolated from Enano, Morado, Valery and Macho cultivars. The BS possessed B-type crystallinity and an amylose content varying from 19.32 to 26.35%. Granules had an oval morphology with different major-to-minor axis ratios, exhibiting both mono- and bi-modal distributions and mean particle sizes varying from 32.5 to 45 μm. BS displayed zeta-potential values ranging between -32.25 and -17.32 mV, and formed gels of incipient to moderate stability. The enthalpy of gelatinization of BS affected the crystalline order stability within the granules. In-vitro digestibility tests showed fractions as high as 68% of resistant starch. Rheological oscillatory tests at 1 Hz showed that BS dispersions (7.0%, w/w) exhibited Type III behaviour, attributed to the formation of a continuous phase complex three-dimensional amylose gel reinforced by swollen starch granules acting as fillers. Amylose content and granules morphology were the main factors influencing the BS properties.

Commonly, the interpretation of starch XRD patterns is hampered by the lack of sharp intensity peaks and the presence of a broad background band. This work proposes a fractal analysis approach for the analysis of XRD patterns obtained from starches. The idea behind the fractal analysis approach is that the broad background pattern contains information pertaining the complexity of the material structure that presumably is arranged within fractal geometries. Thus, the quest is to detect regularities reflected as auto-correlations of the complex intensity signal. The fractal rescaled range (R/S) analysis is proposed in this work to obtain an index for the regularity of the complex intensity signal. In turn, such regularity index should reflect the regularity of the complex starch structure. The approach is illustrated with native starches from maize, banana, and potato, showing that the former is more regular (i.e. more ordered starch structure) than the latter two. Gelatinization is used to contrast the fractal analysis results. In turn, it is shown that gelatinized starches exhibit a nearly amorphous structure reflected as non-correlated XRD sequences.

Three starches from different botanical sources were stored at different temperatures during four days in order to monitor their retrogradation by means of fractal analysis. To this end, digital images were obtained by sample sectioning and scanning electron microscopy (SEM). Fractal dimension estimation and lacunarity analysis were performed over SEM micrographs, showing that (i) as already reported in the recent literature, fractal dimension is directly related to gelatinization temperature, and (ii) the storage temperature and the starch botanical source affect strongly the heterogeneity (quantified in terms of lacunarity) of retrograded starches. Overall, the results in this work yield important insight on retrogradation, providing guidelines for predicting growth models for retrogradation.

The development of functional foods with low glycemic index and high levels of RS are of importance in the fight against the rapidly increasing rates of obesity and chronic diseases in modern societies. In this work, three cereal bars containing white maize, blue maize, or unripe banana flours were prepared. The proximal composition, in vitro starch digestibility and product acceptability were evaluated. The bar prepared with blue maize exhibited the highest level of protein and fat, and that containing white maize the highest dietary fiber and indigestible fraction contents. However, the product prepared with unripe banana flour showed the highest total and rapidly digestible starch levels, while that added with blue maize exhibited greater slowly digestible starch values. No difference in RS content was detected among the three bars. The starch hydrolysis indices and predicted glycemic indices of the three preparations were low (40–54% and 42–54%, respectively). Similar acceptation scores were recorded for the three experimental bars. Cereal bars with variable starch digestibility features and good acceptation by consumers may be prepared following the proper choice of functional ingredients.

In this study, some morphological, physicochemical, and the initial characterization of the starch granule enzymes of blue and white maizes of small and large granules are described. Starch was isolated from blue and white maizes, and the small and large granules were separated. The efficiency of separation was higher in large granules than small of the blue maize starch. The amylose content was slightly greater (1.3%) in large granules than smaller in both starches studied. No differences in the average gelatinization temperature were found between large and small granules, but the enthalpy of gelatinization value was higher in the small granules. The electrophoretic pattern showed that the granule-bound starch synthase (GBSSI) had higher expression in large than small granules and that explain the higher amylose content in the former granules. The differences showed in the starch biosynthesis enzymes in small and large granules might explain partially the physicochemical and functional properti...

Chickpea flour (CF) was prepared and used as an ingredient for elaboration of bread with different levels of wheat versus CFs (80 : 20 and 60: 40). Available starch (AS), resistant starch (RS), dietary fibre (DF), the in vitro starch hydrolysis indices (HIs), using a chewing/dialysis digestion protocol and the acceptability of the experimental bread were compared with those of a control bread prepared with wheat flour and baked in the laboratory. HIs were used to predict glyceamic indices (pGI). The bread analysed did not show differences in moisture, lipids and ash content, but CF-bread had higher protein, RS and DF amount than control bread. HI-based pGI for the CF-bread were 46.92 and 34.67%, which were significantly lower than control bread (65.31%), suggesting a `slow carbohydrate' feature for the CF-based goods. The slow digestion characteristics of chickpea are largely retained in the experimental bread. Data support the perceived health beneficial properties of legumes and CF might be used as a potential ingredient for bakery products with slowly digestible carbohydrates.

Flour obtained from toasted ground maize grains is widely consumed by different ethnic groups of Northern Mexico and Southwest USA as an energy source. In this work the in vitro digestibility, crystallinity, rheological, thermal, particle size distribution and morphological characteristics of toasted ground white and blue maize flours were studied. X-ray diffraction studies showed that the crystallinity content was reduced, but that the hydrolysis rate and the in vitro digestibility of starch were greatly improved by the toasting process. The relative amount of rapidly digestible starch showed an important increase at the expense of resistant starch content reduction. The thermal properties of white maize starch increased slightly, but those of the blue maize starch decreased slightly after toasting. Aqueous dispersions formed with 10% (w/w) flour were heated at 90 °C for 5 min to induce starch gelling, in order to resemble thin porridges. The dispersed gels exhibited higher elastic modulus (G′) than loss modulus (G′′) in the linear viscoelastic region, with blue maize dispersions displaying higher moduli magnitudes. At higher shear strain amplitudes, G′ decreased but G′′ first increased and then decreased (overshoot phenomenon). The effects of toasting on the structure and functionality of maize starch are explained on the basis of limited gelatinization of the granules. The results in this work provide insights for understanding the extensive use of pinole by impoverished ethnic groups, and more recently by high performance ultra-runners and athletes, as an energy food.

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.

The use of pigmented maize varieties has increased due to their high anthocyanins content, but very few studies are reported about the starch properties of these grains. The aim of this work was to isolate the starch granules from pigmented blue maize and carry out the morphological, physicochemical, and biochemical characterization studies. The proximate composition of starch granules showed high protein contents, after purification, the blue maize starch presented lower protein amount than starch from white maize (control). Although the purity of starch granules was increased, the damaged starch (determined for the Maltase cross absence) was also increased. Scanning electron microscopy showed the presence of some pores and channels in the blue maize starch. The electrophoretic protein profiles showed differences in the bands that correspond to the enzymes involved in the starch biosynthesis; these differences could explain the variation in morphological characteristics of blue maize starches against starch from white maize.