Effect of pH on the physicochemical and binder properties of tigernut starch

Effects of purple potato anthocyanins on the in vitro digestive properties of starches of different crystalline types

This study explored the potential of purple potato anthocyanins (PPAs) in regulating the digestive properties of starches of various crystalline types. In vitro digestion experiments indicated that PPAs inhibit the hydrolysis of rice starch (A-type) better than that of garden pea starch (C-type) and potato starch (B-type). Further structural assessment of different PPA-starch systems showed that PPAs and starch likely interact through non-covalent bonds, resulting in structural changes. Microstructural changes observed in the starches were consistent with the in vitro digestion results, and the chain length and proportions of short/long chains in amylopectin molecules affected the binding strengths and interaction modes between PPAs and starch. Hence, the three starches differed in their PPA loading efficiency and digestibility. These discoveries contribute to a deeper understanding of the mechanisms underlying the inhibition of starch digestibility by PPAs. They can aid the formulation of value-added products and low-glycemic-index foods.

The effects of pH and iron ions on the mechanical properties of pea starch hydrogels

In this study, the network strength of starch hydrogels was improved by adjusting the pH value (3-11.5) and adding iron ions (Fe3+), and the mechanical properties and swelling properties of the hydrogels were improved. The complex modulus of the starch hydrogel with a pH value of 11.5 and containing Fe3+ was above 3400 Pa. SEM showed that the hydrogel structure became more compact with the increase of pH value. In addition, the hardness of the hydrogel increased from 50.29 g at pH 3.0 to 215.1 g at pH 11.5, while the addition of 0.5 mol/L Fe3+ at pH 11.5 promoted a further hardness increase to 301.8 g. Moreover, the swelling rate of the hydrogel decreased from 670.2 % at pH 7.0 to 464.4 % at pH 11.5, and the addition of 0.5 mol/L Fe3+ further decreased the swelling rate to 191.8 %. Overall, the results indicate that the mechanical properties of starch hydrogels can be improved by making simple adjustments to the pH and the iron ion concentrations.

Gallic acid-fortified buckwheat Wantuo: characteristics of in vitro starch digestibility, antioxidant and eating quality

Gallic acid (GA), presented in various plant sources, is increasingly used as a nutritional food ingredient due to its prominent bioactive. In this work, common buckwheat Wantuo (BWT, a Chinese traditional starch gel food) was fortified with 1,3,5% (w/w) GA and assessed for physicochemical properties of flour as well as in vitro starch digestibility, antioxidant and eating quality of BWT. The results clearly showed that the hydration, pasting properties as well as gel microstructure and texture of gel were influenced with addition of GA, while the color of flours showed no significantly change. Hydrogen bonds interaction between GA and starch, more hydrophilic groups exposure and more acid hydrolysis of the starch were thought to be main reasons. Furthermore, combined with structural analysis of starch, the significantly decreased rapidly digested starch (8.62%)/slowly digested starch (12.90%) and increased resistant starch (78.48%) in BWT with 5% addition amount can be mainly due to digestive enzymes inhibition, formation of V-type conformation and alteration in the local structure of starch-phenol-enzyme complex. Meanwhile, the antioxidant activity of BWT-GA improved, where as its texture properties softened due to suppressed starch retrogradation. This study demonstrated the potential use of polyphenol as food ingredient to improve the nutritional properties and eating qualities of starch gel food.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05614-x.

Tiger Nut (Cyperus esculentus L.): Nutrition, Processing, Function and Applications

The tiger nut is the tuber of Cyperus esculentus L., which is a high-quality wholesome crop that contains lipids, protein, starch, fiber, vitamins, minerals and bioactive factors. This article systematically reviewed the nutritional composition of tiger nuts; the processing methods for extracting oil, starch and other edible components; the physiochemical and functional characteristics; as well as their applications in food industry. Different extraction methods can affect functional and nutritional properties to a certain extent. At present, mechanical compression, alkaline methods and alkali extraction-acid precipitation are the most suitable methods for the production of its oil, starch and protein in the food industry, respectively. Based on traditional extraction methods, combination of innovative techniques aimed at yield and physiochemical characteristics is essential for the comprehensive utilization of nutrients. In addition, tiger nut has the radical scavenging ability, in vitro inhibition of lipid peroxidation, anti-inflammatory and anti-apoptotic effects and displays medical properties. It has been made to milk, snacks, beverages and gluten-free bread. Despite their ancient use for food and feed and the many years of intense research, tiger nuts and their components still deserve further exploitation on the functional properties, modifications and intensive processing to make them suitable for industrial production.

Physicochemical properties and in vitro digestibility of proso millet starch after addition of Proanthocyanidins

The solubility and swelling power, pasting, structure, and digestibility properties of proso millet starch (PMS) with different concentration of proanthocyanidins (PA) were investigated. The results showed that with PA content increasing, the solubility and swelling power of starch increased, the PA accelerated the water absorption and expansion of starch. The results of pasting properties showed that PA increased the peak viscosity of starch, but decreased the setback and pasting temperature. A significant decrease in enthalpy value was measured by differential scanning calorimetry, the enthalpy value decreased from 14.98 J/g to 10.24 J/g at 20% PA concentration. The relative crystallinity of starch, as well as the ratio at 1049/1022 cm^-1, decreased due to the increasing PA concentration, indicating the ordered degree of starch reduced, while the hydrogen bonding in the system was enhanced by PA. The addition of PA decreased the RDS content of uncooked and cooked starch, the RS content increased. When the PA concentration was 20%, the RS content was 1.05 and 1.92 times for native starch, respectively, which significantly reduced the starch digestibility.

Physicochemical properties of starch obtained from Curcuma karnatakensis - A new botanical source for high amylose content

Curcuma karnatakensis, a member of Zingiberaceae, is endemic to the state of Karnataka, India. The structure and physicochemical properties of starch isolated from rhizomatous rootstocks of two samples - A and B were analyzed for the first time. Sample A contains 76.4 ± 0.3% of starch, of which 86.6 ± 0.4% is amylose, while sample B has 75.0 ± 0.4% of starch containing 84.6 ± 0.4% of amylose according to UV-Vis spectrophotometric analysis. The shape of the starch granules in both the samples is polygonal and cuboidal with a smooth surface, as revealed by SEM studies. The X-ray diffractogram indicated A type of polymorphs in contrast to other Curcuma species, where B types are reported. Since its high amylose content leads to an increased tendency to retrogradation and the formation of resistant starch, this taxon could become one of the major dietary sources of starch in the future. In addition, a source rich in amylose specifies its prospective application in the pharmaceutical and biodegradable film industry.

Physicochemical, Microstructural, and Rheological Characterization of Tigernut (Cyperus esculentus) Starch

The aim of this study was to characterize the physicochemical properties of starch isolated from two varieties of tigernuts. The results showed wide variations between the two types of tigernuts. Mean granule sizes were 11.1 and 6.1 μm, respectively, for starch from the yellow and black while amylose content ranged from 19 to 21%. Starch gels from the yellow variety were more stable to freeze-thaw and recorded 37.1% syneresis, compared to 56.5% after the first storage cycle. Pasting properties were significantly different (p < 0.05) among starch from the two tigernut varieties, with black recording higher peak viscosity, lower breakdown, and higher setback viscosity. Gels made from the yellow variety were clearer, softer, more adhesive, and more cohesive. Both gels showed a pseudoplastic flow behavior without thixotropy.

Physicochemical and morphological properties of resistant starch type 4 prepared under ultrasound and conventional conditions and their in-vitro and in-vivo digestibilities

In the present work, cross-linked resistant starch (RS4) was prepared under sonication and conventional conditions at various levels of pH (9-12) and cross-linker concentration (sodium trimetaphosphate/sodium tripolyphosphate 99:1, 5-15%). It was found that phosphorous and resistant starch content was generally increased by increasing the cross-linker concentration, pH and application of sonication. The damage to the surface of sonicated granules was revealed by scanning electron micrographs. The presence of cross-linked phosphorous groups was demonstrated by FT-IR results through the appearance of a new peak at wave numbers of 1248-1252 cm^-1 that was more conspicuous in sonicated cross-linked samples. Sonicated cross-linked starches showed higher gelatinization temperatures and lower degrees of crystallinity, while no changes was detected in terms of A-type crystalline pattern. The development of viscosity was diminished prominently by the extreme cross-linking reactions in both sonicated and conventional cross-linked starches. The least glycemic index value was obtained for sonicated cross-linked starches which was negatively correlated to their higher RS content measured in-vitro. These results provide novel information on the preparation of cross-linked resistant starch under sonication conditions.