Relationship Between Degree of Starch Gelatinization and Quality Attributes of Parboiled Rice During Steaming

Paddy rice samples were parboiled by soaking at 65℃ for 180 min and steaming at 96℃ for 2–10 min,and then dried to achieve the final moisture content of 11% ± 1%. The degree of starch gelatinization （DSG） andseveral quality attributes （head rice yield （HRY）, color value and hardness） of parboiled rice were measured.Results showed that DSG （46.8%–77.9%）, color value （18.08–19.04） and hardness （118.6–219.2 N） allincreased following steaming. In contrast, the HRY increased （64.8%–67.1%） for steaming times between 2–4min but decreased （67.1%–65.0%） for steaming times between 4–10 min. Linear relations between DSG andcolor value （R2 = 0.87）, and DSG and hardness （R2 = 0.88） were observed. The suitable DSG of parboiled riceleading to the highest HRY was found to be 62.5%, obtained following 4 min of steaming.

Variation in Gelatinization Characteristics of Storage Root Starch During Sweetpotato Growth and Development

The differential scanning calorimetry (DSC) and rapid visco-analyzer (RVA) were used to determine the starch gelatinizationcharacteristics during the growth of three sweetpotato cultivars. The results showed that the starch contents of threesweetpotato cultivars all decreased as growth progressed. Changes of the amylose contents differing in harvesting datesshould be discriminated according to the cultivars. At the early harvests amylose contents of Xushu18 and Zheda9201were relatively high, but those of Zhe3449 were low. As the growth duration of sweetpotatoes prolonged, the peaks ofDSC thermograms tended to occur at a low temperature and not to be so obstrusive with the increased width of the peak.Obvious decreases were observed, values of onset, peak and conclusion temperatures, as well as enthalpy of phasetransitions, as growth time lengthened. The peak viscosities, as determined through RVA, showed a rising tendency asgrowth progressed. In addition, statistical analysis revealed that there were correlations between the amylose content andgelatinization characteristics to some extent, which were affected by genotypes evidently.

Viscosity reduction of tapioca starch by incorporating with molasses hydrocolloids

As a low cost non-staple food resource,the high-viscosity paste and poor gel-forming ability of tapioca starch limit its industrial application.Herein,molasses hydrocolloids that is a by-product of the sugar refining process was applied as a blending modifier to reduce the viscosity of tapioca starch paste.The test results of paste and rheological properties show that molasses hydrocolloids exhibited a good physical viscosity-reducing effect on tapioca starch paste.The irregular network structure and high K^(+)/Ca^(2+)ion contents of molasses hydrocolloids exerted wrapping,adhesion,barrier,and hydration effects on starch,leading to the reduction of viscosity.The scanning electron microscope images and textural analysis demonstrated that this strategy also improve the structure of tapioca starch gel and enhanced its puncture strength by 75.46%.This work shows the great potential of molasses hydrocolloids as a lowcost and desirable material for the viscosity reduction of tapioca starch.

Characterization of A-and B-type starch granules in Chinese wheat cultivars

Starch is the major component of wheat flour and serves as a multifunctional ingredient in food industry. The objective of the present study was to investigate starch granule size distribution of Chinese wheat cultivars, and to compare structure and functionality of starches in four leading cultivars Zhongmai 175, CA12092, Lunxuan 987, and Zhongyou 206. A wide variation in volume percentages of A- and B-type starch granules among genotypes was observed. Volume percentages of A- and B-type granules had ranges of 68.4–88.9% and 9.7–27.9% in the first cropping seasons, 74.1–90.1% and 7.2–25.3% in the second. Wheat cultivars with higher volume percentages of A- and B-type granules could serve as parents in breeding program for selecting high and low amylose wheat cultivars, respectively. In comparison with the B-type starch granules, the A-type granules starch showed difference in three aspects：（1） higher amount of ordered short-range structure and a lower relative crystallinity,（2） higher gelatinization onset（To） temperatures and enthalpies（ΔH）, and lower gelatinization conclusion temperatures（Tc）,（3） greater peak, though, and final viscosity, and lower breakdown viscosity and pasting temperature. It provides important information for breeders to develop potentially useful cultivars with particular functional properties of their starches suited to specific applications.

Use of two-stage dough mixing process in improving water distribution of dough and qualities of bread made from wheat–potato flour

The two-stage dough mixing process was innovated to improve the qualities of bread made from potato flour(PF) and wheat flour at a ratio of 1:1(w/w). The final dough was first prepared from wheat flour before being added with PF. The effects of the method on enhancing the dough qualities were verified, and the distribution of water in gluten-gelatinized starch matrix of the doughs was investigated. We observed that the bread qualities were improved, as reflected by the increase of specific volume from 2.26 to 2.96 m L g^–1 and the decrease of crumb hardness from 417.93 to 255.57 g. The results from rheofermentometric measurements showed that the dough mixed using the developed mixing method had higher maximum dough height value, time of dough porosity appearance, and gas retention coefficient, as well as enhanced gluten matrix formation compared to that mixed by the traditional mixing method. The results from low-field nuclear magnetic resonance confirmed that the competitive water absorption between gluten and gelatinized starch could restrict the formation of gluten network in the dough mixed using the traditional mixing process. Using the novel mixing method, gluten could be sufficiently hydrated in stage 1, which could then weaken the competitive water absorption caused by gelatinized starch in stage 2;this could also be indicated by the greater mobility of proton in PF and better development of gluten network during mixing.

Comparison of microwave and conventional heating on physicochemical properties and phenolic profiles of purple sweetpotato and wheat flours

The hydrothermal treatment assisted with microwaves on physicochemical properties and phenolic profiles of purple sweetpotato flour and wheat flour was studied and compared with those of conventional heat treatment.Both treatments significantly decreased the enthalpy change,pasting viscosity and gelling capacity of flours,while increasing particle size,gelatinization temperatures and content of resistant starch.Microwaves induced more severe damages on the starch granule morphology and crystallinity than conventional heat treatment,which could be attributed to the intensive friction and collision produced by electromagnetic waves.The total concentrations of hydroxycinnamic acid derivatives and anthocyanins in purple sweetpotato flour extracted using microwaves at 100℃ were 36%and 68%higher than those in the samples after conventional heat treatment at 100℃,respectively.Electromagnetic waves caused a higher extent of cell damage due to sudden temperature rise during microwave treatment.Overall,microwave treatment has potential to produce novel functionalities and nutritional values of flours and can be applied as an effective approach for other starch-based food products.