Mechanochemical degradation of potato starch paste under ultrasonic irradiation

In the paper, changes in the molecular weight, the intrinsic viscosity and the polydispersity (molecular mass distribution) of treated potato starch paste were studied under different ultrasonic conditions which include irradiation time, ultrasonic intensity, potato starch paste concentration, and distance from probe tip on the degradation of potato starch paste. Intrinsic viscosity of potato starch paste was determined following the ASTM (American Society for Testing and Materials) standard practice for dilute solution viscosity of polymers. Molecular mass and polydispersity of potato starch paste were measured on GPC (Gel Permeation Chromatography). The results showed that the average molecular mass and the intrinsic viscosity of starch strongly depended on irradiation time. Degradation increased with prolonged ultrasonic irradiation time, and the increase of ultrasonic intensity could accelerate the degradation, resulting in a faster degradation rate, a lower limiting value and a higher degradation extent. Starch samples were degraded faster in dilute solutions than in concentrated solutions. The molecular mass and the intrinsic viscosity of starch increased with the increase of distance from probe tip. Our results also showed that the polydispersity decreased with ultrasonic irradiation under all ultrasonic conditions. Ultrasonic degradation of potato starch paste occured based on the mechanism of molecular relaxation of starch paste. In the initial stage, ultrasonic degradation of potato starch paste was a random process, and the molecular mass distribution was broad. After that, ultrasonic degradation of potato starch paste changed to a nonrandom process, and the molecular mass distribution became narrower. Finally, molecular mass distribution tended toward a saturation value.

Electroneutral Quaternization/Sulfosuccination for Alleviating the Adverse Effect of Paste Aging on the Properties of Corn Starch Film

For the purpose of alleviating the adverse effect of paste aging on the properties of corn starch film, a series of electroneutrally quaternized/sulfosuccinylated starches（EQSS） with different degrees of substitution（DS） were synthesized via the quaternization/sulfosuccination of acid-thinned corn starch（ATS） by varying the amounts of N-（3-chloro-2-hydroxypropl） trimethylammonium chloride, maleic anhydride, and sodium hydrogen sulfite. The influence of paste aging on the properties of starch film cast from heat-induced starch paste was investigated and the properties were explored in terms of tensile strength, elongation, work at break, degree of crystallinity, and flex-fatigue resistance. The experimental results showed that the paste ageing generated adverse influence on the elongation, work at break, and flex-fatigue resistance of starch film. Further experiments showed that electroneutral quaternization/sulfosuccination of starch were able to alleviate the negative effect of paste ageing on the elongation, work at break, and flex-fatigue resistance, thereby obviously enhancing the elongation, work at break and flex-fatigue resistance, and thus reducing the drawback of brittleness. The enhancement depended on the amounts of the substituents introduced. With the increase in DS value, the elongation and work at break as well as flex-fatigue resistance continuously rose, whereas the tensile strength gradually reduced.

A plastidic ATP/ADP transporter gene, IbAATP, increases starch and amylose contents and alters starch structure in transgenic sweetpotato

A plastidic adenosine triphosphate（ATP）/adenosine diphosphate（ADP） transporter（AATP） is responsible for importing ATP from the cytosol into plastids. In dicotyledonous plants, increasing ATP supply is a potential way to facilitate anabolic synthesis in heterotrophic plastids. In this study, a gene encoding the AATP protein, named Ib AATP, was isolated from sweetpotato（Ipomoea batatas（L.） Lam.）. Transcripts of Ib AATP were predominantly detected in the storage roots and leaves and were induced by exogenous sucrose and subjected to circadian rhythm. Transient expression of Ib AATP in tobacco and onion epidermal cells revealed the plastidic localization of Ib AATP. The overexpression of Ib AATP in sweetpotato significantly increased the starch and amylose contents and led to enlarged starch granules. The IbA ATP-overexpressing plants showed altered fine structure of amylopectin, which contained an increased proportion of chains with a degree of polymerization（DP） of 10–23 and a reduced number of chains with a DP of 5–9 and 24–40. In addition, starch from the transgenic plants exhibited different pasting properties. The transcript levels of starch biosynthetic genes, including Ib AGP, Ib GBSSI, Ib SSIIV, and Ib SBE, were differentially regulated in the transgenic plants. These results revealed the explicit role of Ib AATP in the starch biosynthesis of sweetpotato and indicated that this gene has the potential to be used to improve starch content and quality in sweetpotato and other plants.

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.

The Relationship Between Chinese Raw Dumpling Quality and Flour Characteristics of Shandong Winter Wheat Cultivars

Dumpling is one of the most important traditional wheat products in China. Dumpling quality is determined by the characteristics of both flour and filling, thus improvement of flour quality plays an important role in improving dumpling quality. Thirty-nine Shandong winter wheat cultivars and advanced lines sown in Jinan, Shandong Province, China, in the 2008-2009 cropping season were used to determine genetic variation in Chinese raw dumpling quality and its relationship with flour characteristics. Large variations were observed for protein quality parameters in comparison with starch properties. Variation in color of the raw dumpling sheet was broader than that of sensory evaluation parameters of boiled dumpling among tested wheat cultivars, indicating the large influence of filling on dumpling color. Two cultivars, Jimai 20 and Zimai 12, were identified as possessing very good quality of raw dumpling, and 21 cultivars and advanced lines showed good quality. Protein and total starch content influenced the L＊ value of raw dumpling sheets. L＂ value at 0 and 2 h after sheeting were significantly influenced by protein content （r=-0.46 and -0.52, P〈0.01） and total starch content （r=0.55 and 0.57, P〈0.01）, respectively. Flour yellow pigment was significantly corrected with a＊ （r=-0.67 and -0.62, P〈0.01） and b＊ （r=0.87 and 0.84, P〈0.01） value of raw dumpling sheets at 0 and 2 h after sheeting, respectively. Gluten strength parameters such as farinograph mixing tolerance index （MTI, r=-0.55, P〈0.01） were positively associated with appearance. MTI and energy were also significantly and positively correlated with elasticity of raw dumpling, with r=-0.54 and 0.47 （P〈0.01）. The positive relationships between peak viscosity （r=0.51, P〈0.01）, breakdown （r=0.54, P〈0.01）, and smoothness of raw dumpling were also observed. Therefore, it is suggested that breeding programs should give more attention to gluten strength and starch pasting parameters for raw dumpling quality improvement.

Differential expressions among five Waxy alleles and their effects on the eating and cooking qualities in specialty rice cultivars

Eating and cooking qualities（ECQs） of rice are important attributes due to its major influence on consumer acceptability. To better understand the molecular mechanism of the variation in ECQs, we investigated and compared the expressions among different alleles of the Waxy（Wx） gene and its effect on ECQs in specialty rice cultivars. The results showed that the accumulation of amylose was positively and significantly correlated to the level of mature Wx m RNA and granule-bound starch synthase I（GBSS I） in developing rice grain at 12 days after flowering. The amount of GBSS I and its activity together are the main factors controlling amylose synthesis. Differences in ECQs among five Wx allele types were investigated in samples from 15 rice varieties. The apparent amylose content（AAC） and gel consistency（GC） were similar in each type of Wx allele. The AAC followed the order, Wx^a type〉Wx^in type〉Wx^b type〉Wx^mq type〉wx. Contrary to this, the GC showed an opposite trend compared to AAC. There was a wide variation in rapid visco analyzer（RVA） profile among five Wx allele types, while varieties sharing a specified Wx allele had basically the similar RVA profile, although there was a slight difference in some RVA parameters, peak, hot paste and cool paste viscosities.