Effect of wheat puroindoline alleles on functional properties of starch

Puroindoline a and b (Pina, Pinb) form the molecular basis of bread wheat grain hardness. Varieties with a softer endosperm and a wild genotype, in which both Pina and Pinb were present, seemed to produce less damaged starch flour than hard varieties, where Pin mutations occurred and changed the starch rheological properties. The functional property of starch samples extracted from wheat varieties with different Pin alleles was evaluated. Starch morphology was characterized by scanning electron microscopy and laser light scattering. Thermal properties were evaluated by differential scanning calorimetry. Amylose content, starch damage and rapid visco-analyser (RVA) parameters were also determined. Significant variations (P < 0.05) were identified between different Pin variants for the distribution pattern of starch granule volume, amylose content, starch damage, RVA viscosity breakdown and retrogradation, gelatinisation transition temperatures and enthalpies. Hard genotypes presented higher medium diameter granules and lower enthalpic values. However, the differences detected are more evident among varieties that present both Pina and Pinb, than among those presenting only one of the two (a or b).     

Effect of aqueous ozonation on the pasting,flow and gelatinization properties of wheat starch

Wheat starch–water suspensions were exposed to ozone gas for 15, 30, and 60 min at 5 °C at a concentration of 0.00042 g dissolved ozone/100 g. Pasting properties were determined by using a Rapid Visco Analyzer (RVA) while a Bohlin rheometer was used to obtain flow behaviour (n) and consistency (K) indices. An enzymatic method using glucoamylase was applied to calculate percent starch gelatinization. Pasting temperature (P_T) of ozonated starch samples decreased significantly (P < 0.05) as compared to that of native starch. Cooking stability starch samples increased upon ozonation indicated by lower breakdown viscosity (B_V) values. The retrogradation tendency of wheat starch samples was reduced after ozonation which was indicated by lower setback viscosities (S_V). Native and ozonated starch samples exhibited a shear-thinning behaviour with values of flow behaviour indices (n) between 0.57 and 0.76. The greater n values obtained for ozonated starch samples as compared to native starch showed that ozonation increased the shear-thinning behaviour of wheat starch. Percent gelatinization for all ozonated starch samples were significantly higher than the control starch samples (P < 0.05), probably due to, weakened hydrogen bonding between the starch molecules and partial depolymerization of starch molecules by ozonation.     

热加工对小麦蛋白结构和消化特性的影响

研究100℃热处理不同时间（5min、15min、30min）对小麦蛋白分子结构及其体外消化的影响。结果表明,随着热处理时间的增加,麦谷蛋白和麦醇溶蛋白的α-螺旋结构逐渐减少,无规则卷曲结构的相对含量分别增加了8.2%、7.98%,这与小麦蛋白的电镜微观结果一致;麦谷蛋白与麦醇溶蛋白的平均粒径在热处理30min时分别达到了237.4μm、254.3μm;根据凝胶电泳结果显示,热处理对麦醇溶蛋白和麦谷蛋白的亚基分子量没有显著影响;在特定的热处理时间内,小麦蛋白的消化程度与加热时间呈正比关系。综上,麦醇溶蛋白与麦谷蛋白在热处理下发生的结构变化具有一致性,且在100℃ 30min处理下的小麦蛋白具有最高的消化率。     

Effect of phytochemical extracts on the pasting,thermal, and gelling properties of wheat starch

Pasting, thermal and gel textural properties of wheat starch were studied in the presence of phytochemical extracts from pomegranate peel (C18), green tea (C53), Chinese hawthorn (C54), and Chinese gall (C46). All the four extracts increased the breakdown values and reduced the final viscosity. C18, C46, and C53 increased the peak viscosity. C18 and C46 reduced peak time and hot paste viscosity. All the four extracts reduced gel hardness. C46 increased gel adhesiveness. C46 facilitated the gelatinization of starch with earlier onset of T_o, T_p and T_c and a higher melting enthalpy whereas C18 and C54 prolonged the T_o, T_p and T_c and decreased the melting enthalpy. All phytochemical extracts caused earlier onset of T_o and T_p of amylose inclusion complex melting without altering the enthalpy. Scanning electron microscopy revealed that phytochemical extracts could cause looser gel matrices of dried wheat starch gels. Colour observation showed phytochemical extracts imparted different colours to wheat starch gels.     

Effect of gaseous ozone treatments on DON,microbial contaminants and technological parameters of wheat and semolina

Deoxynivalenol (DON) is an important mycotoxin produced by several species of Fusarium. It occurs often in wheat grain and is frequently associated with significant levels of its modified form DON-3-glucoside (DON-3-Glc). Ozone (O₃) is a powerful disinfectant and oxidant, classified as GRAS (Generally Recognised As Safe), that reacts easily with specific compounds including the mycotoxins aflatoxins, ochratoxin A, trichothecenes and zearalenone. It degrades DON in aqueous solution and can be effective for decontamination of grain. This study reports the efficacy of gaseous ozone treatments in reducing DON, DON-3-Glc, bacteria, fungi and yeasts in naturally contaminated durum wheat. A prototype was used to dispense ozone continuously and homogeneously at different concentrations and exposure time, in 2 kg aliquots of durum wheat. The optimal conditions, which do not affect chemical and rheological parameters of durum wheat, semolina and pasta, were identified (55 g O₃ h^?1 for 6 h). The measured mean reductions of DON and DON-3-Glc in ozonated wheat were 29% and 44%, respectively. Ozonation also produced a significant (p < 0.05) reduction of total count (CFU/g) of bacteria, fungi and yeasts in wheat grains.     

Effect of germination and dehulling on functional properties of legume flours

The functional properties of flours derived from selected legumes were studied before and after dehulling of the germinated seeds. Ungerminated seeds were used as the control. The chosen legumes were green gram (Phaseolus aureus), cowpea (Vigna catjang), lentil (Lens culinaris) and bengal gram (Cicer arietinum). Dehulled samples had a higher protein solubility compared with germinated and control samples. The bulk densities of germinated and dehulled legume flours were lower compared to control. Germination increased water absorption capacities of legume flours from 1226, 1285, 974 and 1362 g kg^?1 to 1481, 1433, 1448 and 1517 g kg^?1 in green gram, cowpea, lentil and bengal gram, respectively. Fat absorption capacities increased in germinated samples (1130, 1242, 920 and 837 g kg^?1) as against 900, 993, 857 and 788 g kg^?1 at ambient conditions for green gram, cowpea, lentil and bengal gram, respectively. On dehulling, the fat absorption capacities of samples were reduced and the differences were statistically significant. The emulsification capacities of control samples ranged from 55 to 193 ml oil emulsified per gram of sample. On germination and dehulling, the emulsification capacities, activities and stabilities of samples increased significantly. There were increases in foaming capacities and reduction in foam stabilities of all the samples investigated on germination and dehulling. Thus, the study indicated that germination and dehulling improved the functional properties of legumes. Copyright © 2006 Society of Chemical Industry     

Effect of sourdough fermentation on stabilisation,and chemical and nutritional characteristics of wheat germ

Lactic acid bacteria strains were identified from wheat germ by 16S rRNA partial sequencing, subjected to RAPD-PCR typing and screened. Lactobacillus plantarum LB1 and Lactobacillus rossiae LB5 were used as starters to produce sourdough fermented wheat germ (SFWG). The chemical and nutritional characteristics of SFWG were compared to those of the raw wheat germ (RWG). Lipase activity in SFWG was ca. 2.6-fold lower than that found in RWG. As shown by SPME/GC/MS analysis, most of the volatile compounds derived from lipid oxidation during storage (40 days) were at markedly lower levels in SFWG compared to RWG. Fermentation of wheat germ increased of ca. 50% the concentration of free amino acids. Glu markedly decreased in SFWG, due to its conversion in GABA. The concentration of the anti-nutritional factor raffinose also decreased in SFWG. The in vitro protein digestibility, the concentration of total phenols, phytase and antioxidant activities were increased by fermentation.     

Effect of high pressure processing on wheat dough and bread characteristics

Microbial, physical and structural changes in high pressured wheat dough were studied as a function of pressure level (50-250 MPa) and holding time (1-4 min). Thereafter, selected conditions of high hydrostatic processing (HPP) were applied to bread dough and the technological quality of the obtained breads was studied. The effect of HPP on wheat dough was investigated by determining microbial population (total aerobic mesophilic bacteria, moulds and yeasts), color and mechanical and texture surface related dough parameters (cohesiveness, adhesiveness, hardness and stickiness). HPP reduced the endogenous microbial population of wheat dough from 10⁴ colony forming units/g (CFU) to levels of 10² CFU. HPP treatment significantly (P < 0.05) increased dough hardness and adhesiveness, whereas treatment time reduced its stickiness. Scanning electron micrographs suggested that proteins were affected when subjected to pressure levels higher than 50 MPa, but starch modification required higher pressure levels. HPP treated yeasted doughs led to wheat breads with different appearance and technological characteristics; crumb acquired brownish color and heterogeneous cell gas distribution with increased hardness due to new crumb structure. This study suggests that high hydrostatic processing in the range 50-200 MPa could be an alternative technique for obtaining novel textured cereal based products.     

水解度对麦胚清蛋白酶解物功能特性和抗氧化力影响

利用碱性蛋白酶限制性酶解麦胚清蛋白,研究不同水解度(degree of hydrolysis,DH)酶解物的溶解性、乳化性等功能特性,及对DPPH自由基和羟自由基清除等抗氧化能力。实验结果表明,水解后清蛋白酶解物的溶解性得到改善,DH越高溶解性越好。DH为8.34%时,等电点处的溶解度从未水解时的49.52%提高到74.09%。而乳化性和乳化稳定性随DH的增加而降低。当DH低于7.54%时,酶解物对DPPH自由基和对羟自由基的清除率随DH的提高而增强。浓度为100 mg/mL,DH为7.54%时的酶解物对DPPH自由基清除率达到59.68%。浓度为5 mg/mL时,DH为7.54%时的酶解物对羟自由基清除率达50.23%。      

微波预处理对热诱导小麦面筋蛋白凝胶性质和微观结构的影响

研究微波预处理对热诱导小麦面筋蛋白凝胶性质和微观结构的影响。结果表明,当微波条件为700 W功率,处理时间90 s时,热诱导小麦面筋蛋白凝胶强度和持水性达到最大值158.6 g/cm~2和83.13%,比对照组分别提高83.4%和162%,此时凝胶中非冻结水的比例也显著提高。随着微波功率从70 W增加到700W,微波处理时间从10 s增加到90 s,热诱导小麦面筋蛋白凝胶的表面疏水性逐渐降低。微波预处理还显著增大了热诱导小麦面筋蛋白凝胶体系中的疏水相互作用,疏水相互作用的贡献从0.85 g/L增大到1.69 g/L。微波预处理的热诱导小麦面筋蛋白凝胶具有更为致密、均匀的微观三维网络结构。     

谷氨酰胺转胺酶对谷朊质构和流变性质的影响

谷朊是淀粉加工的重要副产品。为了提高谷朊产量和改善谷朊性质,在制备谷朊的过程中,向面浆中加入微生物转谷氨酰胺酶(MTG)。结果表明,随着酶量的增加,谷朊的蛋白含量提高了3.98%。湿面筋的延伸性和回复性随酶量的增加逐渐减小。通过谷朊蛋白质分子羧基含量的测定和蛋白质分子间相互作用力的分析,在MTG作用100min后蛋白分子的羧基含量上升,蛋白质之间疏水相互作用明显减弱。研究表明,在微生物转谷氨酰胺酶(MTG)作用下谷朊的性质产生了明显的变化。     

Effect of xylitol on wheat dough properties and bread characteristics

The aim of the experiment was to evaluate the effect of xylitol on wheat dough properties and bread qualities. The results showed that peak viscosity of bread flour containing 20% xylitol was about 12.59% higher than that of the control. The development time and stability time of dough containing 5% xylitol were 2.55 and 1.62 min longer than those of the control, and the drop value decreased from 454 FU to 359 FU. The extensibility of dough containing 10% xylitol was 21 mm longer than that of the control. The maximum resistance and energy area showed an increasing trend. Scanning electron microscopy images showed a discontinuous gluten matrix in which starch granules were not covered completely with gluten when containing xylitol. The springiness of bread with 10% xylitol was increased by 10.6% compared with that of the control, while the hardness was decreased by 21.5%. The bread added 10% and 15% xylitol had higher scores than the control.     

Effect of genotype,environment, and their interaction on phytochemical compositions and antioxidant properties of soft winter wheat flour

The effect of genotype (G), growing environment (E), and their interaction (G × E) on the antioxidant properties and chemical compositions were investigated using the flour samples of 10 wheat varieties grown in four different locations in Maryland. Lutein content of wheat flour ranged from 0.10 to 0.69 μg/g, and α-tocopherol ranged from 0.12 to 0.83 μg/g. Total carotenoids were primarily affected by E (45.7%), while G × E interaction had a larger effect on the level of total tocopherols (71.6%). E had the largest effect on antioxidant activity against oxygen, hydroxyl, and ABTS^·+ radicals. G had the least influence on the measured phytochemicals and antioxidant activity assays. Total carotenoids had a significant correlation with average low air temperature (r = 0.359, p < 0.01) as well as precipitation level (r = 0.214, p < 0.01). ABTS^·+ radical scavenging capacity had a positive correlation with average air temperature (r = 0.705, p < 0.01), while hydroxyl radical scavenging capacity had a negative correlation with temperature (r = −0.269. p < 0.01). These results show that environment, genotype, and their interaction could influence the levels of lipophilic antioxidants and antioxidant activities of wheat flour.     

Effect of gamma irradiation on microbial load and quality characteristics of minced camel meat

The effect of gamma irradiation on microbial load, chemical and sensory characteristics of camel meat has been evaluated. Camel meat was irradiated at doses of 0, 2, 4 and 6 kGy of gamma irradiation. Irradiated and non-irradiated meat was kept in a refrigerator (1–4 °C). General composition and sensory evaluation of camel meat was done two days after irradiation, whereas, microbiological and chemical analysis was done immediately after irradiation and throughout the storage periods. The results indicated that all doses of gamma irradiation reduced the total mesophilic aerobic plate counts (TPCs) and total coliforms of camel meat. Thus, the microbiological shelf-life of camel meat was significantly extended from less than 2 weeks (control) to more than 6 weeks (samples irradiated with 2, 4 or 6 kGy). No significant differences in moisture, protein, fat, thiobarbituric acid (TBA) values, total acidity and fatty acids of camel meat were observed due to irradiation. There were slight effects of gamma irradiation in both total volatile basic nitrogen (VBN) and lipid oxidation values in camel meat. Sensory evaluation showed no significant differences between irradiated and non-irradiated camel meats.     

Impact of combined ascorbic acid/CaCl2, hydrogen peroxide and ultraviolet light treatments on structure,rheological properties and texture of fresh-cut pear (William var.)

This work aimed to evaluate and correlate rheological properties (dynamic oscillatory, creep/recovery and double compression tests), texture (sensory evaluation) and structure (optical and transmission electron microscopy observations) of fresh-cut pear as affected by ascorbic acid/CaCl₂ dipping, hydrogen peroxide and short-wave ultraviolet light radiation (UV-C). All pear samples showed a solid behavior (G′ > G’’), but both dynamic moduli decreased in response to the treatments. For treated tissues, the instantaneous elastic (J₀) and the retarded (J₁, J₂) compliances increased, while the steady-state viscosity (η_N) and all mechanical parameters decreased. PLS regression models revealed that texture could be well explained by rheological properties. Deformability modulus (E_d) was positively correlated to sensory fracturability and hardness and negatively correlated to juiciness. J₀, J₁ and J₂ were negatively related to sensory hardness. Compression and creep parameters evidenced changes in structure (mainly rupture of membranes, degradation of middle lamella and cell walls) of surface tissues.     

Effect of an enzyme preparation on wheat flour and dough color, mixing, and test baking

Bleaching flours with natural rather than chemical extracts is attractive because it reduces risks upon exposure and appeals to natural food consumers. This paper reports effects of a commercial proprietary blend of ‘natural’ bleaching enzymes on wheat flour and dough color, mixing behavior and test bake performance. Enzyme preparation did not improve whiteness (L*) and yellowness (b*) of flour system, but benzoyl peroxide sharply reduced b*. For whole wheat flour dough, L* increased for enzyme-treated dough after 2-h resting, ending higher than benzoyl peroxide and control dough. Yellowness increased in enzyme-treated dough. When enzyme application was during milling, resulting whole wheat flour dough had much higher L*. Mixograms of flours with increasing enzyme concentration showed severe dough weakness and rapid breakdown. Dialysis of the enzyme preparation in 3500 molecular weight cutoff (MWCO) tubes and freeze-drying prior to flour application recovered dough strength. l-cysteine in the enzyme mix was thought to adversely affect dough strength, and dialysis helped recover dough strength. However, pup loaf baking with dialyzed enzyme showed some loss of baking characteristics (loaf volume, loaf weight, and proof height) over the control. Although the natural enzyme extract addition enhanced whiteness for whole wheat dough, its effects on dough and baking properties were not favorable.     

Inactivation of Escherichia coli O157:H7 and Salmonella in Apple Cider and Orange Juice Treated with Combinations of Ozone, Dimethyl Dicarbonate, and Hydrogen Peroxide

ABSTRACT: Inactivation of Escherichia coli O157:H7 and Salmonella in apple cider and orange juice treated with ozone in combination with antimicrobials was evaluated. E. coli O157:H7 or Salmonella was suspended in cider and orange juice, and ozone was pumped into juices (4°C) containing dimethyl dicarbonate (DMDC; 250 or 500 ppm) or hydrogen peroxide (300 or 600 ppm) for up to 90 min (study 1) or 60 min followed by 24-h storage at 4°C (study 2). Study 1: No combination of treatments resulted in a 5-log colony-forming units (CFU) /mL reduction of either pathogen. Study 2: All combinations of antimicrobials plus ozone treatments, followed by refrigerated storage, caused greater than a 5-log CFU/mL reduction, except ozone/DMDC (250 ppm) treatment in orange juice. Ozone treatment in combination with DMDC or hydrogen peroxide followed by refrigerated storage may provide an alternative to thermal pasteurization to meet the 5-log reduction standard in cider and orange juice.     

Effects of germination time on the structural,physicochemical and functional properties of brown rice

Germinated brown rice (GBR) is a gluten-free food raw material. Its tissue structure, physicochemical properties and functional properties depend on the germination time. In this study, rapid viscosity analyses, differential scanning calorimetry and X-ray diffraction et al were used to analyse the structural, physicochemical and functional changes in brown rice (BR) during germination. Gamma-aminobutyric acid (GABA), total phenolic compound, glutathione (GSH) and amino acid contents increased during germination. GBR exhibited the highest GSH (22.70 mg per 100 g) and amino acid (8.02 mg per 100 g) contents at 24 h and the highest GABA content (253.35 mg per 100 g) at 36 h. Furthermore, BR germinated for 36 h showed greater enthalpy (ΔH) than ungerminated BR. Although GBR showed less crystallinity than ungerminated BR, germination did not change the crystalline structure type of starch (A-type). These results inform choices of the appropriate applications of GBR to promote its utilisation in the food industry.