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1.
Despite much research, bread crumb firming during storage and amylase anti-staling properties are still ill understood. We present a coherent view on the topic based on literature, experimental data, and food polymer science-related concepts. During bread storage, the gelatinised starch (amylopectin) network, present in soft, fresh bread, is gradually transformed into an extensive, partially crystalline, permanent amylopectin network, with amylopectin crystallites acting as junction zones. This network increasingly accounts for the bulk rheological behaviour of aging bread crumb. Furthermore, as amylopectin retrogradation proceeds, moisture migration within the crumb structure occurs, and more and more water is immobilised within amylopectin crystallites. The crystalline hydrate water can no longer plasticise the different networks, which goes hand in hand with increased crumb firmness and decreased crumb resilience, due to a less flexible gluten network. The efficiency of anti-staling amylases can be related to the extent they limit the formation and the strength of the permanent amylopectin network, and the water immobilisation. Conventional alpha-amylases weaken the amylopectin network by cutting the long polymer chains connecting the crystalline regions, but have little effect on amylopectin recrystallisation. In contrast, maltogenic alpha-amylase primarily shortens the amylopectin side chains, thus hindering amylopectin recrystallisation, and the concomitant network formation and water immobilisation.  相似文献   

2.
The ability of oat foods to lower serum cholesterol and post-prandial blood glucose concentrations has been linked to the physicochemical properties of the bioactive component, mixed linkage β-glucan. Oat foods frequently need to be shipped or stored prior to analysis and β-glucan characteristics may change over time. Reductions in β-glucan solubility or molecular weight lead to lower viscosity development which decreases bioactivity. Impact of freezing and freeze drying conditions on the β-glucan physicochemical characteristics in oat bran bread and porridge were studied. Two in vitro digestibility methods were used to produce physiological extracts and the results were compared. The β-glucan molecular weight, solubility and viscosity for oat bread stored at room temperature were unchanged for 3 days, followed by a gradual decline in these parameters. The extract viscosity for bread decreased significantly after freezing at −80 °C and freeze drying after freezing at −18 and −80 °C, whereas freezing in liquid nitrogen did not significantly influence viscosity. Freezing of oat bran porridge did not affect extract viscosity, but freeze drying resulted in reduction of extract viscosity compared to the fresh porridge. Freezing and freeze drying did not dramatically affect the molecular weight or solubility of β-glucan in either product. The rapid visco analyzer was more effective and reliable for sample digestion than when physiological extraction was conducted in the shaking water bath. Generally, freezing at −18 °C or by submersion in liquid nitrogen maintained the physicochemical characteristics of β-glucan in food products either for commercial products or subsequent analysis.  相似文献   

3.
Under Mediterranean environments, farmers usually prefer to sow barley rather than wheat as it is generally believed that barley yields more under stressful conditions. As terminal stresses such as high temperature and water are common constraints in Mediterranean regions, higher grain weight stability may confer a clear advantage in order to maintain higher yields. The objective of the present study was to compare the stability in terms of grain weight and its components for barley, bread wheat, and durum wheat, exploring a wide range of nitrogen and water availabilities in experiments conducted in a Mediterranean region. Grain weight ranged from 23.8 to 47.7 mg grain−1, being higher for durum wheat than barley and bread wheat. Durum wheat presented higher variability both in maximum grain filling rate and duration of grain filling period than bread wheat or barley. The three species responded similarly in terms of grain nitrogen content to changes in the environmental conditions explored. It is concluded that in terms of grain weight barley is as stable as bread wheat. However, durum wheat presented a lower stability than barley and bread wheat.  相似文献   

4.
The contribution of gliadins to the baking performance of wheat has been widely discussed. In the present study we report the properties of the flours of fifteen transgenic wheat lines with γ-gliadins down-regulated by RNAi. Technological properties were assessed by sodium dodecyl sulfate sedimentation (SDSS) test, and rheological properties were characterized during mixing using the Mixolab®. Changes in the proportions of gluten proteins, with significant increases of glutenins, were observed in transgenic lines. These changes did not affect the SDSS test in most of the transgenic lines. The dough strength of some transgenic lines was reduced as determined by the Mixolab®. Changes in the starch behavior were also observed in the transgenic lines, in which lower values of torque were observed at the C3, C4 and C5 points of the mixing curve. The results reported here are important in understanding the role of γ-gliadins in the bread-making quality of flours.  相似文献   

5.
Enzymes from wheat bran and germinated wheat involved in the degradation of arabinoxylan and arabinoxylooligosaccharides were investigated. Fourp-nitrophenyl-α-l-arabinofuranoside hydrolysing activities (ArafI-IV) and threep-nitrophenyl-β-d-xylopyranoside hydrolysing activities (XylpI-III) were identified in wheat kernels and germinating wheat. Two of these activities, ArafI and XylpII, were purified about 10 000-fold from wheat bran. Both enzymes were inactive towards polymeric arabinoxylan. ArafI produced no arabinose but some xylose from arabinoxylooligosaccharides, while XylpII gave only xylose upon incubation with this substrate. An arabinoxylan arabinofuranohydrolase (AXH) was found in wheat bran and germinated wheat. This enzyme was active towards the polymeric substrate, but was unable to hydrolysep-nitrophenyl-α-l-arabinofuranoside. TheMrs of these enzymes were determined by size exclusion chromatography and were in the range of 40–50 000, except for ArafIII, for which aMrof 104 000 was determined. During germination, the levels of these enzymes increased markedly between the third and fifth day, after which some of them decreased again by the seventh day. ArafI-IV were inhibited strongly by arabinonic acid-γ-lactone, while xylonic acid-γ-lactone was a good inhibitor of XylpI-III. The latter lactone also inhibited ArafI. Neither of these lactones inhibited AXH. Endoxylanase activity was demonstrated but not quantified.  相似文献   

6.
Inhibition of α-glucosidase and pancreatic α-amylase is one of the therapeutic approaches for delaying carbohydrate digestion, resulting in reduced postprandial glucose. The aim of this study was to evaluate the phytochemical analysis and the inhibitory effect of various cinnamon bark species against intestinal α-glucosidase and pancreatic α-amylase. The results showed that the content of total phenolic, flavonoid, and condensed tannin ranged from 0.17 to 0.21 g gallic acid equivalent/g extract, from 48.85 to 65.52 mg quercetin equivalent/g extract, and from 0.12 to 0.15 g catechin equivalent/g extract, respectively. The HPLC fingerprints of each cinnamon species were established. Among cinnamon species, Thai cinnamon extract was the most potent inhibitor against the intestinal maltase with the IC50 values of 0.58 ± 0.01 mg/ml. The findings also showed that Ceylon cinnamon was the most effective intestinal sucrase and pancreatic α-amylase inhibitor with the IC50 values of 0.42 ± 0.02 and 1.23 ± 0.02 mg/ml, respectively. In addition, cinnamon extracts produced additive inhibition against intestinal α-glucosidase and pancreatic α-amylase when combined with acarbose. These results suggest that cinnamon bark extracts may be potentially useful for the control of postprandial glucose in diabetic patients through inhibition of intestinal α-glucosidase and pancreatic α-amylase.  相似文献   

7.
The objective of this study was to determine effect of storage time, storage temperature and addition of fibre on sensory quality, state of water, microstructure and texture of bread and dough.  相似文献   

8.
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9.
In recent years, the Israeli wheat industry has suffered from quality problems that endangered the possibility of growing bread wheat in Israel. In addition to relying upon grain protein and test weight, the Israeli wheat market has therefore begun using the gluten index (GI) test method. To shed new light on wheat grain quality determinations, wheat grain samples were analyzed for GI and other quality parameters such as dry and wet gluten, SDS-sedimentation, and loaf volume. In many cases, low-GI grains exhibited good dough and bread quality. This could be attributed to the difference in GI values of the wheat versus the corresponding flour. Hence, milling plays a major role in GI determination. Furthermore, grain and white flour GI values did not correlate with other accepted quality parameters, such as SDS-sedimentation and loaf volume. Therefore, it is suggested that the GI be used with caution, and that the addition of other methods can improve wheat quality determination.  相似文献   

10.
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11.
A total of 17 cropping schedules for the winter (rabi)–summer (zaid) season of north Indian plains were compared for the yield and economics of produce per hectare of land. In comparison to wheat, the sucker-planted mint crop was estimated to bring in a 32% higher income. The co-cultivation of wheat with sucker-planted mint gave 15% more productivity over wheat alone and 70% over mint alone. The relay cropping of wheat followed by transplanted mint had the highest productivity, 45% higher than that of co-cultivated wheat and mint. The cultivar HD 2285 of wheat (Triticum aestivum L.) and Himalaya/Kosi cultivars of mint (Mentha arvensis L.) were found to fit well in the co-cultivation and relay cropping schedules using wheat and mint crops. The results allowed recommendation of the following rotations for high yield together with resource conservation, permitting intensive agriculture by farmers with small holdings in Indo-Gangetic plains: (1) rice/greengram/blackgram, transplanted basil, wheat+mint, pigeonpea, chickpea, transplanted mint; and (2) pigeonpea, wheat, transplanted mint, rice, transplanted basil, wheat+mint.  相似文献   

12.
Kernel texture (hard vs soft grain) and more subtle within-class variations are known to have a large influence on end-use properties, mostly through the proportion of damaged starch and subsequent water requirement. In this study, quantitative trait loci (QTL) affecting kernel texture and dough rheology in a progeny from a cross between two ‘medium-hard’ wheat cultivars were identified and compared to the QTL locations for both traits. One hundred and sixty-five F7 recombinant inbred lines were studied in three environments in 1999. Kernel texture was estimated by both near infrared reflectance (NIR: HardNIR) and the single-kernel characterisation system (SKCS: HardSKCS). Dough rheology, taken as a predictor of end-use quality, was estimated by the empirical parameters measured by Chopin alveograph. The genetic map for this population consisted of 254 loci quite evenly distributed over the wheat genome. Considering only the QTL which were stable (detected in the three locations) and robust (through bootstrap resampling), five genomic regions were found to influence HardNIR, but only two of them are significant for HardSKCS, which was probably due to a less representative measure of the phenomenon. Eight QTLs were found for rheological traits. Some QTLs for dough rheology co-located with those for hardness or grain protein content, particularly on chromosomes 3A and 5B and close to the unlinked marker Xgwm130. According to trait, individual QTLs explained from 5.4 to 26.6% of the phenotypic variation and when taken together up to 46.0% of the variation.  相似文献   

13.
In the present study, we synthesized and, structurally and functionally characterized a novel α4/7-conotoxin Mr1.7 (PECCTHPACHVSHPELC-NH2), which was previously identified by cDNA libraries from Conus marmoreus in our lab. The NMR solution structure showed that Mr1.7 contained a 310-helix from residues Pro7 to His10 and a type I β-turn from residues Pro14 to Cys17. Electrophysiological results showed that Mr1.7 selectively inhibited the α3β2, α9α10 and α6/α3β2β3 neuronal nicotinic acetylcholine receptors (nAChRs) with an IC50 of 53.1 nM, 185.7 nM and 284.2 nM, respectively, but showed no inhibitory activity on other nAChR subtypes. Further structure-activity studies of Mr1.7 demonstrated that the PE residues at the N-terminal sequence of Mr1.7 were important for modulating its selectivity, and the replacement of Glu2 by Ala resulted in a significant increase in potency and selectivity to the α3β2 nAChR. Furthermore, the substitution of Ser12 with Asn in the loop2 significantly increased the binding of Mr1.7 to α3β2, α3β4, α2β4 and α7 nAChR subtypes. Taken together, this work expanded our knowledge of selectivity and provided a new way to improve the potency and selectivity of inhibitors for nAChR subtypes.  相似文献   

14.
Oat malt is a nutritionally rich ingredient mainly used in a small number of speciality products. The aim of this study was to evaluate the suitability of oat malt in wheat baking. The effect of oat malt on bread and dough properties at levels ranging from 0.5% to 5% was studied and compared with barley and wheat malts. The addition of all malts increased loaf specific volumes. Barley and wheat malts at levels above 2.5% led to a sticky and coarse crumb, but the effect of oat malt on the crumb grain was negligible. Rheological characterisation could not explain the superior baking performance of oat malt, as it increased extensibility and decreased resistance extensively indicating weakening of the extensional properties of the gluten network. The high lipolytic activity may have compensated for the loss of dough strength by improving the surface properties of gas cells. The results show that oat malt can be used in wheat baking to improve the loaf volume and nutritional quality without the detrimental effects associated with the excess amylolytic activity of barley and wheat malts.  相似文献   

15.
α-Conotoxin LvIA is derived from Conus lividus, native to Hainan, and is the most selective inhibitor of α3β2 nicotinic acetylcholine receptors (nAChRs) known to date. In this study, an efficient approach for the production of recombinant α-Conotoxin LvIA is described. Tandem repeats of a LvIA gene fragment were constructed and fused with a KSI gene and a His6 tag in a Escherichia coli (E. coli) expression vector pET-31b(+). The recombinant plasmids were transformed into E. coli and were found to express well. The KSI-(LvIA)n-His6 fusion protein was purified by metal affinity chromatography and then cleaved with CNBr to release recombinant LvIA (rLvIA). High yields of fusion protein ranging from 100 to 500 mg/L culture were obtained. The pharmacological profile of rLvIA was determined by two-electrode voltage-clamp electrophysiology in Xenopus laevis oocytes expressing rat nAChR subtypes. The rLvIA antagonized the α3β2 nAChR subtype selectively with a nano-molar IC50. The rLvIA was analgesic in a mouse hot-plate test model of pain. Overall, this study provides an effective method to synthesize α-conotoxin LvIA in an E. coli recombinant expression system, and this approach could be useful to obtain active conopeptides in large quantity and at low cost.  相似文献   

16.
Zein was recovered from corn distiller's dried grains with solubles (DDGS) by a modified method using 70% (w/w) aqueous 2-propanol (70-IPA) or 70% (v/v) aqueous ethanol (70-EtOH) solvents, and a commercial method using 88% (w/w) aqueous 2-propanol (88-IPA). Yield, purity, and film properties of the isolated zein were determined. The modified procedure extracted two fractions of zeins: a mostly α-zein fraction, and a mostly γ-zein fraction. The modified method increased α-zein yield from 4% to 14%. Enzyme cellulase pretreatment did not improve zein yield, but grinding did. The α-zein fraction showed electrophoretic bands at 40, 22, 19, and 10 kDa, corresponding to α-zein dimer, α1-zein, α2-zein, and δ-zein, respectively. The α-zein of DDGS retained its film forming capability. The α-zein film of unmodified DDGS was cloudy and rough, unlike the clear and smooth films of α-zeins isolated from corn gluten meal and enzyme-treated DDGS.  相似文献   

17.
Traditional AOAC colorimetric procedures for carotenoid analysis are known to lack specificity and accuracy. Newer HPLC methods provide the investigator with a more precise tool for carotenoid quantification in foods and tissues. In the present studies, reverse phase HPLC was utilized to evaluate the - and -carotene content in raw and cooked leaves of lettuce, spinach and winged bean as well as in the carrot root. The vegetables were boiled or steamed and the true retention of - and -carotene in the cooked products was determined. Boiling for 30 minutes resulted in a 53 and 40% loss of -carotene from lettuce and carrots, respectively. Full retention or even an increase in -carotene content in boiled winged bean leaves and spinach was noted. Steaming resulted in very good retention of - and - carotene in all vegetables (83–139% retention). Thus, although cooking procedures (especially boiling) may result in oxidative loss of carotenoids in some vegetables, heat treatment increases the chemical extractability of - and -carotene in others. The presence of carotenoproteins in some vegetables may effect the heat stability of extractability of - and - carotene.  相似文献   

18.
Milling fractions of hull-less barley, and dough and bread with hull-less barley flour (40%) and wheat flour (60%) were analysed in an investigation of how the properties of (1→3, 1→4)-β-glucan were affected by milling, dough formation and bread making. Calcofluor average molecular weight (M¯cf) and molecular weight distribution and the cellotriosyl/cellotetraosyl ratio of the (1→3, 1→4)-β-glucan were determined. Four different hull-less barley samples were milled to produce straight-run white flours, shorts, bran and whole-meal flours. The molecular weight distributions were unimodal for all fractions, and the (M¯cf) range was between 117×104 and 188×104. These parameters were similar for all barleys, although (M¯cf) was somewhat lower in white flour and bran fractions and somewhat higher in shorts and whole-meal. The cellotriosyl/cellotetraosyl ratio (1.5–1.8) was also similar in all fractions. Doughs and breads were made to study how flour type (sifted or whole-meal barley flour), water content, yeast, mixing time and fermentation time affect (1→3, 1→4)-β-glucan. The molecular weight distribution of (1→3, 1→4)-β-glucan was polymodal with two or three populations for all doughs and breads, and the (M¯cf) decreased with increasing mixing and fermentation time. These results indicated that (1→3, 1→4)-β-glucan was degraded by endogenous β-glucanases in the barley and/or wheat flour. The molecular weight was not significantly affected by bread-baking and other factors. After mixing and fermentation the cellotriosyl/cellotetraosyl ratio was about 1.7–1.8 and was thus not significantly different from that of the flour blends. Thus to retain high molecular weight (1→3, 1→4)-β-glucan, which is important for its cholesterol-lowering effect, it is thus important to keep the mixing and fermentation time as short as possible when baking hull-less barley bread.  相似文献   

19.
The GlutoPeak®-Test (GPT) as a rapid small-scale technique was optimized to evaluate the gluten aggregation properties and to predict the loaf volume, on the basis of a multiyear and multilocation analysis of wheat samples, using different solvents. 5 % lactic acid and 1 % sodium chloride displayed significant GPT responses. Relationships between protein content, sedimentation value, GPT parameters and loaf volume were investigated. With 1 % sodium chloride, the torque 15 s before maximum torque (AM) presented the highest correlation with loaf volume of samples from 2013 to 2014 (r = 0.77, r = 0.63, p < 0.001, respectively). A multiple regression analysis indicated that the best prediction of loaf volume was a linear function of protein content and AM, explaining the variation in loaf volume by 63 % and providing an uncertainty of ±39 ml. The accuracy of the validation of the linear function leads to 64 % correct and to 36 % incorrect predictions of the loaf volume. This emphasizes that the application of the linear function of protein content and AM cannot replace the actual measurement of loaf volume, but it could be a useful rapid screening test in breeding for improved baking quality in bread wheat.  相似文献   

20.
Amylolytic and tryptic inhibitors of faba bean extracts were determined by an agar diffusion test. The amylolytic inhibitor had protein characters. Furthermore, water-soluble trypsin inhibitors ofCicer arietinum, Lens esculenta, Lupinus termis, Phaseolus vulgaris, Pisum sativum, Trigonella foenum-graecum andVicia faba which were separated by polyacrylamide gel isoelectric focusing (PAGIF) in thin-layers, showed species specific patterns. Negative staining showed 10 bands for French beans, 9 for fenugreek seeds, 8 for lentils and chickpeas, 7 for peas and 6 for faba beans. Lupin seeds were free from trypsin inhibitors. Treatments (soaking, germination and heat processing) of faba beans reduced the number of trypsin inhibitors in PAGIF patterns, less after soaking and germination, but more after roasting and frying. No inhibitors were detected after cooking.  相似文献   

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