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1.
The oxidative stability was examined in whole wheat bread packed in modified atmosphere (nitrogen) using vacuum grade plastic bags and stored for up to 5 weeks. Small, but significant, differences in oxidative stability developed with time for whole wheat bread crumb and crust. The samples were evaluated by direct electron spin resonance (ESR) spectroscopy for detection of free radicals, peroxide value (POV), overall antioxidative capacity using Trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays, and by the content of tocopherols as determined by HPLC. The overall antioxidative capacity was reduced during storage with an accumulation of lipid hydroperoxides peaking after 2-3 weeks of storage. Bread crust was generally found to be more oxidative stable when compared to crumb. Quality of bread with extended shelf life may accordingly be improved minimising oxidation. 相似文献
2.
Bread staling is a very complex phenomenon that is not yet completely understood. The present work explains how the electrical impedance spectroscopy technique can be utilized to investigate the effect of staling on the physicochemical properties of wheat bread during storage. An instrument based on electrical impedance spectroscopy technique is developed to study the electrical properties of wheat bread both at its crumb and crust with the help of designed multi-channel ring electrodes. Electrical impedance behavior, mainly capacitance and resistance, of wheat bread at crust and crumb during storage (up to 120 h) is investigated. The variation in capacitance showed the glass transition phenomenon at room temperature in bread crust after 96 h of storage with 18% of moisture in it. The resistance changes at bread crumb showed the starch recrystallization during staling.Industrial relevanceSimultaneous measurement of moisture content, glass transition and starch recrystallization is possible with the designed instrument without disturbing the experimental set-up. Thus, the present work is going to help manufacturers and researchers to understand the bread staling phenomenon at crust and crumb without opting very complex instrumental procedures. 相似文献
3.
以开麦21为原料,对其进行鼓风干燥和调质处理,使其水分含量分别为12.5%,9.5%,7.7%和5.9%,在35℃下密封储藏,研究其储藏过程中生活力、电导率、过氧化氢酶活动度、湿面筋含量、干面筋含量和面筋吸水率的变化,探讨高温密闭储藏下小麦的水分含量与其储藏品质变化的规律。结果表明:35℃条件下,水分含量高的小麦其生活力、过氧化氢酶活动度、湿面筋含量和面筋吸水率降幅大;水分含量为7.7%的小麦电导率增幅最小。 相似文献
4.
以感官、微生物和化学变化为指标,探讨了水分含量对淡腌大黄鱼贮藏性的影响。结果表明,水分含量为60%±1%、55%±1%、50%±2%的样品货架期分别是5、9、11d。3组样品货架期终点时菌落总数(TVC)值约为8lg(cfu/g),总挥发性盐基氮(TVB-N)值约为30mg/100g,硫代巴比妥酸反应物(TBARS)值在贮藏期间均出现峰值。贮藏初期菌相比较单一,共检测到4种细菌,贮藏过程中菌相发生变化,货架期终点时仅残存2种细菌,分别为沃氏葡萄球菌(Staphylococcus warneri)和洛菲不动杆菌(Acinetobacter lwoffii)。 相似文献
5.
V. Lampignano J. Laverse M. Mastromatteo M.A. Del Nobile 《Food research international (Ottawa, Ont.)》2013,50(1):369-376
In this study, breads varying in yeast content and therefore leading to distinct cellular structures are investigated. Firstly, X-ray microtomography is used to characterize not only the final cellular structure, but also the process of development of microstructure during the fermentation stage. With μCT, image analysis of the full 3-D microstructure, measuring the size, shape, networking/connectivity and distribution of various phases was possible. These measurements represent the full 3-D microstructure, which is not always possible by 2-D image analysis using statistical techniques. Secondly, the textural properties of the baked bread were obtained by compression tests and finally, the sensorial quality of the final product is also evaluated and correlated with the above properties. Results showed that an increase of the yeast content increased the percentage volume of pores and decreased the force required for compression of the bread sample and the tenacity. Moreover, a larger quantity of smaller sized pores led to a firmer bread structure. Regarding the sensorial properties, none of the investigated microstructural parameters were significantly correlated with the overall quality of the bread. In fact, the overall quality was more strongly affected from other parameters such as odor and appearance attributes. 相似文献
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7.
Safe storage time of high moisture wheat 总被引:1,自引:0,他引:1
Karunakaran C Muir WE Jayas DS White ND Abramson D 《Journal of Stored Products Research》2001,37(3):303-312
Deterioration rates were determined for 15-19% moisture content (m.c., wet basis) wheat (Triticum aestivum L. cv. 'Barrie') stored at constant temperatures or with a step decrease in storage temperatures. Deterioration rates were determined by measuring germination capacity of the grain and respiration rates of grain and microorganisms. Safe storage time was defined as the time for germination to decrease to 90%. Safe storage times of 19% m.c. wheat stored at constant temperatures ranged from 2.5 d at 30 and 35 degrees C to 37 d at 10 degrees C. Deterioration rates of 19% m.c. wheat stored with a step decrease in storage temperatures (35-25, 30-20, 25-20, and 20-15 degrees C) were determined and safe storage times were satisfactorily predicted. Safe storage times of 17% m.c. wheat were 5, 7, and 15 d at 35, 30, and 25 degrees C, respectively. Respiration rates and germination percentages of 15 and 16% m.c. wheat stored at 25 degrees C remained constant for 70 d. The respiration rates of 17-19% m.c. wheat at 25 degrees C increased while the germination percentages decreased with storage time. Germination dropped from 98 to 92-89% when the dry matter losses were about 0.05% and visible mould occurred when the dry matter losses were about 0.1% in 17-19% m.c. wheat. Safe storage times of 17% m.c. wheat stored at 35-25 degrees C were compared with those determined in similar previous work with cultivars 'Domain' and 'Katepwa'. 'Domain' had the longest and 'Barrie' had the shortest storage times. 相似文献
8.
The main objective of the study was to assess the influence of moisture content on short infrared absorptivity of bread dough. Weight loss, surface temperature and short to medium infrared absorptivity of dough were measured in a series of radiant heating experiments. A strong positive correlation between surface temperature and total heat flux absorbed by the dough samples was observed. The variation of infrared absorptivity of the dough is explained with the state of the water in the samples - vapor or liquid. 相似文献
9.
Two baking times (9 and 24 min) and storage temperatures (4 and 25 °C) were used to explore the impact of heat exposure during bread baking and subsequent storage on amylopectin retrogradation, water mobility, and bread crumb firming. Shorter baking resulted in less retrogradation, a less extended starch network and smaller changes in crumb firmness and elasticity. A lower storage temperature resulted in faster retrogradation, a more rigid starch network with more water inclusion and larger changes in crumb firmness and elasticity. Crumb to crust moisture migration was lower for breads baked shorter and stored at lower temperature, resulting in better plasticized biopolymer networks in crumb. Network stiffening, therefore, contributed less to crumb firmness. A negative relation was found between proton mobilities of water and biopolymers in the crumb gel network and crumb firmness. The slope of this linear function was indicative for the strength of the starch network. 相似文献
10.
将同一小麦样品进行人工调节水分,然后在不同水分条件下,用小麦硬度指数仪进行测量小麦硬度指数,并对结果进行分析,探讨水分对小麦硬度指数的影响. 相似文献
11.
Qingjie Sun Yan Xing Liu Xiong 《International Journal of Food Science & Technology》2014,49(4):1159-1167
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. 相似文献
12.
Bert Lagrain Pedro Leman Hans Goesaert Jan A. Delcour 《Food research international (Ottawa, Ont.)》2008,41(8):819-827
Thermostable amylases [Bacillus subtilis α-amylase (BSuA) and B. stearothermophilus maltogenic amylase (BStA)] with different modes of action and impacts on firming properties were added during straight-dough bread making. BSuA continuously degraded the starch fraction during bread making. Its action resulted in larger gas cells than in control bread, but did not change initial firmness. In contrast to BSuA, BStA mainly degraded starch at the end of the baking phase and during bread cooling, which caused little if any impact on bread crumb texture. However, it led to higher initial firmness readings than for the control breads. Neither BSuA nor BStA were inactivated during bread making. The results evidence that starch properties have a large impact on bread crumb structure and initial firmness and are highly influenced by the mode of action of the enzyme. 相似文献
13.
Although several empirical models are available in the literature to predict density in solid matrices, only a very limited number of theoretical models have been reported. So far, no model considered the possible variation in the initial air volume existing at the beginning of the drying process. In this contribution, a theoretical model to predict bulk density of dried materials was built by considering two mechanisms that might occur during drying processes. These mechanisms are represented by collapse and shrinkage functions. The predictions obtained by this theoretical model were extensively validated with experimental data published by several independent groups for different food products dried with different technologies. In all these cases, the model gave excellent agreement with the experimental data regardless the topology of the curve bulk density versus moisture content. The model was also compared with other published models. The result of this comparison revealed that the errors resulting from the predictions obtained by the present model are among the smallest. Shrinkage and collapse functions were used to analyze the mechanisms by which bulk density varies during air-drying and freeze-drying. The model showed that both shrinkage and collapse phenomena are dramatically involved during air-drying. However, in the case of freeze-drying, no collapse is observed and only partial shrinkage is taking place. Hence, the present model can be used as a tool to predict the bulk density with excellent accuracy, to understand the dynamic mechanisms involved during drying. Moreover, this model can be incorporated to other models involving the variation of density as a function of moisture. 相似文献
14.
Mycotoxins, ergosterol, and odor volatiles in durum wheat during granary storage at 16% and 20% moisture content 总被引:5,自引:0,他引:5
Eleven-kilogram parcels of durum wheat (Triticum durum L. cv. Melita) at 16% and 20% initial moisture content (m.c.) were kept in storage in a Manitoba farm granary for 20 weeks (May-September 2000) to determine changes in storage quality indicators and mycotoxin production. Temperature, moisture, CO2 levels, ergosterol content, odor volatiles, microfloral infection, and levels of major mycotoxins were monitored. Ochratoxin A and citrinin reached mean levels of 6.5 and 11.6 mg/kg, respectively, by 20 weeks at 20% m.c., but were absent at 16% m.c., and no other mycotoxins were found. Penicillium species were the predominant microflora. Ergosterol levels remained between 3.9 and 8.4 mg/kg at 16% m.c., but increased from 3.9 to 55.5 mg/kg at 20% m.c. during the 20-week trial period. A 12-element metal-oxide chemosensor array was used to monitor odor volatile evolution. Nine of the 12 sensors were able to track odor volatile changes at 20% and could consistently distinguish between volatiles from the two moisture treatments. Signals from these nine chemosensors showed a good correlation with ochratoxin A formation at 20% m.c. with r values between 0.84 and 0.87. Signals from two of these nine sensors also correlated well with citrinin formation (r=0.83) and very well with ergosterol production (r=0.98). 相似文献
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16.
Moisture transmission properties are most important for fabric comfort. We have studied the moisture transmission properties of the plain-woven fabric produced with polyester–viscose-(PV) blended yarns. PV-blended yarns of varying blend proportion, yarn count and twist levels have been used for fabric manufacture. A three-variable Box and Behnken factorial design technique has been used to study the interaction effects of the above variables on the aforesaid characteristics of fabrics. The interactive effect of these three variables on the air permeability, water vapour permeability, in-plane wicking and vertical wicking of PV-blended fabrics has been studied and the response surface equations for all the properties have been derived; also, the design variables have been optimized for all the moisture transmission-related properties. Most of the moisture transmission characteristics were found to be affected significantly by blend proportion, count and twist levels at 95% level of significance with the present variables. 相似文献
17.
To investigate the impact of baking conditions on staling kinetics and mechanical properties, pan breads were baked at 180 °C/34 min and 220 °C/28.6 min using a ventilated oven and metallic moulds. After baking, bread slices were stored with and without crust at 15 °C in hermetic boxes for 9 days. This investigation provides a textural and physical analysis by examining the Young's modulus, crumb density and crust/crumb ratio during storage. In order to understand the relationship between firmness and moisture content, a moisture profile and a Young's modulus profile were determined during the storage of bread. To fit the staling, a first order model was used. It was found that the kinetics were faster for samples baked with a fast heating rate than for those baked with a slow heating rate. Moreover, the staling rate of bread stored with crust was faster than for bread without crust and the outer crust area staled more rapidly than the centre of the bread slice. These results suggest that the firming of the crumb is related to moisture distribution between the crumb and crust and to the impact of local baking conditions on local firmness. 相似文献
18.
Abstract The geometric dimensions, weight of 1000 fruits, bulk density and specific heat of chilli (variety balijuri, Mymensingh local) were determined experimentally at the moisture contents of 5.14, 13.94, 26.47, 40.69, 58.94 and 73.03% (wet basis). Length of chilli fruit was found to be linearly dependent on moisture content. Chillies pose flat shape from the moisture contents 5.14 to 40.69% (wet basis) and in this moisture range the width and thickness were linearly dependent on moisture content. Above the moisture content of 40.69%, chilli fruit remained round in shape and fruit diameter was also increased linearly with the increase of moisture content. The weight of 1000 fruits, bulk density and specific heat appeared to be linearly dependent on moisture contents and these properties increased with the increase of moisture contents from 5.14 to 73.03% (wet basis). 相似文献
19.
Guénaelle Leray Bonastre OlieteSandra Mezaize Sylvie ChevallierMarie de Lamballerie 《Journal of food engineering》2010
Empirical and fundamental rheological measurements were made on fresh and frozen dough to study the effects of freezing and frozen storage conditions. Frozen dough was stored at two different temperatures, −18 °C and −30 °C, and for 1, 7 and 28 days. Four dough formulations were tested: a standard wheat dough, a fibre-enriched wheat dough, a standard gluten-free dough and a gluten-free dough containing amaranth flour. No yeast was used in any formulation. The wheat dough is more affected by freezing and by the first days of storage whereas the gluten-free dough is more affected by a longer storage time. A storage temperature of −30 °C alters dough rheological properties more than a storage temperature of −18 °C. The addition of dietary fibres to the wheat dough increases its resistance to freezing and frozen storage. The addition of amaranth flour to gluten-free dough also increases its resistance to freezing but decreases its resistance to storage conditions. 相似文献
20.
糙米储藏水分对糊化特性的影响 总被引:1,自引:0,他引:1
对13.5%、14.5%、15.5%、16.5%水分条件下储藏的糙米进行定期的RVA测定,糙米放入温度设定为25℃的恒温箱中储藏,储藏时间为6个月,每30d检测一次。结果表明:不同水分储藏样品的峰值粘度随着储藏时间延长不断增加,储藏水分越高,峰值粘度上升越快;水分、时间对峰值粘度影响极显著(p〈0.01);峰值粘度与储藏时间、水分呈极显著二元线性关系。储藏样品的最低粘度随着储藏时间延长不断增加,水分含量越高最低粘度越高;水分、时间影响极显著;最低粘度与储藏时间、水分呈极显著二元线性关系。不同水分储藏样品的崩解值随着储藏时间延长变化不同;水分、时间影响显著性分别为0.029、0.000;回归方程显示,低水分储藏崩解值随着储藏时间延长而升高,高水分储藏崩解值与时间则成显著一元二次方程的关系。水分、时间对最终粘度影响显著性为0.000;最终粘度随时间、水分变化经曲线拟合呈显著二元线性关系,回归方程显著。储藏期间,糙米回生值随时间延长显著上升,储藏后期趋于下降;方差分析显示时间对回生值影响极显著,水分影响不显著,不同水分样品与储藏时间均呈极显著一元二次方程关系。含水率越高,糙米食味品质保持越好。 相似文献