糙米储藏水分对糊化特性的影响

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。     

Effect of seed moisture content on flaxseed (Linum usitatissimum L.) milling and milled product characteristics

BACKGROUND: Research was conducted to determine the effect of seed moisture content on flaxseed milling and milled product characteristics. Flaxseed with 55, 80, and 105 g kg^?1 moisture contents were milled on a centrifugal cutting mill (CCM) configured with a 0.475 and 9.5 kg min^?1 feed rate; a hammer mill configured with a blunt hammer face, 0.35 kg min^?1 feed rate, 3.1 mm screen, and 2,795 m min^?1 hammer tip speed; and a hammer mill configured with a sharp hammer face, 0.35 kg min^?1 feed rate, 2.7 mm screen, and 3,870 m min^?1 hammer tip speed. RESULTS: Fine‐particle fraction (≤600 µm) yield was greater from flaxseed with 55 than with 105 g kg^?1 moisture content. Surface lipid content correlated positively with fine‐particle yield (r = 0.82, P = 0.01). At each moisture level, the surface lipid extracted from the fine‐particle fraction was greater with 9.5 than 0.475 kg min^?1 configuration of CCM and tended to be greater with the blunt than with the sharp hammer configuration of the hammer mill. CONCLUSION: Results indicated that flaxseed was more difficult to mill to a fine particle size at high than at low moisture content regardless of the mill configuration. Enhanced lipid oxidation was not detected in freshly milled flaxseed. Copyright © 2009 Society of Chemical Industry     

含水量影响冷冻饺子皮面团力学特性的研究

随着传统文化的升温,人们对非发酵冷冻面团的需求日益增加。研究在确定不同含水量的饺子皮坯冷冻和解冻条件的基础上,重点研究了含水量为46%、48%、50%、52%的面团在冷冻前和历经冷冻、冻藏及室温下自然解冻等工序处理后的硬度、内聚性、拉伸性等力学特性的变化。结果显示:质量为20g直径约为3.5cm的饺子皮坯的在-40℃的条件下,40min后可通过最大冰晶形成带;在-18℃的冻藏条件下,2h后温度基本稳定,室温下的适宜解冻时间为1h。在力学特性方面,含水量48%的面团拉伸性能最好,含水量46%的面团硬度最大,含水量50%的面团冷冻前内聚性最好,含水量为46%的面团冷冻后内聚性最好。     

水分含量对淡腌大黄鱼贮藏性的影响

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)。     

Effect of seed moisture content on the grinding kinetics,yield and quality of soybean oil

Grinding kinetics of soybeans at different moisture content (6%, 8% and 12%) were investigated. The hardness of soybean particles increased and showed brittle characters as the moisture content decreased. Three theoretical models for grinding, such as the Rittinger, Kick, and Bond model, were applied to characterize the grinding process of soybeans. The lower moisture content showed less grinding constants including Bond’s work index. Sigmoid model was successfully applied to describe the changes in particle size of soybeans at different moisture contents during grinding (r² > 0.96). The TBARS (thiobarbituric acid reactive substances) at different size of soybean flours were measured at 25 °C and 50 °C for 20 days and the yield of oil composition at different size of soybean flours were measured. As the particle sizes decreased, the TBARS values increased during storage, while the oil yield from soybean flours increased.     

Effect of moisture content on tensile properties of paper-based food packaging materials

Tensile properties (tensile strength and elongation at break) of 3 selected paper-based packaging materials, such as a vegetable parchment (VP) paper, a Kraft paper, and a solid-bleached-sulfate (SBS) paperboard, were determined with varying moisture contents. The monolayer moisture content of the paper samples determined using the Guggenheim-Anderson-de Boer (GAB) model were 3.45, 3.01, and 3.18 g water/100 g solids for the VP paper, the Kraft paper, and the SBS paperboard, respectively. Tensile strength and flexibility of paper samples was greatly influenced by the moisture content depending on the paper materials and paper manufacturing directions. However, the tensile properties of the paper samples maintained up to the monolayer moisture content, which corresponds to the water activity (Aw) of around 0.4 at 25°C.     

Effect of fungi and fungicides on the preservation of wheat seed stored with high and low moisture content

The protective effect of the fungicides captan, chloratalonil, pentachloronitrobenzene, thiram and the commercial mixture of captan and carboxin against storage fungi, as well as the possible toxic effect on seed viability, were studied on seed of the Salamanca wheat variety. The research was conducted with wheat seed stored at 25°C with a high and low moisture content: (a) seed stored at a high relative humidity of 85%, to allow the development of fungi and (b) seed stored under dry conditions, with seed moisture contents below 13%. The germination of wheat seed, either with high or low moisture content, was slightly inhibited by the fungicide carboxin immediately following seed treatment. It appears that the fungicide temporarily promoted a slight effect of seed dormancy; however, this effect disappeared during the storage period. The fungicides chloratalonil, captan and carboxin+captan prevented the activity of the storage fungi, and protected the germination of the wheat seed stored at 85% relative humidity.     

Effect of moisture content on mechanical properties of rice kernels under quasi-static compressive loading

Quasi-static compressive tests to determine the static mechanical properties of individual rice kernals were carried out on specimens tested uniaxially along the longitudinal axis. Apparent elastic modulus, failure stress, failure strain and energy density at failure were determined at five or six different moisture content levels ranging from 5% to 30% on dry basis (db). Compression speeds of 5 mm min⁻¹ and 10 mm min⁻¹ were used.Statistical analysis of the test results showed that moisture content had profound influence on the properties examined, especially in the range of 12% db to 18% db where quite drastic changes occur. An explanation in terms of bound water and free water in the kernel is given.     

Effect of temperature on the relationship between moisture content and dynamic rheological properties of Korean honey

Dynamic rheological properties of 27 Korean honeys with various moisture contents (16.2–20.1%) were evaluated at different temperatures (−5, 0, 5, 10, and 20°C) and were then correlated with moisture content. Dynamic moduli increased with a decrease in temperature while their predominant increases were noticed at −5°C. The relationships between moisture content and dynamic moduli seem to be influenced by temperature, and their correlations increased in the following order: −5>0>5 >10>20°C, showing greater determination coefficients (R²=0.942−0.966) at −5°C as compared to the other temperatures. In particular, the G″ at sub-zero temperatures had a better correlation (R²=0.965−0.966) than G′ (R²=0.899−0.942), indicating that the viscous property more closely correlated with moisture content as compared to the elastic property. This suggests that G″ determined at subzero temperatures can be useful for estimating the quality of honey.     

Effect of moisture content on selected physicochemical properties of two commercial hen egg white powders

After short-term storage at 23 °C, selected physicochemical properties of two hen egg white powders (with and without hydrolysis) were studied. Overall, the effect of moisture content on physicochemical properties of Hydrolysed Egg White powder (HEW) was more severe than those of Dried Egg White powder (DEW). The denaturation temperature (T_d) and its enthalpy change (ΔH_d) of ovalbumin in DEW followed an exponential model, as well as the T_d of HEW. The Gordon-Taylor equation modelled well the glass transition temperatures (T_g) of HEW and DEW. The Guggenheim-Anderson-de Boer (GAB) model fitted well to the type II moisture sorption isotherm. At the critical moisture content (12.0%, dry basis), compared with DEW, the colour of HEW began to darken dramatically and its hardness started to change significantly. These changes were closely related to the inherent characteristics of the two products. The mechanisms relevant to these physicochemical changes were discussed.     

Effect of water content and molecular weight on the moisture isotherms and glass transition properties of inulin

Inulin is being used more and more in foods due to its ability to add functionality either as a sweetener or fat replacer and also for its nutritional benefits. In this research, moisture sorption isotherms and glass transition temperature (T_g) as a function of moisture content and molecular weight for four inulins were determined. The T_g of the inulins was related to moisture content and also molecular weight. As with maltodextrins, the extent of lowering T_g was directly related to the average chain length (lower T_g with lower chain length). The sorption properties are also similar to maltodextrins, thus inulin may be useful in providing similar functionality as maltodextrins with almost no calories (1.5 kcal/g).     

织物含水率对其湿摩擦性的影响

织物的摩擦性能在一定程度上可以间接地反映其刺痒感和湿黏感。选用4种不同规格的聚酯/棉/麻混纺织物,利用FTT织物触感仪对织物进行动摩擦性能测试,通过调节织物含水率,模拟不同的湿度环境,研究织物在被汗液或雨水浸湿后表面动摩擦因数的变化。结果显示:织物含水率较小时,织物的动摩擦因数随着织物含水率的增加而呈现先增大后减小的趋势,织物刺痒感和湿黏感先增强后减弱;织物经、纬向摩擦性能由于织物密度不同而有所差异;当纱线中聚酯含量一定时,不同混纺比的聚酯/棉/麻织物摩擦性能的差异和规律并不明显。     

烘烤条件对压榨奇亚籽油中苯并[a]芘含量的影响北大核心CSCD

为探索不同烘烤条件下奇亚籽油中苯并[a]芘含量的变化规律,在不同的烘烤温度(60、100、140、180℃)和烘烤时间(10、30、50、70、90 min)下烘烤奇亚籽,采用液压压榨制备奇亚籽油。观察奇亚籽油色泽,并记录其气味。以MIL-101(Cr)为分散式固相萃取材料,采用分散式固相萃取-高效液相色谱-荧光检测器对苯并[a]芘进行定量检测。结果表明:烘烤条件对奇亚籽油的色泽、气味影响较大;随着烘烤温度的升高及烘烤时间的延长,奇亚籽油中苯并[a]芘含量逐渐升高,且烘烤温度越高、烘烤时间越长,苯并[a]芘含量增幅越大。参考GB 2762—2017及欧盟No 835/2011对食用油中苯并[a]芘的限量规定,并结合奇亚籽油的色泽、透明度和气味变化规律,在压榨前烘烤奇亚籽时,烘烤温度不应超过140℃,烘烤时间不应超过50 min。     

The effect of moisture content on the physico-mechanical properties of some hazelnut varieties

To better understand storage design requirements for hazelnuts, this research determined the physico-mechanical parameters (bulk density, true density, angle of internal friction, static coefficient of friction and dynamic coefficient of friction) of hazelnut varieties Tombul, Badem, Mincane, Çak?ldak and Sivri, for different structural surfaces. Physico-mechanical parameters (bulk density, true density, angle of internal friction, static coefficient of friction and dynamic coefficient of friction) were considered as the dependent variables, and moisture content (8%, 12%, 16%, 20%) as the independent variable. The temperature recorded in the laboratory during the experiments was 24.3 °C. The highest average value for bulk density (520 kg m⁻³) was recorded for the Sivri variety, the highest average value for angle of internal friction (35.4°) for the Badem variety, and the highest average value for true density (870 kg m⁻³) for the Mincane variety. The highest average values for static coefficient of friction (0.411) and the dynamic coefficient of friction (0.287) were recorded for concrete surfaces and the Badem variety.     

The influence of moisture content on the rheological properties of processed cheese spreads

Model processed cheese spreads were prepared from rennet casein, sunflower oil, water and a trisodium citrate/citric acid chelating salt system. The samples were cooked using a laboratory‐scale processed cheese cooker. The moisture content of the samples varied from 49.1 to 55.6%. The samples were characterized by dynamic rheology, rotational viscometry and fat particle size analysis. With increasing moisture content, the rheological behaviour of the samples changed from solid‐like (concentrated solution) to liquid‐like (dilute solution). The moduli decreased and the frequencies at which G′‐G′′ crossed over increased with increasing moisture content. Increasing moisture content resulted in an increase in pH and increase in the volume‐to‐surface diameter of the fat droplets. Rotational viscometry indicated that all the samples were shear thinning. The flow curves fitted a power law relationship (r² = 0.993). Thixotropic behaviour was displayed by all samples except those above 54% moisture. The shear stress at any particular shear rate increased with decreasing moisture content, indicating a stronger network structure in the low moisture samples.