大豆分离蛋白膜阻湿性优化及其在微波食品中的应用

本研究通过添加葡萄糖或亚硫酸钠、采用超高压均质及超高压均质联合葡萄糖改性的方法以提高大豆分离蛋白膜的阻湿性。结果表明其膜阻湿性关系为:超高压均质联合葡萄糖改性超高压均质(100MPa)改性添加葡萄糖(0. 1%)改性添加亚硫酸钠(0. 1%)改性。扫描电镜结果表明,经4种改性方法处理后的大豆分离蛋白膜疏松的网状结构变得致密,且其中经超高压均质联合葡萄糖改性后膜的结构最为致密。利用此复合改性大豆分离蛋白对鸡米花进行涂膜处理后,可有效减少水分向外壳的扩散,复热后鸡米花口感更加酥脆。     

Moisture Dependent Physical Properties of Dry Sweet Corn Kernels

Physical properties of sweet corn kernels have been evaluated as a function of kernel moisture content, varying from 9.12 to 17.06% (db). In the moisture range, kernel length, width, thickness, and geometric mean diameter increased linearly from 9.87 to11.09 mm, 7.41 to 9.25 mm, 3.25 to 4.37 mm, and 6.18 to 7.62 mm, respectively, with increase in moisture content from 9.12–17.06%. The sphericity index, kernel volume, kernel surface area, and thousand seed weight increased linearly from 62.6 to 68.8, 93.8 to 194.3 mm³, 120.1 to 182.9 mm², and 220 to 268 gr, respectively. Apparent density and bulk density decreased linearly from 1.315 to 1.232 g/cm³ and 0.765 to 0.698 g/cm³, respectively, while bulk porosity increased from 41.8 to 43.3%. The highest static coefficient of friction was found on the plywood surface. The static coefficient of friction increased from 0.680 to 0.891, 0.605 to 0.741, and 0.530 to 0.644 for plywood, galvanized iron, and aluminum surfaces, respectively. The angle of repose increased linearly from 30.2 to 35.2° with the increase of moisture content.     

Gel Properties of Surimi from Various Fish Species as Affected by Moisture Content

Torsion, punch, and color tests as affected by moisture content were evaluated for surimi from pollock, Pacific herring, arrowtooth flounder, and Pacific whiting. Torsion stress and strain decreased linearly with increased moisture content but strain values were less sensitive to moisture than were stress values. This finding enabled mathematical normalization of torsion stress and strain values rather than adjusting the moisture content of samples prior to testing. Punch test results, while linearly related to moisture content, were not as consistent as torsion test results. The L* and whiteness increased with higher moisture content, but changes in a* and b* values were not consistent for surimi from different species.     

Moisture Dependent Geometric and Mechanical Properties of Wild Pistachio (Pistacia vera L.) Nut and Kernel

In this research, wild pistachio (Pistacia vera L.) nuts and kernels were analyzed for selected geometric properties and mechanical behavior under compression loading. The average length, width and thickness arithmetic and geometric mean diameter of wild pistachio nuts at 5.83% w.b. were 13.98, 8.76, 7.25, 9.93, and 9.75 mm, while the corresponding values of kernels at 6.03% w.b. moisture content were 11.07, 5.92, 4.83, 7.21, and 6.88 mm, respectively. As the moisture content of pistachio nut increased from 5.83 to 30.73% w.b., the bulk density, apparent density and terminal velocity were found to increase from 521 to 543 kgm^?3, 809 to 829 kgm^?3, and 5.51 to 6.29 ms^?1, respectively, whereas porosity decreased from 35.14% to 34.63%. The results revealed that wild pistachio nut required higher rupture force and energy to crack wild pistachio nuts for compression along the L-axis as compared to other two axes.     

Thermal Properties of Ration Components as Affected by Moisture Content and Water Activity During Freezing

ABSTRACT: Beef roast with vegetables is an example of a meal, ready‐to‐eat (MRE) ration entrée. It is a mixture of meat, potato, mushroom, and carrot with a gravy sauce. The thermal properties of each component were characterized in terms of freezing point, latent heat, freezable and unfreezable water contents, and enthalpy during freezing using differential scanning calorimetry. Freezing and thawing curves and the effect of freezing and thawing cycles on thermal properties were also evaluated. The freezing points of beef, potato, mushroom, and sauce were all in the range of −5.1 to −5.6 °C, but moisture content, water activity, latent heat, freezable and unfreezable water contents, and enthalpy varied among these components. Freezing temperature greatly affected the unfrozen water fraction. The unfreezable water content (unfrozen water fraction at −50 °C) of ration components was in the range of 8.2% to 9.7%. The freezing and thawing curves of vegetables with sauce differed from those of beef but took similar time to freeze or thaw. Freezing and thawing cycles did not greatly affect the thermal properties of each component. Freezing point and latent heat were reduced by decreasing moisture content and water activity of each component. Water activity was proportionally linear to freezing point at a_w > 0.88, and moisture content was proportionally linear to freezable water content in all ration components. Water was not available for freezing when moisture content was reduced to 28.8% or less. This study indicates that moisture content and water activity are critical factors affecting thermal behavior of ration components during freezing.     

Dough Properties and Crumb Strength of White Pan Bread as Affected by Microbial Transglutaminase

Microbial transglutaminase forms nondisulfide covalent crosslinks in proteins and is being used in foods. This enzyme may produce beneficial effects during breadmaking that are comparable to traditional oxidizing improvers, hypothesized to act via formation of disulfide crosslinks. Transglutaminase greatly improved the crumb strength of baked loaves and provides a potential solution to a common consumer complaint. Transglutaminase also reduced the required work input and substantially improved the water absorption of the dough. Each of these effects would lower processing costs for commercial baking     

Extrusion of Soybean and Wheat Flour as Affected by Moisture Content

The effect of moisture content (MC) on texture and properties of extrudates with varied ratios of soybean flour (SF) and wheat flour (WF) was studied. A single-screw extruder was used at screw speed 200 rpm. MCs of blends were 16, 17 or 18%, w.b. The properties of extrudates depended on flow rate of the material during extrusion. The flow rate revealed a nonlinear dependence on the blend composition and the MC at the same volume of filling of the screw feeding section. The expansion ratio of WF or SF extrudates increased with lowering of the MC. Unexpectedly, the expansion ratio decreased with lower MC for the composite extrudates. Optimal extrudate properties at 16% (w.b.) MC corresponded to 80, 90 or 100% (d.b.) WF and 20, 10% or no SF, respectively. At 17 and 18% MC, optimal properties were found for products containing 80 or 90% WF and 20 or 10% SF, respectively.     

Pecan Kernel Breakage and Oil Extracted by Supercritical CO2 as Affected by Moisture Content

During supercritical CO₂ extraction of oil from pecans, kernel breakage frequently occurs when the depressurization time is short. The purpose of this study was to investigate the effects of initial moisture content of pecan kernels and moisture equilibration time on pecan breakage and oil recovery when extracting with supercritical CO₂. Initial pecan moisture content, adjusted to 3.5% to 11.0%, had a significant effect on breakage when using a short depressurization time. With higher pecan moisture, less kernel breakage occurred. Increasing moisture equilibration time from 1 to 48 h reduced kernel breakage and produced an average of 30% more oil during extraction. Moisture content did not significantly affect the amount of oil extracted.     

Surimi Gel Colors as Affected by Moisture Content and Physical Conditions

Colors (CIE L*, a*, and b*) of Alaska pollock (7′heragra chalcogramma) and Pacific whiting (Mecs productus) surimi gels were evaluated and related to compositional and physical conditions during preparation and measurements. Ten samples were used in each treatment. Water addition, sample size, species, cooking and test temperatures, and freeze/thaw affected lightness (L*) and yellowness (b*) values, while outside light conditions at measurement did not affect colors. Greenness (-a*) values were less affected by all conditions.     

Moisture Retention and Textural Properties of Ground Chicken Meat as Affected by Sodium Tripolyphosphate, Ionic Strength and pH

Batches of ground chicken meat were mixed with 10% solutions containing 0.0–5.0% sodium tripolyphosphate and sufficient NaCl to adjust the ionic strength (IS) of the solutions from <0.7 to 6.0 at pH 6.5 to 9.5 in a 6 × 4 × 7 factorial experimental design. Patties prepared from the mixtures were evaluated for pH, cooking loss, and objective texture characteristics. Most effects of STPP were attributable to the direct effect of STPP on IS. However the ability of the phosphate to alter textural properties was greater at a pH value near the pK_a of the phosphate.     

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.     

Influence of Variety,Moisture Content,Kernel Size and Applied Current Frequency on the Electric Properties of Wheat Grain

The work aimed at determination of electric properties of wheat grain in dependence on its variety, moisture, geometrical features of kernels and applied current frequency. Wheat grain of 4 Polish winter varieties: Korweta, Juma, Mikon and Kobra from harvest 2001 were used as the material for study. Grain was sized into 3 fractions: (1) > 2,8mm, (2) 2,5–2,8mm, and (3) 2,2–2,5mm. Basic geometrical features were determined for not sorted grain (control sample) and its three fractions by the use of digital image analysis. Electric properties of grain (at 11% and 15% moisture content) have been performed with the Hewlett Packard 4263B meter. Measurements of impedance, resistance, admittance, conductance, as well as equivalent parallel capacitance and equivalent series capacitance were made. Obtained results were subjected to statistical analysis with the use of Statistica? programme. Changes in electric properties of grain significantly depended on all of studied factors. Most of all significant correlations appeared between geometrical features and studied electric properties of grain of 15% moisture. Statistical analysis of the results proved significant linear correlations between electric properties of kernels and their length, perimeter and circularity coefficient R_C2 at higher measurement frequencies.     

花生壳/仁的吸附等温线与热力学特性

为了解花生壳与花生仁的含水率、水分活度(a_w)与温度的关系,提高花生的贮藏稳定性。研究花生壳与花生仁在10、20、30℃时的吸附等温线;探讨花生壳与花生仁的净等量吸附热(q_(st))、微分熵(S_d)、扩张压力、积分熵、积分焓、熵-焓互补、玻璃化转变温度(T_g)等热力学特性。结果表明,花生壳与花生仁的水分吸附呈Ⅲ型等温线。温度一定时,花生壳与花生仁的干基含水率随a_w增加而增加。描述花生壳与花生仁吸附特性的最适模型为GAB模型。花生壳与花生仁的q_(st)与S_d均随含水率增加而降低。扩张压力随a_w增加而升高,但随温度升高而降低。积分焓随含水率增加而降低,而积分熵随含水率增加而升高。花生壳的q_(st)和S_d均高于花生仁,而同一温度条件下花生仁的扩张压力高于花生壳。含水率相同时,花生仁积分焓低于花生壳,而花生仁的积分熵则高于花生壳。花生壳与花生仁水分吸附过程均为焓驱动、自发过程。花生壳与花生仁的T_g随含水率增加而降低,相同含水率时,花生壳的T_g值高于花生仁。根据状态图得到温度为10℃时,花生壳与花生仁的临界水分活度与临界含水率分别为0.80、0.175 4 g/g与0.68、0.095 5 g/g。研究结果可为花生干制工艺及其干制品贮藏稳定性提供理论依据。     

Selected Geometric Characteristics,Density, and Mechanical Properties of Unsplit Pistachio Nut

In this study, several physical properties of unsplit pistachio nut were determined as functions of moisture content. By increasing moisture content from 5 to 20% all geometric characteristics increased linearly. Also, apparent and bulk density increased from 803 to 872 kg/m3 and from 458 to 575 kg/m3, respectively, while porosity decreased from 43% to 34%. Coefficient of static friction of the sample nuts on galvanized iron, plywood, and rubber surfaces increased linearly with moisture content. Nut splitting force decreased from 142 to 21 N and energy increased from 20 to 52 mJ with increasing moisture content from 5 to 20%.     

Physical Properties of Cooked Wheat Grains as Affected by Cooking Temperature and Duration

The physical properties of soft and hard wheat grains, cooked with steam under pressure, were investigated. These included water uptake, rheological properties as observed by modulus of elasticity (E) and maximum compressive contact stress (S_max), color in CIE L*a*b* system and pasting properties by Rapid Visco Analyzer (RVA). Four cooking temperatures (110, 120, 130 and 1408 C) and six cooking durations (20, 40, 60, 80, 100 and 120 min) for each temperature were studied. Water uptake (WU) and rheological properties were analyzed immediately after cooking conditions were achieved. For color and pasting properties, cooked wheat grains were dried at low temperature and ground before analysis. It was found that WU increased proportionally with cooking temperatures and durations. Hard wheat grains tended to absorb more water than soft wheat grains. Both E and S_max decreased rapidly when wheat grains were cooked. Such decreases were found to be more rapid in hard wheat grains. Wheat grains became darker when cooked, resulting in the decrease of L* values and increase of a* and b* values. Cooked wheat grains lost their natural pasting properties compared to uncooked grains, resulting in the decrease of viscosity in their RVA profiles. The experimental data fitted well in second-order polynomial models (p # 0.0001). The built models were sufficiently accurate for most of the studied properties (R² ranging from 0.58–0.97).     

Thermal Properties of Kerstingiella geocarpa Seeds as Influenced by Moisture Content

The specific heat capacity, thermal conductivity and thermal diffusivity of Kerstingiella geocarpa seeds were determined as a function of moisture content. The initial moisture content of the seeds determined using the ASAE standard test was 10.0 % (d.b). The specific heat capacity of Kerstingiella geocarpa seed increased from 155.83 to 204.45 Jkg^?1k?1, as the moisture content increased from 10 to 30 % (d.b). The thermal conductivity of the seed increased from 5.13 × 10^?2 to 4.87 × 10^?1 Wm^?1k^?1, as the moisture content increased. The thermal diffusivity of the seed increased from 2.35 × 10^?4 to 3.66 × 10^?3 m²s^?1, as the moisture content increased. These values indicate the ability of the Kerstingiella geocarpa seed to retain heat when processed. The regression models that could be used to adequately express the relationships existing between the thermal properties of the Kerstingiella geocarpa seed and moisture content were established.     

Rheological Properties Including Tensile Fracture Stress of Semolina Extrudates Influenced by Moisture Content

Semolina extrudates were reshaped, immediately after extrusion to form 0.5 mm thick × 2 mm wide × 130 mm long strips. Moisture content (W) was adjusted to 5 to 39% (dry basis) equilibrating in desiccators containing saturated salt solutions. The following tensile rheological properties of the prepared samples were determined at room temperature (21-24°C) using a Rheometrics solid analyzer: Young modulus (E), yield stress (σ_y), fracture stress (σ_c) and fracture stain (?_c). Each of E, σ_y and σ_c was fitted by a semilogorithmically linear function of W with a negative slope. The property ?_c fitted two semilogarithmically linear functions: for W < 24.2% a line with a positive slope and for W > 24.2% a line with near zero slope. Such data for moisture ranges used in conventional pasta drying can help to optimize conditions for pasta production without stress cracking.     

The Effect of Seed Size and Microstructure on Their Mechanical Properties and Frictional Behavior

The seeds of grass pea were selected based on their size, hardness, and microstructure in order to examine their mechanical properties and friction coefficients versus mass. The size, shape, mass, and static friction coefficients of seeds were determined using adequate methods. Seed hardness was measured using compression methods, and it was described by typical and corrected fracture parameters. The microstructure of cotyledons and seed surfaces was viewed using scanning electron microscopy, and surface microimages were processed by digital image analysis. The length of the examined seeds ranged from 5.86 mm to 14.25 mm, their width ranged from 5.47 mm to 12.93 mm, thickness from 4.59 mm to 6.21 mm, mass from 0.110 g to 0.570 g, projected area from 28.55 mm² to 148.73 mm², and roundness from 1.060 to 1.126. The static friction coefficients for seeds of the examined accessions and varieties determined on steel, wood, rubber, and PVC surfaces were 23.4–33.3°, 24.4–37.2°, 29.6–50.4°, and 22.4–35.4°, respectively. For grass pea seeds of irregular size and shape, corrected fracture energy values (with regard to seed mass and volume) were proposed as a more robust parameter of seed hardness. The values of the static friction coefficient depend on both seed mass and the microstructural properties of seed surface digitalized with the involvement of image analysis techniques.     

Physicochemical Properties of Sweet Potato Flour and Starch as Affected by Blanching and Processing

The effects of blanching on physicochemical properties of flours and starches prepared from two varieties of sweet potatoes (Mun‐Kai and Negro) were studied and compared. The pasting temperature and peak viscosity of starches, respectively, were 74 and 80 °C and 381 and 433 RVU. The pasting temperature (74.0‐94.8 °C) of flours was greater than that of starch, depending on the variety and blanching process. However, the peak viscosity (ca. 103‐120 RVU) of flours was lower than that of the corresponding starches. Partial gelatinization of starch granules was observed as a result of a 1‐min blanching. Composition of starch and flour was found to affect swelling power and solubility. The starch content of starches, flours from unblanched sweet potato and flours from 1‐min blanched sweet potatoes were 97; 66.3 and 74.9; as well as 36.6 and 40.4%, respectively. Amylose content of flours and starches varied from 17.2‐20.8%.