Thermal Analysis of the Freezing of Ice Cream Brickettes by the Finite Element Method

An unsteady-state theoretical analysis of the cooling of a large cross-section ice cream brickette is presented, to model the hardening process required for handling and storage purposes. The material physical properties, i.e. heat conductivity and thermal capacity, are considered temperature dependent, according to available experimental data on a vanilla ice cream. The material is assumed to be macroscopically homogeneous, in the sense that the phase change is simulated by adoption of effective physical properties. The bidimensional differential equations governing the process have been solved numerically using the finite element method, which is extremely powerful for defining optimal design criteria and process control strategies. Results are presented and discussed for different external heat transfer conditions.     

Optimization of process parameters in oriented strand board manufacturing with artificial neural network analysis

In the present work, an artificial neural network (ANN) model was developed for predicting the effects of some production factors such as adhesive ratio, press pressure and time, and wood density and moisture content on some physical properties of oriented strand board (OSB) such as moisture absorption, thickness swelling and thermal conductivity. The MATLAB Neural Network Toolbox was used for the training and optimization of the artificial neural network. The ANN model having the best prediction performance was determined by means of statistical and graphical comparisons. The results show that the prediction model is a useful, reliable and quite effective tool for predicting some physical properties of the OSB produced under different manufacturing conditions. Thus, this study has presented a novel and alternative approach to the literature to optimize process parameters in OSB manufacturing process.     

三维双正交小波包的性质刻划

研究三维双正交小波包的性质,推广了一元双正交小波包的概念,引入了三维不可分双正交小波包的定义并给出一种构造方法.使用分离变量法与时频分析方法讨论了三维不可分双正交小波包的性质,得到3个双正交性公式.由三维双正交小波包可以构造L2（R3）的R iesz基.     

The prediction of water activity of some supersaturated non-electrolyte aqueous binary solutions from ternary data

Binary data are required for prediction of the water activities of multicomponent aqueous solutions by various methods. At high concentrations, these methods would need binary data beyond the solubility limits of individual solutes. Such supersaturated data are usually lacking or very difficult to determine experimentally. The Zdanovskii–Stokes–Robinson equation, which has been shown to be a reliable and accurate method for predicting the water activity of complex solutions, may be applied in reverse to calculate the water activities of supersaturated binary solutions from ternary data. Hitherto unpublished supersaturated binary a _w data of mannitol, sucrose and urea obtained using this method as well as polynomials for their prediction are presented in this paper.     

INFLUENCE OF GEL NETWORKS IN CONTROLLING CONSISTENCY OF O/W EMULSIONS STABILISED BY MIXED EMULSIFIERS

A coherent explanation is presented of the mechanisms by which mixed emulsifiers of the surfactant/fatty alcohol type both stabilise and control the consistencies of oil-in-water emulsions. Original and published data are used to develop a theory in which the semisolid and other flow properties of emulsions are related to the nature, strength and extent of viscoelastic networks present in the continuous phases. These networks form from the interaction of surfactant solution with fatty alcohol and have similar properties to ternary system gels formed when the mixed emulsifiers disperse in water, in the absence of an oil. The theory is discussed with particular reference to liquid paraffin-in-water emulsions prepared with the surfactants anionic sodium dodecyl sulphate, cationic alkyltrimethylammonium bromides or non-ionic cetomacrogol and fatty alcohols cetyl and stearyl and their mixtures, especially cetostearyl. It may be used also to explain the properties of emulsions prepared with a variety of oils, surfactants and amphiphiles. The effects of variation in storage time, surfactant type (ionic or non-ionic), temperature, mixed emulsifier concentration, and alcohol and surfactant chain lengths on the rheological and microscopical properties of ternary systems and emulsions support this theory. The importance of small strain experiments (creep and oscillatory) in providing a true measure of consistency is emphasized. Continuous shear experiments, although theoretically less satisfactory, provide useful additional information when correlated with the small strain data.     

Rheological behavior of binary and ternary mixtures of polysaccharides in aqueous medium

The rheological behavior of mixtures of xanthan with different galactomannans is examined to evaluate the influence of the structure of galactomannan and that of the mixture composition on the physical properties; the larger synergy is observed for locust bean gum in the presence of xanthan. It is also shown that pH has only a slight influence on the rheology down to pH = 3.59; at lower pH, the G′ modulus decreases significantly.Then, the behavior of xanthan–methylcellulose mixtures is studied, paying particular attention to the storage modulus (G′) of the system, often equated to “gel strength”. The modulus values for direct dissolution of the two polysaccharides in 0.1 M NaCl show that xanthan and methylcellulose are incompatible. The rheological behavior observed is in agreement with DSC results which indicate that no specific interaction between the two polymers exists. However, upon increasing temperature, the modulus of methylcellulose increases substantially between 65 and 70 °C because of physical gelation and dominates the rheology of the mixtures. When temperature is decreased to 37 °C, the clear methylcellulose gel formed remains stable, still giving the main contribution to the overall rheology of the system. Finally, ternary systems are studied when xanthan is mixed with galactomannan and methylcellulose. In this case H-bonds involved in galactomannan–xanthan interaction break when temperature increases causing a decrease in rheological moduli which is then compensated by the gelation of methylcellulose giving an original large increase in moduli for the ternary systems. This can be interpreted as the presence of two independent but interpenetrating networks. The role of pH for these ternary systems is interesting: it is still dominated by methylcellulose and nearly independent of acidic pH (down to pH = 1.8).     

CHARACTERIZATION OF VISCOELASTIC PROPERTIES OF INDIVIDUAL RICE GRAIN BY MEASURING MECHANICAL IMPEDANCE

The viscoelastic properties of individual rice grains were measured by using a novel oscillatory squeezing instrument. Specifically, rice grains at different moisture contents and cooking durations were chosen as the model grain, and their viscoelastic characteristics, namely viscous modulus and elastic modulus, were determined. During the measurement, the grains were squeezed between a rigid bottom plate and a top round element oscillating at random frequencies in the range of 10–30,000 rad/s. The mechanical impedance of the rice samples, defined as the ratio between the force applied to the samples and the oscillation velocity, was obtained and used to calculate viscoelastic parameters. Measurements with the grains having moisture content between 12.8 and 29.1% indicated that both viscous and elastic moduli of the samples decreased significantly with increasing moisture content. The measured mechanical impedances of the samples showed that changes in viscoelastic properties for various cooking periods can be also monitored using the proposed oscillatory squeezing method.

PRACTICAL APPLICATIONS

In this study, a method for measuring viscoelastic properties of individual rice grain is presented. The technique is simple and easy to use. It can generate data for both elastic and viscous modulus properties for a single grain. There may be various practical applications for this instrument, such as textural characterization of grains having various chemical compositions and effect of cooking parameters on texture. The presented method can be also used to obtain textural differences between different varieties.     

Thermo-mechanical rice flour modification by planetary ball milling

Planetary ball milling is presented as an alternative way to improve the native flour properties by physical modification. A grinding protocol was developed by combination of grinding and pause stages. The effect of rotational speed (450–650 rpm) and milling time (10–20 min) on flour properties were determined using RSM method. The effect of milling conditions on flour attributes was significant. With increasing milling speed and time a significant increase in damaged starch, water-absorption and solubility indexes was observed. Changes in functional attributes, intrinsically related to structural and morphological properties of rice flour, were satisfactorily correlated with crystallinity loss, specific surface area and gelatinization degree. Modified rice flours presented pre-gelatinized characteristics which can offer new opportunities for flour applications, for example as ingredient for instant meal product. Flour modification can be controlled by selecting milling conditions. The distinctive characteristic of the planetary ball mill was the fast speed with which the modified flour was obtained which presented intermediate characteristics in relation with native and amorphous state.     

Elastic properties of extruded starchy melts containing wheat bran using on-line rheology and dynamic mechanical thermal analysis

Addition of wheat bran reduces the expansion volumes of extruded cereals. This may be explained by the influence wheat bran has on the elastic properties of the melt. The elastic properties of extruded refined wheat flour supplemented with wheat bran were investigated using a complementary on-line and an off-line rheological technique. The Bagley pressure (end pressure), reflecting extensional properties of the melt, was measured on-line using the orifice die method (dies with different lengths). The storage modulus of the extruded samples was measured using dynamic mechanical thermal analysis (DMTA). Increasing the bran concentration to an intermediate level significantly increased the Bagley pressure likely due to a reduced mobility of starch molecules. Further increasing the bran concentration significantly decreased the Bagley pressure. This might be caused by physical rupture of the melt at the die exit due to the low adhesion properties between starch and bran particles. This change in Bagley pressure indicates that the elastic properties of the composite melt may be reduced by bran particles. The storage modulus measured by DMTA was decreased when increasing the bran concentration, further supporting a potential decrease of the elastic properties of the melt with bran.     

无氯漂剂及其可应用性评价

综述了在化学浆漂白时可用来代替氯或二氧化氯进行漂白的各种无氯漂剂，并通过采用氯取代因子，二氧化氯取代因子，对其研究了解程度和工业化应用状况等各种参数，应用图表分类法对它们进行了分类，进而对它们在工业化生产中的可应用性进行了评价。     

Validation of HPLC method for quantitative determination of Tinosorb S and three other sunscreens in a high protection cosmetic product

A chromatographic method (high performance liquid chromatography) with a diode array detector was developed for simultaneous assay of Tinosorb S (bis-ethylhexyloxyphenol methoxyphenyl triazine) with three other sunscreen agents [benzophenone-3, butyl methoxydibenzoylmethane (avobenzone) and ethylhexyl methoxycinnamate] in high protection sunscreen. Separations were performed on a RP-18 Nucleodur Gravity column (150 x 4.6 mm, 5 mum) eluted with a ternary gradient mixture constituted of tetrahydrofuran, acetonitrile and an aqueous solution of acetic acid. The quantitative analysis was achieved with internal calibration performed with octyl dimethyl para-aminobenzoate (PABA) at 330 nm. In accordance with the analytical references (SFSTP, ICH, ISO...), the accuracy of the method was evaluated using a statistical approach of the validation parameters (specificity, response function, linearity, precision and trueness). For each studied ultraviolet filter, an accuracy profile was determined on a predicted range. These profiles show a graphical representation of the recovery percentage and confidence limits centred on 100%. The method is validated and can be used for analysis in cosmetic sunscreen products.     

酱油质量的简易检测法

合格酱油和配制的不合格酱油所含营养成分的种类和数量不同,其所形成的干固液滴的性状也不相同,本文根据这一不同点,介绍了一种酱油质量的简易检测法。该检测法的特点是对酱油样品通过肉眼直接观察鉴别酱油的优劣,并对该法的检测结果与常规的理化检验结果做了对比,说明本方法具有实用价值。     

Modified Jack-knife estimation of parameter uncertainty in bilinear modelling by partial least squares regression (PLSR)

A method for assessing the uncertainty of the individual bilinear model parameters from two-block regression modelling by multivariate partial least squares regression (PLSR) is presented. The method is based on the so-called “Jack-knife” resampling, comparing the perturbed model parameter estimates from cross-validation with the estimates from the full model. The conventional jack-knifing from ordinary least squares regression is modified in order to compensate for rotational ambiguities of bilinear modelling. The method is intended to make “do-it-yourself” multivariate data-analysis by non-statisticians more safe, in particular in cases with many collinear and noisy regressor and -regressand variables (which is very common in practice). Its use is illustrated by a real example, where the chemical and physical properties of different cocoa drinks are predicted from sensory analysis.     

小桐子油及其生物柴油多参数的物理特性预测及分析

运用相关物性数据估算方法,得到了小桐子油及其生物柴油的基本物性参数,有效地解决了临界参数难以测定的问题;同时估算出包括气体黏度、液体黏度、表面张力等与传递性质和平衡性质有关的物性参数;分别测定了不同温度下小桐子油及其生物柴油的相关物性,并与估算结果进行对比。结果表明:在实验温度下,小桐子生物柴油运动黏度的最大误差为5. 94%,表面张力的最大误差为5. 70%,估算结果较为准确。     

Evaluation of the compatibility between low pressure melamine (LPM) film printing substrates and inkjet inks

Surface coated wood-based panels play a major role in the forest products industry as materials for construction and furniture elements in numerous interior and exterior applications. Their most important feature besides appropriate mechanical performance and chemical durability is an appealing visual appearance. In this contribution, recent research on the compatibility between two UV-curable inks and different melamine formaldehyde based surface films is presented. The surface texture properties of the printing substrates were investigated by roughness measurements. Substrate surface free energy was measured by contact angle measurements using three different testing liquids covering a wide range of polarities (glycerol, ethylene glycol and diiodomethane). The physical shape of the inkjet ink drops which were placed on the LPM printing substrates was monitored and recorded over time and used as an indicator for the wetting behavior of the tested inks and hence the printability. By combining contact angle and pendant drop measurements the surface tension of the inks was determined. The theoretical findings were confirmed by technological printing tests. To this end, as a hands-on method to establish ink-substrate wetting and compatibility flow coating tests were run and the most suitable ink was selected for printing. The printing results were closely related to the surface properties of the printing substrates.     

麦麸纤维/小麦麸质蛋白复合膜碱性乙醇成膜体系影响因素研究

将小麦麸质蛋白(wheat gluten,WG)和麦麸纤维(wheat-bran cellulose,WC)通过溶液共混于碱性乙醇系统,采用流延成膜法制备复合膜。探讨成膜体系中料液比、麦麸纤维含量、甘油添加量、乙醇浓度、体系pH值及黄原胶添加量对复合膜物理性能抗拉强度(tensile strength,TS)、断裂伸长率(elongation at break,EAB)、水蒸气透过系数(water vapor permeability,WVP)、水溶性和透光性等的影响。结果表明:添加麦麸纤维能明显增强小麦麸质蛋白膜的抗拉强度,降低其水蒸气透过系数和水溶性,抗拉强度最高为20.44 MPa,比纯小麦麸质蛋白膜(TS=8.65 MPa)提高了140%;成膜体系各因素对复合膜各物理性能都存在不同程度的影响,其中甘油添加量影响最大,其次为麦麸纤维含量,黄原胶添加量影响最小。该研究可为进一步制备性能优异的小麦麸质蛋白复合膜提供技术参考。     

Modification of cassava starch by acetylation and pulsed electric field technology: Analysis of physical and functional properties

A dual pulsed electric field (PEF)-acetylation method to modify cassava starch was optimized. Also, the independent effect of each method on the functional properties of the starch was investigated. A PEF pre-treatment of 40 J/g (9.48 kV/cm) increased the acetylation degree by 47%. The dually modified starches presented the highest water solubility index (39.3%), a decrease of gelatinization enthalpy (5.4 J/g d.b.) and temperature (60.8 °C), and a better tolerance to refrigerated storage. A reduction of ordered structures was evidenced by FTIR. The PEF-modified starch also showed changes in its rheological profile, increments of the hydration properties and decreased retrogradation in comparison to the native sample, suggesting the potential of this physical method to modify starches. This work studied for the first time the effect of dual modifications by PEF and acetylation performed sequentially and not simultaneously. The results showed that the proposed scheme was efficient to improve the acetylation process.Industrial relevanceStarch is widely used in the food industry to modify texture, water retention and film making properties of products. Yet, because native starches rarely meet all the specific requirements for certain applications, physical and chemical modifications are applied to improve their functional properties. Acetylation is one of the most common chemical modifications for food uses. However, the pursue to minimize costs and environmental impact has motivated the search for complementary treatments to reduce the use of reagents and processing times. In the present study, a novel PEF-assisted acetylation process is proposed in which applying the physical and chemical treatments independently showed to be efficient to improve the acetylation process. This work scheme could enable the use of a common PEF system to assist different starch chemical modifications, offering a more versatile alternative for its industrial implementation.     

质构参数与花生物性测定的相关性

为明确花生在物性测定中与质构参数的相关性,本研究以两种表观差异较大的花生品种为样品,通过调控质构测定仪的关键参数进行研究。结果显示:不合适的质构测试参数能显著影响花生样品的物性特性结果并降低检测准确性。其中,压缩形变量对花生的硬度、弹性、内聚性、咀嚼性等物性特性造成显著影响,而压缩形变量为35%～50%之间时影响较小;测试速度与花生样品脆性成显著负相关性,拟定测试速度在40mm/min时脆性检测结果较为平稳;过高的剪切速率会严重影响剪切力结果的稳定性,造成系统误差扩大,控制剪切速率小于60mm/min能较好的稳定剪切力数据。不同种类花生之间物性测定结果不同,利用合适的测定参数就可以减小系统误差,进而更好的体现样品之间的物性差异。因此,花生样品在进行物性测定时,选择质构参数中压缩形变比在35%～50%范围,测试速度40 mm/min,剪切速率不高于60 mm/min对花生物性测定影响较小,这样的检测参数可以取得稳定数据。     

Gluten‐free bread: multiple time–intensity analysis,physical characterisation and acceptance test

The formulation of gluten‐free breads is challenging, once the gluten network is responsible for the physical and sensory properties of bread. This study presents a novel concept for making gluten‐free breads using sugar substitutes. The quality of gluten‐free breads was analysed by means of physical (specific volume and colour), textural (firmness, elasticity and chewiness) and sensory properties (time‐intensity analysis and acceptance test). Time‐intensity analysis showed that the sample developed with raw sugar had a higher intensity of sweetness, and the sample with stevia had a higher intensity of yeast flavour. The sample with frutooligosaccharides (FOS) presented a higher acceptance by consumers. Sample with stevia presented the higher intensity of yeast flavour (8.10) and the lesser mean of specific volume (2.83 cm³.g^?1); whereas sample with sugar who presented higher intensity of sweetness stimulus (5.20) also presented the higher mean of specific volume (3.80 cm³.g^?1). The addition of prebiotic and sweetener opens up new opportunities to develop gluten‐free breads that may present similar properties to those of wheat‐based breads.     

Determination of a thermal process schedule for guava (Psidium guajava Linn.)

A thermal process schedule for guava canned in syrup has been evolved on the basis of inactivation of pectinesterase (PE) which was found to be more heat resistant than peroxidase. The values for thermal inactivation and thermal resistance of PE in syrup homogenate containing guava pulp and sugar syrup in the ratio of 11:6 and total soluble solids content of 20% at pH 4.0 were     respectively. The F value of 1 was equivalent to 1.69 D . In commercial canning, a 2.5 D process is recommended which ensures a microbiologically safe and organoleptically acceptable product.
Process time was calculated both by graphical and formula methods. Calculation by the formula method using slopes of heating and cooling curves plotted on semilog paper by least squares analysis, and f _h/ U :g tables for actual values of j _c gave process times very close to those obtained by the graphical method. The process times required at different initial and processing temperatures are given.
To minimize viscosity increase in the covering syrup during storage, firming of guava in 1% calcium chloride solutions for 30 min prior to canning is suggested. In addition, use of covering syrup containing 0.125% ascorbic acid with or without citric acid (0.06%) yields a product of good colour, texture and flavour.