THE NUMBER OF ASSESSORS REQUIRED FOR NONPARAMETRIC TASTE DIFFERENCE TESTS1

The number of assessors required for nonparametric taste difference tests is a function of the degree of that difference which is considered to be of significance. This parameter is estimated nonparametrically as the plurality, i.e., the surplus proportion of assessors able to make the differentiation over the proportion attainable by chance. Tests of greater sensitivity require fewer assessors.     

A SMALL SAMPLE BACK EXTRUSION TEST FOR MEASURING TEXTURE OF COOKED-RICE

A small back extrusion test cell using about 12 g sample was used with an Instron Food Tester to measure the textural change of rice due to different degrees of cooking. The texture parameters determined with back extrusion test and the modified single-kernel technique appeared to be closely related. However, experimental measurements of extrusion energy and the extrusion point were found to be more sensitive and reproducible than the hardness measurements based on the modified single-kernel method. The extrusion point from the back extrusion test was shown to be the more sensitive index of cooked-rice texture for the cultivar tested.     

A COMPARISON OF SOME RAPID SCREENING TESTS FOR MALTING QUALITY

A series of rapid tests which have been proposed for the assessment of barley malting quality have been compared. The most accurate prediction of hot water extract was obtained by a multiple regression involving α-Amylase, Total Nitrogen and Grinding Resistance.     

EVALUATION OF PLASTICS PACKAGING MATERIALS FOR FOOD PACKAGING APPLICATIONS: FOOD SAFETY CONSIDERATIONS

In evaluating a packaging system for food packaging applications, consideration must be given to the physical properties, chemical composition and extractivity of the packaging material. The last point, extractivity, or migration from the packaging material to a food contact phase, is of major concern in the selection and use of plastics packaging materials for food packaging.
The present article deals specifically with migration of indirect food additives from plastics packaging materials and the scientific principles related to migrant transport or diffusion, as they apply to food safety. These principles and their experimental basis are discussed.     

MIXER VISCOMETER CONSTANT (k) FOR THE BROOKFIELD SMALL SAMPLE ADAPTER AND FLAG IMPELLER

The mixer viscometer constant (k¹) of a Brookfield viscometer equipped with a flag impeller and small sample adapter was determined using the slope and matching viscosity methods. Results showed that k' was equal to a constant value of 2.92 rad⁻¹ using the slope method and found to be a function of angular velocity (Ω), k'= 2.54(Ω)^−0.176, using the matching viscosity method. An example problem illustrating how the mixer viscometry principle can be used to determine the relationship between apparent viscosity and average shear rate is presented.     

FEASIBILITY OF ACCELERATED TESTS FOR BROWNING IN DEHYDRATED CABBAGE

SUMMARY– Feasibility of using accelerated tests for deterioration of dehydrated vegetables through nonenzymatic browning was evaluated. Studies were made on unsulfited freeze-dehydrated cabbage. Two procedures for shortening the time required to predict shelf life were used: (1) Extrapolation from high to low moisture contents; and (2) Extrapolation from high to low temperatures. A combination of the two procedures was also evaluated. It was determined that activation energy for browning was dependent on moisture content, and an equation expressing this dependence was developed. Equations relating rates of browning to moisture content at a given temperature were also obtained. Extrapolations based on either procedure, or on a combination of both, gave satisfactory results. The variance of the extrapolation-based estimates of browning rates was dependent on the number of points used for the extrapolation. The procedures used reduced the time required to obtain browning-rate data at low moisture contents from over a year to only 10 days.     

THEORETICAL CONSIDERATIONS ON DESIGN of MULTICOMPONENT TIME TEMPERATURE INTEGRATORS IN EVALUATION of THERMAL PROCESSES

Recently, the use of Time Temperature Integrators (TTIs) as an alternative means of process evaluation, besides in situ process monitoring and the physical-mathematical method, has received a lot of attention. the stringent requirement to which an adequate functioning TTI should respond, i.e. , the temperature dependence of reaction rate constants for the monitored target quality attribute and the TTI shall be identical, is hard to realize in practice. Therefore, multicomponent TTIs have been suggested to evaluate the integrated impact of time and temperature on a target quality attribute. These monitoring devices consist of a number of temperature sensitive units, each with its own response of reaction rates to temperature. the question how from the combined reading of these individual systems, the impact of the heating process on a target quality parameter can be predicted has not yet been answered.
In this theoretical study, we critically consider the restrictions of two interpolation methods in determining the impact on a target quality attribute from the reading of three other temperature sensitive systems. Possibilities of the 'Equivalent Point Method'and a polynomial expression as interpolation method are tested. Success of these transformations depends on kinetic characteristics of the components in the multicomponent TTI system and the actual product temperature history. Since only limited information is available on the product temperature     

A SYSTEM FOR RECORDING DEFORMATIONS IN TEXTURE TESTS*

An instrumental technique is described for recording food deformation in texture tests. The time required for the applied force to change between two levels is accurately recorded in digital form. Constant deformation rates are used so that deformation is directly proportional to time. The new readout is demonstrated with springs and selected foods to indicate its performance and show the inaccuracies that occur when using strip-chart recorders to measure deformations. The response of the new system is adequate to test products with a deformability up to 3400 g mm^-1 at deformation rates up to 100 cm min^-1 with less than 3 % error.     

STATISTICAL EVALUATION OF ARRHENIUS MODEL AND ITS APPLICABILITY IN PREDICTION OF FOOD QUALITY LOSSES

To minimize quality losses occurring during processing and storage and to predict shelf-life, quantitative kinetic models, expressing the functional relationship between composition and environmental factors on food quality, are required. The applicability of these models is based on the accuracy of the model and its parameters. In this paper, the calculation of the Arrhenius parameters and the accuracy of the derived model were compared, using three statistical methods, namely: linear least squares, nonlinear least squares and weighted nonlinear least squares. Results indicated that the traditional two-step linear method, was the least accurate and the derived energy of activation and the pre-exponential factor had the largest confidence interval. The latter was shown to have a profound effect on the precision of the calculated rate constant and the predicted shelf life. Based on previous reports that indexes of deterioration     

肉制品中多环芳烃前处理技术的研究进展

综述了索氏提取、超声波萃取、固相萃取、加速溶剂萃取等前处理技术，在肉制品中多环芳烃前处理技术中的应用进展，并对肉制品中多环芳烃前处理技术的发展趋势进行了展望。     

APPLICATION OF MULTIVARIATE STATISTICAL METHODS TO THE ANALYSIS OF THE COST, NUTRITIONAL AND SENSORIAL QUALITY FOR SOME PROTEINS USED IN FOOD FORMULATIONS

Incomplete proteins, of lower nutritional value, are usually more available and less expensive than complete high quality proteins. In the development or reformulation offood products, sensory,“nutritional‐quantitative” and economic aspects may be superimposed on the “nutritional‐qualitative” aspects, to the detriment of consumers. In the present study, three protein ingredients were mixed at different proportions and their nutritional and sensory properties were evaluated by a multivariate approach, using principal component analysis (PCA) in order to identify the type of association between these properties and cost. A strong positive correlation was observed between nutritional quality and cost of the mixtures, with a correlation coefficient of the order of 0.82, while the vector concerning the sensory quality was practically orthogonal to the nutritional vector, suggesting a low correlation between these two features. Thus, we recommend that the protein quality be evaluated, classified and, if possible, expressed on the label especially in foods destined to institutional programs of children's foods, hospital diets and foods used as meal substitutes.