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Puncture Test (puncture + test)
Selected AbstractsMEASUREMENT OF FIRMNESS OF FRESH-CUT SLICED TOMATO USING PUNCTURE TESTS , STUDIES ON SAMPLE SIZE, PROBE SIZE AND DIRECTION OF PUNCTUREJOURNAL OF TEXTURE STUDIES, Issue 5 2007MILZA M. LANA ABSTRACT In order to investigate the firmness of tomato slices, two experiments were performed. In the first one, Monte Carlo simulation was used to study the variation in firmness within and between slices. Adding more slices and more measurements per slice reduced the SD, but in general, the efficiency of adding more slices was higher. In the second experiment, the firmness of tomato slices was measured by puncture test during storage, using one of three flat-tipped cylindrical probes (3.5-, 2.5- and 1.5-mm diameter) in two directions, along or perpendicular to the main axis of the fruit. Changes in firmness were studied by nonlinear regression analysis. The same model could be applied to all combinations of probe size and direction with the same correction for shear and compression. It suggests that shear and compression forces decay with storage time according to the same mechanism, irrespective of the measurement direction. PRACTICAL APPLICATIONS Methodologies for both firmness evaluation and data analysis were presented. Monte Carlo simulation was used to optimize the number of samples for firmness assays. After calculating the experimental SD from preliminary experimental results, simulations were performed with different numbers of replicates and measurements per replicate, to find an optimal experimental design where the SD is minimized. Using nonlinear regression, the effects on firmness of probe size, puncture direction in relation to the plant tissue and storage time can be analyzed simultaneously. The incorporation of a correction factor to account for differences in firmness due to probe size was proposed. The relative influence of shear (s) and compression force (c) on the observed force is estimated. Results of interest for the industry were presented, confirming previous findings that the firmness of ripened tomato slices measured by puncture analysis does not change significantly during short-term storage at low temperature. [source] Microwave and convective dehydration of ethanol treated and frozen apple , physical properties and drying kineticsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2002Tomas Funebo The objective of this study was to examine how the drying kinetics and physical properties of apples are affected by pre-treatment with 95% ethanol or freezing at ,18 °C before microwave-assisted air dehydration at 50, 60 and 70 °C. Microwave heating was used to obtain these temperatures in the centre of the apple cubes. After dehydration the shrinkage and rehydration capacity were measured. The texture of dehydrated and rehydrated samples was analysed with a puncture test in a texture analyser. Samples were also analysed with confocal laser scanning microscopy to determine the correlation between physical and microstructural properties. Diffusivity in the different dehydration processes was calculated. Ethanol-treated apples showed both high rehydration and high effective rehydration capacity compared with the other samples. Freezing before dehydration increased the diffusivity and reduced the firmness of rehydrated apples compared with no pre-treatment. [source] MEASUREMENT OF FIRMNESS OF FRESH-CUT SLICED TOMATO USING PUNCTURE TESTS , STUDIES ON SAMPLE SIZE, PROBE SIZE AND DIRECTION OF PUNCTUREJOURNAL OF TEXTURE STUDIES, Issue 5 2007MILZA M. LANA ABSTRACT In order to investigate the firmness of tomato slices, two experiments were performed. In the first one, Monte Carlo simulation was used to study the variation in firmness within and between slices. Adding more slices and more measurements per slice reduced the SD, but in general, the efficiency of adding more slices was higher. In the second experiment, the firmness of tomato slices was measured by puncture test during storage, using one of three flat-tipped cylindrical probes (3.5-, 2.5- and 1.5-mm diameter) in two directions, along or perpendicular to the main axis of the fruit. Changes in firmness were studied by nonlinear regression analysis. The same model could be applied to all combinations of probe size and direction with the same correction for shear and compression. It suggests that shear and compression forces decay with storage time according to the same mechanism, irrespective of the measurement direction. PRACTICAL APPLICATIONS Methodologies for both firmness evaluation and data analysis were presented. Monte Carlo simulation was used to optimize the number of samples for firmness assays. After calculating the experimental SD from preliminary experimental results, simulations were performed with different numbers of replicates and measurements per replicate, to find an optimal experimental design where the SD is minimized. Using nonlinear regression, the effects on firmness of probe size, puncture direction in relation to the plant tissue and storage time can be analyzed simultaneously. The incorporation of a correction factor to account for differences in firmness due to probe size was proposed. The relative influence of shear (s) and compression force (c) on the observed force is estimated. Results of interest for the industry were presented, confirming previous findings that the firmness of ripened tomato slices measured by puncture analysis does not change significantly during short-term storage at low temperature. [source] Assessment of grape skin hardness by a puncture testJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 9 2008Hend Letaief Abstract BACKGROUND: The release of grape components during wine making might be related to the mechanical properties of the skin, in particular its hardness. Samples from three varieties collected during the 2005 vintage season in Piedmont, Italy, were tested for their skin hardness using a texture analyser. The goal was to understand the statistical interactions between three factors,variety, cluster position and puncture point,and their influence on the grape skin hardness. A discussion on the relationship between the size of the sample used and the confidence level is also provided. RESULTS: Results of the ANOVA test showed that there is an interaction between the variety and the puncture point when measuring the skin hardness with the break energy. The position of the berry on the cluster does not affect the berry skin break energy. We also show that a sample size depend on the variety tested. CONCLUSION: The break energy is more useful in understanding the effect of the three factors on the skin hardness. Other factors that might affect the puncture test applied to grapes need to be studied in the future and the usefulness of the test in winemaking will need to be further developed. Copyright © 2008 Society of Chemical Industry [source] PROBABILISTIC CHARACTERISTICS OF STRESS CHANGES DURING CEREAL SNACK PUNCTUREJOURNAL OF TEXTURE STUDIES, Issue 2 2007YOSHIKI TSUKAKOSHI ABSTRACT During puncture tests of Japanese cereal snacks, the force increases and decreases alternately. We herein compare the force,deformation curves recorded by two different testing machines and show that the number of changes in the curves depends on the testing machine. Thus, it is impossible to compare results obtained using different instruments. By removing the higher-frequency components of the force,deformation curves, small events are easily missed. The number of large events decreases when lower-frequency components are eliminated. This suggests the importance of providing the information on the frequency range of the testing machines. Nevertheless, the number of large force changes is similar between the examined machines. To model the size,frequency distribution, we selected a parametric probabilistic model from among the Weibull, exponential and Pareto distributions using Akaike information criterion and found that the Weibull or exponential distributions have a fit better than the Pareto distribution. PRACTICAL APPLICATIONS The methods developed in this work can be used to evaluate the quality of crisp snack food. By analyzing the samples obtained from a lot, samples with poor texture because of abnormal moisture levels and/or ingredients can be discerned and can be used to accept or reject the lot. 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