Texture and color of potato products

University dissertation from Department of Food Engineering, Lund University

Abstract: Texture and color are the most important parameters in the definition of the quality of potato products, but usually their subjective measurements do not give any reproducible results due to the complicating factors related to human perception. In order to understand the factors that can affect the texture and the color of the potato products during processing, instrumental techniques have been developed for quantifying those parameters. A punch test with 3-point support was developed for texture analysis of potato chips. This simple modification was used as an improved procedure to analyze the texture of potato chips giving less variation in the analytical results. In this technique, the chips were placed on a support with 3-points, and punched in the middle with a rigid punch. Maximum breaking force (fracture force) and deformation were the texture parameters evaluated. For color analysis, a new easy and inexpensive procedure was developed. This color technique quantifies the color of potato chips (or other products) by using computerized video image analysis. This procedure offers some advantages over the conventional colorimeter including no sample pretreatment, rapid generation of reproducible results, and the possibility of quantifying color in homogeneity and other characteristics of the potato chip surface. The results obtained can be expressed as CIE defined L'a'b' colors from images. Both instrumental analyses for texture and color measurements of potato chips were correlated with their sensory evaluations. The results obtained indicated that these instrumental techniques could be used to estimate the sensory attributes of potato chips which offers the possibility to predict the quality of chips during processing. A new in situ technique was also developed to study the effect of heat treatment on potato texture. This technique involved the use of an oscillatory test and the force required to bend the sample to a constant deformation was recording during heating. This procedure allowed a well-defined and quantifiable measurement of potato stiffness during heat treatment.

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