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Progress in Agricultural Engineering Sciences
Authors: Tamás Zsom, Viktória Zsom-Muha, Lien Phuong Le Nguyen, Dávid Nagy, Géza Hitka, Petra Polgári, and László Baranyai

gentle hit on the peppers’ tip – was analyzed by a Custom Fast Fourier Transform software called ‘Stiffness’. Acoustic stiffness coefficient (S) was calculated as S = f® * m * 10 −6 (N mm −1 ), where f is the characteristic resonance frequency in Hz of

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The objective of the work reported was to predict some sensory attributes of carrots stored under non-ideal conditions from the data obtained on taste measured by electronic tongue and on the physical properties (acoustic stiffness, cutting force, deformation work ratio and luminosity). There was a close correlation between the mechanical characteristics and the non-ideal storage time. Sensory evaluation showed significant ranking in “bite and chewing”, “sweet taste” and “global impression” attributes according to the Page test. Principal component analysis (PCA) plots were determined for the acoustic stiffness coefficient, cutting force and deformation work ratio and these showed that PC1 followed a tendency similar to that of the storage time. PCA plots were determined for the electronic tongue measurements and this PCA separated the sample groups along PC1 and PC2. We used partial least square (PLS) regression to predict “bite and chewing” from the acoustic stiffness coefficient, cutting force, and deformation work ratio with an acceptable correlation. The “sweet taste” was predicted from the electronic tongue measurement results with good correlation. The “global impression” was predicted by the acoustic stiffness coefficient, cutting force and deformation work ratio, and by the electronic tongue measurement results with close correlation.

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The acoustic response method is one of the most important dynamic methods used for assessment of the mechanical texture of different fruits and vegetables. The method is based on the mechanical excitation of the sample and the assessment of its resonant frequency. Different approaches are known for the interpretation of the vibration behavior of the samples having definite shapes. According to the most widely used interpretation, the stiffness of the sample ( s ) is dependent on the resonant frequency ( f ) and the mass ( m ) of the sample. The aim was to extend the acoustic response method to typically non-spherical samples (carrot, cucumber, etc.) to find a correct interpretation of the behavior of the sample and to introduce a stiffness coefficient suitable for characterization of the mechanical properties of a long shaped sample. According to Finite Element Modeling and experimental tests on carrot samples a close correlation was found between the resonant frequency and the effective length of the sample in a given shape range. A principally new stiffness coefficient was proposed for long shaped samples. It was found to be suitable for the characterization of the hardness of the vegetables in a wide size range.

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Progress in Agricultural Engineering Sciences
Authors: T. Zsom, V. Zsom-Muha, D. L. Dénes, L. Baranyai, and J. Felföldi

The aims of our research work were the investigation of postharvest changes of pear samples (Pyrus communis cv. Bosc kobak) during combined cold storage and shelf-life (storage at room temperature), the determination of quality changes by mainly non-destructive methods, the modeling of the changes of the non-destructive parameters (acoustic, impact stiffness coefficient, chlorophyll fluorescence parameters [F v/F m, F m/F 0 ]), and multivariate statistical analysis of the measured and predicted data based on the data of the non-destructive texture analysis (acoustic and impact methods), chlorophyll fluorescence analysis and laser scattering measurement. Storage Time Equivalent Value (STEV) was calculated and introduced based on mass-loss analysis. The changes of the non-destructive parameters were analyzed vs. this virtual storage time (STEV). The changes of acoustic, impact stiffness coefficient and chlorophyll fluorescence parameters can be predicted by exponential function. The predicted time constants of the parameters were 21.0, 45.8, 47.1, 83.4, acoustic, impact stiffness coefficient, F m/F 0, F v/F m, respectively. The lower the time constant, the quicker is the change of the given parameter during storage, the higher is its sensitivity. By this point of view, the percentage mass loss related sensitivity to the characterization of textural changes, the predicted acoustic stiffness coefficient was found to be more sensitive than the impact stiffness coefficient. The F m/F 0 value characterized more sensibly the changes of the chlorophyll fluorescence than in the literature commonly used F v/F m. The non-contact laser scattering method based significant PLS models were constructed to predict the quality related pear characteristics (mechanical properties, chlorophyll fluorescence parameters).

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