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研究概要

Effect of water activity on the mechanical properties of raw and blanched almonds by cutting test

研究機関名

Daegu University, Korea & University of California-Davis, U.S.A.

http://foodsys.daegu.ac.kr/leejun

代表者

Dr. Jun Ho Lee

本研究の主旨

Analysis of texture in almonds is a fast and accurate way to evaluate the quality of almonds; however, a suitable method to measure the textural quality of almonds needs to be found. Compression test is a very common method to obtain the textural properties of the dried products. However, the force–displacement curves can be irregular and irreproducible for the dried products with irregular geometry. In this study, the cutting test by a blade was used to measure the textural properties of almonds. The pre–dried almonds were stored into sealed plastic jars with a relative humidity range from 11.3% to 96.1% until almonds reached the equilibrium condition, and then textural properties of almonds were measured by using a TA.XT2 Texture Analyzer (Texture Technologies Corp., Scarsdale, NY⁄Stable Micro Systems, Haslemere, Surrey, UK) equipped with a load cell of 50 kg. The mechanical properties of almonds at different aw levels (0.11–0.96) and temperatures (25, 35, and 45℃) were measured by using a blade to cut the mid region of almonds perpendicularity to the full length of the almond. The effects of aw on the stiffness of raw and blanched almonds can be described by Fermi’s distribution model with R2 range from 0.934 to 0.974. The critical water activity ranges of almonds were in good agreement with the observed critical aw.

BDetermination of various mechanical parameters obtained from the cutting tests.

Fig.1 Determination of various mechanical parameters obtained from the cutting tests.


Representative force-time curves obtained from cutting test stored at 45?C: a) raw almonds, b) blanched almonds.

Fig.2 Representative force-time curves obtained from cutting test stored at 45℃: a) raw almonds, b) blanched almonds.

Representative force-time curves obtained from cutting test stored at 25 and 45?C: a) raw almonds, b) blanched almonds.

Fig.3 Representative force-time curves obtained from cutting test stored at 25 and 45℃: a) raw almonds, b) blanched almonds.


Effect of water activity (aw) on stiffness of almonds stored at different temperatures obtained from cutting test: a) raw almonds, b) blanched almonds.

Fig.4&Effect of water activity (αw) on stiffness of almonds stored at different temperatures obtained from cutting test: a) raw almonds, b) blanched almonds.

Mechanical parameters of raw almonds obtained from the cutting tests at 45?C.

Table.1 Mechanical parameters of raw almonds obtained from the cutting tests at 45℃.

Regression parameters of Eq. (4-4) as a function of aw applied to the stiffness of raw and blanched almonds obtained from cutting tests.

Table.2 Regression parameters of Eq. (4-4) as a function of aw applied to the stiffness of raw and blanched almonds obtained from cutting tests.