34 Figure 17. Resistant starch content of pea cake, rice cake, and rice cake prepared from ratio of rice
flour : sticky rice flour 90:10 at various cold setting conditions
4.4.2 Textural Properties
Influence of cold setting conditions to the textural properties of pea cake and rice cake were also investigated. The changes of textural properties involved hardness, adhesiveness, springiness,
cohesiveness, gumminess, and chewiness were summarized in Figure18. In this study, longer storage in refrigeration temperature significantly increased hardness,
adhesiveness, gumminess, and chewiness value of all samples. Hardness value of 267.94 g was obtained from pea cake after cold setting at room temperature for 6 hours. The same sample stored at
refrigeration temperature gave a higher hardness value of 521.71 g. Continued storage at refrigeration temperature for 24 hours leaded to the further increment of hardness value 851.16 g. Rice cake and
rice cake prepared from mixed sticky and rice flours 90:10 followed the same order of pea cake during cold setting. The increments of hardness values were 152.89 g, 197.78 g, 269.35 g, respectively
for rice cake, and 69.73 g, 78.63 g, 121.90 g, respectively for rice cake 90:10. The increment gel firmness is mainly caused by retrogradation of starch gels, which is associated with the syneresis of
water and crystallization of amylopectin, leading to harder gels Miles et al., 1985 in Sandhu and Singh, 2007. This was confirmed by the research work done by Ji et al. 2007 who studied the
staling of cake prepared from rice flour and sticky rice flour.
Adhesiveness also increased during cold setting. The increasing values for pea cake were - 48.76 g.s, -79.43 g.s, -96.68 g.s, respectively, whereas for rice cake and rice cake 90:10 were -53.85
g.s, -82.92 g.s, -100,30 g.s and -85.83 g.s, -90.09 g.s, -114.20 g.s, respectively. These results exhibited an opposite trend with that reported by Yu et al. 2009 in Yu et al. 2010, of which
amylose retrogradation contributed to the decreasing adhesiveness during storage.
35 Figure 18. Textural properties hardness, adhesiveness, springiness, cohesiveness, gumminess,
chewiness of pea cake, rice cake, and rice cake prepared from ratio of rice flour : sticky rice flour 90:10 at various cold setting conditions
36 The existing possible explanation is reported by Hoseney 1998. As the temperature goes
down, starch chains become less energetic, hydrogen bonds become stronger, giving a firmer gel. However, the starch chains have a tendency to interact strongly each other, thereby force the water out
of system. This resulted in moist surface of the cakes. Subsequently, the cakes became more adhesive.
As the gel got firmer, consequently, the energy required to masticate a solid food to a state ready for swallowing chewiness and the energy required to disintegrate a semi-solid food to a state
ready for swallowing gumminess were getting higher during cold setting and storage. Through cold setting conditions 6h, room temperature; 6h, 4
o
C; 24h, 4
o
C, gumminess gradually increased from 240.82, 483.82, to 744.52; 127.97, 178.06, to 250.85; and 60.40, 51.50, to 104.08, for pea cake, rice
cake, and rice cake 90:10, respectively. Chewiness increased as well as gumminess, ranged from 231.97, 464.40, to 713.77; 119.18, 163,70, to 232.64; and 49.78, 43.58, to 91.22, for pea cake, rice
cake, and rice cake 90:10, respectively.
In term of springiness and cohesiveness, there was no orderly trend through all samples after cold setting. The springiness values of pea cake 0.96 were same through all of cold setting
conditions. Rice cake behaved the similar trend with pea cake. Through cold setting conditions 6h, room temperature; 6h, 4
o
C; 24h, 4
o
C, there was no significant increment or decrement. There was an increment from 0.82 to 0.85, and finally 0.88 for rice cake 90:10. Summarized cohesiveness values
through all of cold setting conditions were 0.90, 0.93, 0.87 for pea cake; 0.84, 0.90, 0.93 for rice cake; and 0.87, 0.66, 0.85 for rice cake prepared from the mixture of rice flour and sticky rice flour at
the mixing ratio of 90:10.
Texture is a multi-parameter sensory attribute, and thus the changes in textural properties are definitely complex mechanism and even are not well understood. Therefore, further investigationss on
the textural properties and their influencing factors should be carried on He and Hoseney,1990 in Ji et al
., 2007.
4.4.3 Color Properties
