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
Color measurements serve as quality index of raw and processed food for use in quality control, determination of conformity of food quality into a claimed specification, and analysis of
quality change as a result of food processing and storage Socaciu and Diehl, 2009. Color properties involved L, a, b values of pea cake, rice cake, and rice cake prepared from mixed flour were
investigated through three condition of cold settings 6h, room temperature; 6h, 4
o
C; 24h, 4
o
C. The lightness of pea cake was found to slightly increase 64.41 to 65.53 after storage the
refrigeration temperature for 6 hours Figure 19. Longer storage at refrigeration temperature 24h, 4
o
C gave a significant lower L value 61.22. The same trend was exhibited by rice cake. The increment of L was from 57.42 to 58.83, and longer storage resulted in lower value 57.27. On the
other hand, rice cake prepared from mixing ratio of 90:10 between rice flour and sticky rice flour behaved differently. There was a linear increment through cold setting conditions 56.11, 56.61,
56.66.
In term of greenness or redness ± a value, pea cake behaved the same trend in which there was an increment from -1.33 to -1.38, then decreased to -1.09 Figure 20. Inversely, both rice cake
and rice cake 90:10 behaved disorderly compared to that of pea cake. The a value of them through cold setting conditions were -2.98, -3.31, -3.31; and -3.04, -3.20, -3.11, respectively.
The yellowness b value of pea cake increased from 13.57 to 15.05 after storage at 4
o
C for 6 hours, however the value then decreased to 10.27 Figure 21. The similar order increased then
decreased was also exhibited by rice cake. The value raised from 2.68 to 4.25 then decreased to 3.92.
37 Rice cake 90:10 possessed its own order through cold setting conditions. Linear increment in b
value was exhibited 2.24, 3.50, 3.63.
Figure 19. L value of pea cake, rice cake, and rice cake prepared from ratio of rice flour : sticky rice flour 90:10 at various cold setting conditions
Figure 20. a value of pea cake, rice cake, and rice cake prepared from ratio of rice flour : sticky rice flour 90:10 at various cold setting conditions
Figure 21. b value of pea cake, rice cake, and rice cake prepared from ratio of rice flour : sticky rice flour 90:10 at various cold setting conditions
38 The most possible explanation on color properties in starch-based product was that the changes
were mainly due to the retrogradation of amylose molecules. Longer storage gave more interaction between starch chains, and eventually the formation of crystals. As a result, gel became opaque, more
rigid and rubbery Hoseney, 1998. This established the reports that at the early stage of retrogradation process, turbidity development was occurred Karim et al., 2000. Furthermore, Sandhu and Singh
2007 reported that turbidity values of starch suspensions increased progressively during storage of starch gels at 4
o
C. Turbidity development in starches during storage has been attributed to the interaction of several factors, such as granule swelling, granule remnants, leached amylose and
amylopectin, amylose and amylopectin chain length, intra or interbonding, lipid and cross-linking substitution Jacobson et al., 1997 in Sandhu and Singh, 2007.
Relationship between color and other properties was reported to be a complex thing. The key problem that prevents accurate and reproducible color measurements is that most foods have non-
uniform surfaces and heterogenic composition, with profound effects on light and color reflection and perception Socaciu and Diehl, 2009. In addition, study on color properties of starch-based product
and its influencing factors have been received little emphasis, and thus further study is highly required.
40
V. CONCLUSIONS AND RECOMMENDATIONS
5.1 CONCLUSIONS
First experiment was aimed to investigate the effects of flour type pea flour, rice flour, mixture of rice flour and sticky rice flour at the ratio of 100:0. 97.5:2.5, 95:5, 92.5:7.5, 90:10 to the
physicochemical properties of resulted cakes. Pea flour, rice flour, and sticky rice flour were different in the granular morphology and chemical composition involved moisture, ash, protein, crude fat, and
amylose content, consequently different in the thermal and pasting properties. Mixing rice flour and sticky rice flour in such ratios markedly affected the apparent amylose content. Through ratios of rice
flour and sticky rice flour, the higher sticky rice added, the lower the amylose content in the mixtures.
Pea cake, rice cake, and rice cake prepared from mixed rice flours showed significant difference in term of starch digestibility, textural and color properties. Pea cake possessed the highest
amount of resistant starch. Through ratios or rice flour and sticky rice flour, increment of sticky rice portion lowered the resistant starch amount in the cakes. In term of main textural properties, highest
value of hardness was obtained from pea cake, whereas highest value of adhesiveness was obtained from rice cake with the extreme addition of sticky rice flour ratio of 90:10. As the portion of sticky
rice flour increased in the cake, the hardness decreased, and conversely the adhesiveness increased. Pea cake and rice cake was significantly different in the color properties L, a, b values, however
increasing addition of sticky rice flour to the rice flour in the cakes did not follow certain trend.
In the second experiment, effect of cold setting conditions 6h, room temperature; 6h, 4
o
C; 24h, 4
o
C to the starch digestibility, textural and color properties of pea cake, rice cake, and rice cake ratio of 90:10 were investigated. Results showed that longer storage at refrigeration temperature increased
resistant starch amount in the rice cake and rice cake ratio of 90:10, but not in pea cake. Both hardness and adhesiveness increased during cold setting for all samples. There was no certain trend of
color properties through cold setting conditions, however it seemed, especially in pea cake, that L, a
, b values tended to decrease at longer storage due to retrogradation. Changes in the physicochemical properties and starch digestibility were mainly influenced by apparent amylose
content.
5.2 RECOMENDATIONS
Study on physicochemical properties and starch digestibility of starches are extremely numerous. However, little emphasis has been given to the specific-indigenous food product. Hence,
such research should be carried out more intensive. Sensory evaluation should also be held considering the consumer acceptance. In addition, literatures stated that some relationships among
starch properties remain unclear and are not well understood, thus further investigation on starch properties should be conducted more deeply.
