Identification of a mixture in a Thai aromatic rice (Khao Dawk Mali 105) | |
| Author | Jiraporn Sripinyowanich |
| Call Number | AIT Thesis no.FB-06-17 |
| Subject(s) | Rice--Processing--Thailand Rice--Thailand Khao Dawk Mali 105 |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Food Engineering and Bioprocess Technology, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. FB-06-17 |
| Abstract | Physical characteristics (size, shape, and whiteness), physicochemical properties (amylose content, gel consistency, alkali spreading value, and dye-stained rice grain), changes during soaking (size expansion and water absorption), cooking qualities (cooking time, size and volume expansion during cooking, water absorption during cooking, and residual solids in cooking water), eating qualities (cooked rice texture and rice aroma), functional properties (pasting properties, freeze-thaw stability, and cooked rice retrogradation), and DNA were determined to differentiate among four varieties of Thai rice consisting of three aromatic (Khao Dawk Mali 105; KDML105, cultivated in Northeast region of Thailand, Khao Hom Changwad; HCW, KDML105 cultivated in Central region of Thailand, and Pathum Thani 1; PTT1, new breeding aromatic rice) and one non-aromatic (Chainat 1; CNTI, having the same appearance as KDML105) rice. Difference between KDML105 and HCW (having 93% of authentic KDML105 evaluated by DNA based cultivar identification method) was determined to investigate the influence of cultivation condition on the quality of KDML105. Results showed that the cultivation condition played an important role in the development of cooking and eating quality of KDML105. The difference between the two varieties was obviously observed in cooked form of rice. HCW was lower in length and width expansion but higher in volume expansion than KDML105. Regard to texture of cooked rice, HCW was lower in stickiness and cohesiveness of mass but harder and higher in chewiness, toothpack, and loose particles than KDML105. Also, HCW was lower in AcPy concentration and intensity of cooked rice aroma than KDML105. Cooked rice flour of HCW was lower in peak, breakdown, final, and setback viscosity but required more time to reach the peak-viscosity than that of KDML105. Besides, HCW retrograded faster than KDML105. Doubtless, KDML105 was more preferable. Based on the difference in the characteristics, properties, and qualities between KDML105 and CNTI, effective methods selected for identification of CNTI (high amylose and non-aromatic rice) mixed with KDML105 (zero, 25, 50, 75, and 100% of CNTI in KDML105) were alkali digestibility test (Only grain of KDML105 completely dispersed after immersion in 1.7%KOH for 23 hours.), dye-staining method (KDML105 stained pink but CNTI stained dark purple with iodine solution.), glass plate-white center method (CNTI, required 21 minute-cooking, did not gelatinize with cooking time of KDML105, 17 minutes.), back extrusion test (CNT1 was very harder than KDML105 and the negative correlation with high R2, 0.9947, between hardness and the ratio of KDML105 was observed.), and descriptive test of cooked rice texture (Stickiness, cohesiveness of mass, and toothpack were positively related to the ratio of KDML105 while hardness and chewiness were negatively related.). For identification of PTTI (low amylose and aromatic rice) mixed with KDML105 (zero, 25, 50, 75, and 100% of PTT1 in KDML105), the useable methods were dyestaining method (KDML105 stained pink but PTT1 stained light pink with iodine solution), back extrusion test (PTT1 was lower than KDML105 and the positive correlation with high R2, 0.9937, between hardness and the ratio of KDML105 was also observed.), descriptive test of rice texture (Stickiness, cohesiveness of mass, toothpack, and loose particle were negatively related to the ratio of KDML105 while hardness was positively correlated.), quantitative analysis of AcPy concentration (KD-NML105 was twice as concentrated as PTTI and the AcPy concentration was positively related with the ratio of KDML105.), slow retrogradation of cooked rice (PTT1 retrograded faster than KDML105 by showing opaque grain after cooling for 24 hours), and DNA based cultivar identification. Among the methods for identification of other Thai rice varieties mixed with KDML105, the dye-staining method was considered best. Not only did it be practical method, but it was also rapid (only three minutes), economize, without of instrumental requirement and could be used to distinguish whether high or low amylose mixed with KDML105. However, for export market or international requirement, the DNA based cultivar identification was still confided to investigate the adulterate varieties in KDML105. Whiteness, cooking time, volume expansion of cooked rice, and cooked rice texture apparently changed during three-month storage under artificial aging. The R2 values from the relationships of whiteness and hardness with storage duration of all the varieties were higher than 0.8 while these values from the relationships of the other qualities were varied. The whiteness, cooking time, volume expansion, and hardness of all the rice variety were increased with the increase in storage duration. High amylose rice (CNT 1) changed more in whiteness but less in cooked rice hardness than low amylose rices (KDML105, HCW, and PTTI). Additionally, by using triangle test, three-month aged rice of each the variety was considerably different from its freshly harvested rice. |
| Year | 2006 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. FB-06-17 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Athapol Noomhorm |
| Examination Committee(s) | Rakshit, Sudip Kumar; Salokhe, Vilas M. |
| Scholarship Donor(s) | RTG Fellowship |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2006 |