The study of optimum rice cooking methods developed for aseptic cooked rice | |
| Author | Kamolrat Sakullertpasuk |
| Call Number | AIT Thesis no.FB-06-16 |
| Subject(s) | Rice--Processing 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-06-16 |
| Abstract | KDML 105 has been known as one of the world famous reputation in appearance, cooking texture and aroma. The hydration behaviors during soaking and boiling affect the qualities of cooked KDML 105 rice which are mainly concerned with texture and moisture content. KDML 105 can be cooked by several methods, but the same palatability of cooked rice can be achieved by adjusting the amount of water and cooking time. To preserve the high qualities of cooked rice, thermal processes such as canning and retorting can be applied. However, the aseptic process was developed as a new trend in extending the storage life of cooked rice which provided better qualities than the conventional thermal processes. The KDML 105 rice was used in this study contained the moisture at 12.10±0.005 w.b. It was defined as low amylase rice with the amylose content 16.11±0.11%, gel consistency 75.8±0.15 nom and alkali spreading value at level 7.0. This rice with 2.10±0.06, 7.32±0.15, 13.43±0.48, 17.64±0.35 in width, length, area and perimeter, respectively, completely gelatinized in boiling water at 18 minutes. Its hydration behaviors in soaking and boiling affecting the gelatinization in rice grains were explained by semi-theoretical equations based on Fick's law of diffusion, and the proper soaking and boiling time were 30 and 5 minutes, respectively. However, waterto-rice ratio («'R) and the amount of rice (A) also played the important roles in the texture of cooked rice, more prominently in hardness which can be predicted by the linear regression equation at R- = 0.9834. The KDML 105 rice can be cooked with several methods such as with gas, steaming, microwave oven or pressure cooker which spent 21, 36, 19 and 14 minutes cooking 100 g of rice, respectively. Gas can cook rice founded on bubbles creation which is practical for all types of rice, but this method is susceptible to overcooking at the bottom ofa cooker. Cooking with steaming is milder because the heating medium is the vapor coming from boiled water which does not burn the rice. Nevertheless, vapor formation causes time-consuming while microwave oven based on its electric fields and the polar molecules in food spends less time cooking rice. Although it takes the advantage on shorter cooking time, water loss resulting from vigorously boiled water still occurs. Therefore, it requires more water for cooking, whereas this necessity does not exist in cooking with a pressure cooker. Moreover, not only is less water added, but also rapidness in cooking can be evidently observed since this cooker operates under pressure with a very tight closer. Despite these cooking methods are supported with different theories, they exhibited the similar tendencies with varied water-to-rice ratios. The hardness, dimensions and moisture content of cooked rice increased with the water-to-rice ratios. Furthermore, at the different layers of cooked rice in a 600 nil beaker, cooked rice at the top of beaker was harder, less sticky, smaller and less moist than middle and bottom. Nevertheless, the similar palatability of cooked rice can be achieved by adjusting the water-to-rice ratios which are appropriate for each method. In cooking 100 g of rice with the water-to-rice ratio 1.80, 1.72, 1.78 and 1.14 for gas, steaming, microwave and pressure cooker methods, respectively, they presented the high qualities of cooked rice among texture (hardness and stickiness), moisture content as well as the preference and acceptability scores in the sensory test. To preserve the qualities of cooked rice without the detrimental from microorganisms, thermal processing has been applied to manufacture canned rice or retort pouch rice. In this study, a new process namely aseptic process was developed to satisfy better qualities of cooked rice. From the outset, an aseptic chamber was designed in two patterns: firstly for atmospheric cooking and latter developed for under pressure cooking. From the former, KDML 105 was cooked in glass bottles at the maximum temperature at 100 °C in cooking part and then was transferred to packing part to close lids. After 7 and 14 days of incubation at 55°C and 37°C, the products showed unacceptable features with bad smell and sodden rice caused from the spores of spoilage bacteria, although the initial ones were not detected. Consequently, the process was developed for under pressure operation by modification of the aseptic chamber as the packing section under sterile atmosphere. This developed aseptic process was performed in the steam retort with 1.3 bar of pressure and it provided the highest temperature inside the chamber at 121 °C. The most proper conditions (116 °C, 1 minute) which granted the F° at 3.96 minutes can improve the cooked rice qualities (texture, dimensions, color and moisture content) compared among canned rice (F°= 4.56) and retort pouch rice (F0= 3.94). In addition, in safety point of' view, the aseptic cooked rice satisfied the approval of IFRPD in incubation test, total plate count, flat sour, mesophilics, thermophilics and sulfide spoilage. Furthermore, the aseptic cooked rice at 0 and 15 days (at 37 °C) were objectively and subjectively compared with the commercial canned rice (KhunPerm Canned Jasmine Rice). The results were obviously noticed that the aseptic cooked rice was superior than KhunPerm canned rice in every attribute. Additionally, since the aseptic cooked rice at 15 day of incubation did not differ from fresh aseptic cooked rice (0 day), the shelf life can be briefly assumed longer than 15 days. |
| Year | 2006 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ;no. FB-06-16 |
| 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, V. M.; |
| Scholarship Donor(s) | RTG Fellowship ; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2006 |