Thermal processing effect on the quality of cooked brown and parboiled rice in retortable pouches | |
| Author | Arunothai Puangmanee |
| Call Number | AIT Thesis no.FB-05-11 |
| Subject(s) | Retort pouches Rice, Parboiled Brown rice |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. FB-05-11 |
| Abstract | The lab scaled hot water immersion retort was designed and developed for sterilization of cooked rice in the retortable pouch. The milled rice of KDML 105 and parboiled rice with 10-min boiling representing as the partially cooked rice samples for preliminary trials were conducted to achieve the thermal process at 116°C, 20 min. The mass average sterilizing value (Fo) gained was about 3.09 min and 2.81 min, respectively for KDML 105 and parboiled rice. To overcome FO value of cooked brown and parboiled rice of about 3 min, the processing time would be extended to 25 min as the constant retort temperature of 116°C. Brown and parboiled rice were subjected to precook by two hydration pretreatments prior to thermal processing in order to accomplish the textural properties of retorted cooked rice as identical to the freshly cooked rice samples (references) prepared by an automatic rice cooker. Brown rice was partially cooked by 40-min soaking and 14-min boiling (pretreatment 1) and 19-min boiling (pretreatment 2). Parboiled rice, on the other hand, was processed by 35-min soaking and 13-min boiling (pretreatment 1) and 17-min boiling (pretreatment 2). Brown and parboiled rice with the two pretreatments obtained 64+1% and 67+1% moisture content, respectively, as similar to the final moisture content of the references. The results showed that parboiled rice had greater length, elongation and expansion than brown rice, whereas different pretreatment did not affect the grain appearances of both kinds of rice. In order to obtain the seal integrity and prevent shape distortion, sample size of 130 g and vacuum level of 40 % was found to be satisfactory for the two types of rice with the two pretreatments after heat treatment process. The thermal processing of 116°C, 25 min provided product stability in terms of microbial count and acceptable eating quality. At appropriate heat treatment, retorted cooked brown rice had FO values of 3.07+0.17 min and 324+0.15 min, respectively for pretreatment land 2, while FO values of retorted parboiled rice were 3.66±0.12 min and 3.85+0.07 min, respectively for pretreatment 1 and 2. The two types of rice with the two pretreatments packed in stand-up flexible pouches were then stored at ambient temperature for 3 months to monitor the changes in cooked rice quality. During storage, the moisture content and color still remained constant for all pouches. However, hardness values of all samples increased and were dependent on type of rice and pretreatment process. Subsequently, the reheating process using microwave and boiling water was determined to obtain the cooked rice texture nearly close to the references and maintain the serving temperature before eating. Aged retorted rice from all samples required 1-min microwave heating time. Another reheating method, boiling water reheating was observed to be suitable after 3.5 and 4.5 min, respectively for retorted brown rice of pretreatment 1 and 2, while retorted parboiled rice of the two pretreatments required 6.0 and 7.5 min, respectively. Different reheating technique, characteristics of retorted rice samples from the two pretreatments were not distinguished by trained panel. In order to stimulate the extent of retrogradation, the freshly cooked and retorted brown rice were stored at various conditions. The results indicated that the freshly cooked rice after 1-day refrigerated storage had the highest setback value (29.02+0.11 RVU) and the hardest texture (5.37+0.06 Kg). Nevertheless, the texture of the sample after microwave reheating was equal to that of the freshly cooked brown rice (control). Among all retorted brown rice samples with pretreatment 2, the highest setback value (17.09±0.53 RVU) was acquired by the retorted rice after 1-month ambient storage. The unaged retorted brown rice with 1-min microwave reheating appeared the hardest texture (5.28±0.09 Kg). Nonetheless, the two retorted rice samples after being reheated could not obtain the hardness close to the control |
| Year | 2005 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. FB-05-11 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Athapol Noomhorm; |
| Examination Committee(s) | Jindal, Vinod K. ;Rakshit, Sudip K. ; |
| Scholarship Donor(s) | Royal Thai Government Fellowship ; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2005 |