The effect of thermal processing on the quality of cooked rice packaged in retort pouch | |
| Author | Saowanee Chokanankun |
| Call Number | AIT Thesis no.PH-01-4 |
| Subject(s) | Retort pouches Rice--Quality |
| 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 |
| Abstract | A process for preparing sterilized pouched rice of low amylose KDML 105 was studied. Without any hydration treatment, a raw milled rice, KDML 105, was mixed with an adequate water or fully cooked rice was packed in pouches. Uniform sterilized cooked rice product with structural integrity was not obtained. To overcome these difficulties, before sterilization the partially cooked rice was made by 2 hydrated pretreatments. One was a combination of 30-min soaking and subsequent 6-min cooking in boiling water (pretreatment I) while the other was I 0-min boiling without presoaking steps (pretreatment 2). Moisture content of both partially cooked rice samples was limited at 66±1 % as close to a final moisture content of freshly cooked rice (control) prepared by automatic rice cooker. The results showed that with presoaking treatment, the rice grain was noticeably greater in grain expansion and elongation ratio. In addition, at an equivalent stage of softness a final cooked texture of the soaked rice was less damaged due to a shorter cooking time required. To sterilize partially cooked rice packaged in stand-up flexible pouches, the effect of sample size (130 g, 135 g, 140 g, 145 g of the total weight) was also studied with different vacuum levels (30%, 40%, 50%, 60% and 70%) to provide seal integrity and prevent shape deviation after vacuum-sealed. Sample size of 140 g and vacuum level between 30-40% resulted in more acceptable for both pretreatments after retorting. The thermal process conditions of l 16°C, 25 min and 121°C, 15 min which provided an equivalent lethality (Fo value) of about 3.787±0.61 and 3.526±0.14, respectively, were carried out for product sterility. The improvement of texture and color qualities, including preference from panelists was achieved at the low temperature and longer time (116°C, 25 min) as compared to the attributes of freshly cooked rice. After heat treatment at this optimal thermal process, the experimental results indicated that texture of cooked pouched rice made by the pretreatment I was softer than that of freshly cooked rice (control). However, the texture of the cooked rice from pretreatment 2 was found to be close to the control. The sterilized pouched rice was then stored at ambient condition for 3 months to study the effect of storage on changes of quality attributes. During storage, the stability of the pouched rice from both pretreatments regarding the qualities in moisture content, color, firmness and stickiness still remained constant. However, a change in degree of retrogradation was observed by DSC (Differential Scanning Colorimeter) over 3-month aging. Enthapy (~H) from the pretreatment 2 was significantly increased to 2.881 Jig after storage for 3 months. Moreover, to prepare the pouched rice at the serving temperature by microwave and conventional boiling methods, the hardness of reheated rice at each timing period (1-5 min for microwave heating and 3-6.5 min for boiling) was evaluated. The comparable rice texture to that of freshly cooked rice (control) was acquired after I-min reheating by microwave and 3.5 min and 6 min by boiling water from the pretreatment I and the pretreatment 2, respectively. In overall preference of sensory evaluation, characteristics of reheated pouched rice from both pretreatments were not significantly different from the attributes of freshly cooked rice product as judged by panelists. |
| Year | 2001 |
| 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 | Postharvest and Food Process Engineering (PH) |
| Chairperson(s) | Athapol Noomhorm |
| Examination Committee(s) | Jindal, Vinod K. ;Rakshit, Sudip K. |
| Scholarship Donor(s) | King's Scholarship |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2001 |