Modification of low amylose rice flour and starch by extrusion cooking and drum drying | |
| Author | Panuwat Supprung |
| Call Number | AIT Diss. no.PH-04-02 |
| Subject(s) | Rice flour--Extrusion Starch--Extrusion Amylases |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. PH-04-02 |
| Abstract | In this study, low amylose rice flour and starch were physically modified into pregelatinized flour and starch powder form through extrusion cooking and drum drying processes. The effects of processing conditions on of rice flour and starch were investigated, and the possible meaningful correlation between process parameters and functional properties in the form of predictive models for general application were established. Thai aromatic rice (variety: KDML 105) flour was prepared from broken rice by wet milling method and rice starch was prepared by alkaline method. Effects of single screw extrusion operating conditions namely barrel temperature (140-200°C), screw speed (150-250 rpm) and feed moisture content ( 16 to 28 % wb) on the expansion ratios (ER), initial peak viscosity (IPV), water absorption index (W Al), water solubility index (WSI) and degree of gelatinization (DG) of rice flour and starch extrudate were investigated. Result showed that high feed moisture content of flour and starch led to a decrease in ER and WSI and an increase in IPV, WAI and DG. Barrel temperature and screw speed had no significant effect on all properties. The ER, DG, WSI and WAI of extruded starch were slightly higher than flour, but IPV of extruded starch was lower. All functional properties of extruded flour and starch were highly correlated (R2 =0.737 to 0.949) with the extrusion cooking conditions in terms of feed moisture content, barrel temperature and screw speed. Double drum dryer was used to produce pregelatinized flour and starch. The effects of drying conditions including solid content of slurry (20-40 o/ow/w), holding time (14- 84sec) and surface temperature (115-135°C) were also investigated. Results revealed that moisture content (MC), WAI, WSI, DG and IPV values of high solid content led to a decrease in holding time and resulted in a decrease in WAI, IPV and DG while MC and WSI increased. High surface temperature led to a slight decrease in IPV values. The DG, WAI and WSI values of drum dried flour were lower than that of dried starch but IPV value was higher. All functional properties of drum dried flour and starch were highly correlated (R2 =0.683 to 0.926) with the solid content, holding time and surface temperature. The product properties of both methods, extruded flour and starch showed lower WAI and IPV values than drum dried samples, whereas the WSI value was higher. The DG values of drum dried samples was a nonsignificantly higher than those of the extruded samples. Scanning electron micrographs showed that the particles of extruded starch powder had complex forms with surface cracks. Drum dried starch particles looked like flakes and the shape was not uniform. Drum drying improved the freeze-thaw stability of sample paste, however this property was the opposite for extruded samples. The WAI of pregelatinized flour and starch for difference water temperature of 25, 45, 65 and 85°C showed that as the temperature increased, the WAI of drum dried flour and starch increased whereas WAI of native samples increased at temperature above 45°C. In contrast, WAI of both extruded samples decreased whereas WSI increased markedly with increasing cooking temperature. High temperature induced stronger pseudoplastic behavior of pregelatinized starch pastes and showed poor freeze-thaw stability. The effects of the addition of sugar (10 to 50 o/ow/v), lipid (0.07 to 0.98 % w/v) and protein (5 to 40 % w/w) were also investigated. WAI of native and pregelatinized flour and starch decreased slightly with an increase in the sugar, lipid and protein concentration. The IPV of pregelatinized flour and starch showed viscosity development with an increase in the sugar lll and protein concentrations. Consistency of drum dried sample pastes increased with increasing lipid and protein concentrations but the results showed the opposite for extruded samples. Increasing protein induced stronger pseudoplastic behavior of extruded pastes but the result showed the opposite with an increase the lipid concentration. Increasing sugar (10 to 30 %w/v), protein and lipid (0 to 0.21 %w/v) concentrations improved freeze-thaw stability of native and pregelatinized flour and starch, with the exception of the addition of lipid to drum dried samples. Instant mushroom soups were prepared with 12 % w/w of extruded and 5.5 % w/w of drum dried flour and starch at water temperature of 25 and 70°C. Soup was given a high sensory score by panelists (6.58 to 7.08, like slightly to like moderately) and showed no significant difference among native flour, starch and commercial soups. |
| Year | 2004 |
| Corresponding Series Added Entry | Asian Institute of Technology.|tDissertation ; no. PH-04-02 |
| Type | Dissertation |
| 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. ;Ranamukhaarachchi, S.L.; |
| Scholarship Donor(s) | Rajamangala Institute of Technology; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2004 |