Improvement of rice flavor with natural Pandan extract | |
| Author | Natta Laohakunjit |
| Call Number | AIT DISS. no. PH-03-05 |
| Subject(s) | Rice Flavor |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Teclmical Science |
| Publisher | Asian Institute of Technology |
| Abstract | Flavor of pandan (Pandanus amaryllifolius Roxb.) leaves was extracted by three methods: supercritical fluid extraction with C02 (SC-C02), simultaneous steam distillation/extraction (SDE), and ethanol extraction. The quality and yield of 2-acetyl-1- pyrroline (ACPY) which resembled the main volatile compound of aromatic rice were compared. The SC-C02 extraction method at different conditions of pressure, temperature and contact time resulted in fomteen volatile compounds on the gas chromatogram, with ACPY and 3-methyl-2(5H)-furanone as predominant constituents. The interaction of extraction conditions significantly influenced yield of ACPY and other volatiles. There is a potential for high yield of ACPY by SC-C02 at 200 bar, 50°C and 20 min. The SDE-ether extract yielded small amount of ACPY and an undesirable odor while the dark green ethanol extract gave the highest ACPY yield as well as 3-methyl-2(5H)-furanone. At least 34 new volatile components were discovered from the three extraction methods. Binding of volatiles to three types of starch, namely, non-waxy rice, waxy rice and cassava starches, was high with diacetyl, cis 3-hexanol, and aldehyde C 10. Lower binding percentage with 2,4,6-collidine and ACPY of pandan extract was noted. Volatile binding occurred within 15 min, with about 50-60% of the compounds bound to rice starch. The effect of plasticizers such as glycerol, sorbitol and poly( ethyleneglycol) 400 (PEG 400), on mechanical and barrier properties of rice starch film was also investigated. Sorbitol and glycerol plasticized starch films were transparent and smooth, and had less insoluble particles compared to unplasticized films. PEG 400 did not improve rice starch film property. Higher concentration of glycerol and sorbitol increased film softness and stickiness. Addition of 35% w/w glycerol and 45% w/w sorbitol resulted in higher solubility compared to unplasticized film. With increasing concentration of plasticizers, film tensile strength decreased. Although glycerol-plasticized films had significantly lower tensile strengths than sorbitol treated films, their elongation-at-break was higher. Moreover, water vapor transmission rate (WVTR) through plasticized films increased with glycerol and sorbitol contents, with glycerol-plasticized film having higher WVTR than sorbitol-plasticized film. Sorbitol-plasticized film exhibited lower oxygen transmission rate (OTR) than glycerolplasticized films. Due to its higher tensile strength and lower OTR and WVTR, the 30% sorbitol-plasticized film was selected for flavor-emiched coating ofrice kernel. Three non-aromatic rices, an intermediate amylose rice of RD 23, high amylose rice of Supanburi 1 (SPR 1), and Supanburi 90 (SPR 90) were coated with 30% sorbitol plasticized iice starch entrapped with pandan extract and stored for 6 months. The characteristics of coated non-aromatic rice were compared to uncoated non-aromatic and 3 aromatic rices, Khao Dawk Mali 105 (KDML 105), Klong-Luang (KL) and Patumthani 1 (PTT 1). Appearance of the coated rice was not noticeably different from non-coated rice. However, scanning electron microscopy showed that the surface of coated rice appeared more homogeneous, clearer and smoother than non-coated rice. GC-MS analysis revealed 9 major volatiles; toluene, nhexanal, ethylbenzene, l-methoxy-2-butene, 2-ethenyloxypropane, 2-hexanol, (E)-2 heptanal, ACPY, and nonanal, in aromatic rices as well as non-aromatic RD 23, SPR 1 and SPR 90 rices coated with pandan extract. Non-aromatic rice coated with pandan extract contained greater ACPY than uncoated rices. During 6 months of storage, ACPY decreased. The ACPY content of pandan extract-coated non-aromatic rice did not significantly differ from that of aromatic rice KDML 105 and KL. n-Hexanal of coated non-aromatic rice was 3 times lower than that of uncoated non-aromatic rices and aromatic rices. The rate of free fatty acid (FF A) and thiobarbituric acid (TBA) development of coated non-aromatic rices was less than that of the uncoated non-aromatic rices and aromatic rice due to barrier properties of the film. During storage, hardness of coated rices in all treatments increased especially on the 61 h month. The yellowness (b value) of coated rices was higher than uncoated aromatic and uncoated non-aromatic rices. Whiteness of the uncoated non aromatic rice was higher than their coated treatments while whiteness of aromatic rices did not change during storage. Sensory quality analysis showed that non-aromatic rice coated with pandan extract did not significantly differ with that of uncoated rice in terms of appearance, color, aroma, softness and stickiness of cooked rice. When 6-month old aged rices cv KDML 105, RD 23, SPR 1 and SPR 90 were coated with pandan flavor extract, FFA and TBA content decreased while ACPY, starch content, whiteness, b value, hardness, and aroma of milled rice increased relative to uncoated rices. However, coating resulted in a reduction of acceptance and color scores. Furthermore, coating with pandan flavor extract of aged rices markedly improved aroma acceptance as compared with uncoated rices. Coated KDML 105 rice was most preferred but not significantly different with the coated RD 23 rice. The aroma and overall score of aged rices were improved by the addition of pandan extract. |
| Year | 2003 |
| 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 Noomhonn |
| Examination Committee(s) | Jindal, Vinod K.;Chettiyappan Visvanathan;Rakshit, Sudip K. |
| Scholarship Donor(s) | Government of Austria |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2003 |