Selected Quality Attributes of Fine Basmati Rice: Effect of Storage History and Varieties

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1 International Journal of Food Properties ISSN: (Print) (Online) Journal homepage: Selected Quality Attributes of Fine Basmati Rice: Effect of Storage History and Varieties M.S. Butt, F.M. Anjum, Salim-ur-Rehman, M. Tahir-Nadeem, M.K. Sharif & M. Anwer To cite this article: M.S. Butt, F.M. Anjum, Salim-ur-Rehman, M. Tahir-Nadeem, M.K. Sharif & M. Anwer (2008) Selected Quality Attributes of Fine Basmati Rice: Effect of Storage History and Varieties, International Journal of Food Properties, 11:3, To link to this article: Copyright Taylor and Francis Group, LLC Published online: 01 Aug Submit your article to this journal Article views: 408 Citing articles: 6 View citing articles Full Terms & Conditions of access and use can be found at

2 International Journal of Food Properties, 11: , 2008 Copyright Taylor & Francis Group, LLC ISSN: print / online DOI: / SELECTED QUALITY ATTRIBUTES OF FINE BASMATI RICE: EFFECT OF STORAGE HISTORY AND VARIETIES M.S. Butt 1, F.M. Anjum 1, Salim-ur-Rehman 1, M. Tahir-Nadeem 1, M.K. Sharif 1, and M. Anwer 2 1 National Institute of Food Science and Technology, University of Agriculture, Faisalabad, Pakistan 2 District Food Controller, Punjab Food Department, Punjab, India Storage period, temperature and moisture are the key traits, accountable for variation in chemical, cooking and sensory attributes of rice. The study of two promising varieties of fine Basmati rice stored at various temperatures revealed pronounced influence of storage on various quality traits i.e. volume expansion ratio, water absorption ratio, elongation ratio, alkali spreading value, amylose contents and sensory attributes. The cooking quality was affected significantly in the months following harvesting. Freshly harvested Basmati varieties (Basmati Super and Basmati-385) were aged for a period of sixteen weeks (4 months) at different temperatures (5, 25, 35, and 45 C). Aging of rice played imperative role in establishing the aforesaid quality traits. Storage condition resulted in increased moisture, water absorption ratio, volume expansion ratio and elongation ratio while amylose content and alkali spreading value of both rice varieties were decreased. The protein content showed insignificant differences. Storage of both varieties at 35 C gave best results for sensory attributes like taste and over all acceptability. Basmati Super showed better performance in cooking and eating quality than that of Basmati-385 during storage. Keywords: Aging, Temperature, Amylose, Cooking quality, Elongation ratio. INTRODUCTION Rice (Oryza sativa L.) occupies second position in production amongst the cereal crops on global basis. It is grown in many parts of the world but mainly concentrated in Asia. [1] It constitutes more than 50% of world s staple diet and contributes up to 70% of the dietary energy and protein requirement in the daily diet of about 2.5 billion of Asia. [2,3] Rice is not only a staple crop of Pakistan but also a major source of foreign exchange earning as much as one-third of the production that is exported every year. [4] Rice has been considered one of the best foods among all cereals for its nutritional quality. It has higher digestibility, biological value and protein efficiency ratio owning to presence of higher percentage of lysine than that of wheat. Minerals like calcium, magnesium, phosphorus and silicon are present along with some traces of iron, zinc, copper, and manganese. [5] In addition to the kernel, rice bran due to its overall composition, nutritional Received 21 March 2007; accepted 10 August Address correspondence to M.S. Butt, National Institute of Food Science and Technology, University of Agriculture, Faisalabad, Pakistan. drmsbutt@yahoo.com 698

3 QUALITY OF BASMATI RICE 699 profile, functional characterization, and apparent hypoallergenicity is being added in different food products that are in particular beneficial for those individuals who show allergenicity to other cereal grains. [6 8] Baked foods provide one of the most potential possibilities of utilizing rice bran in foods. Uses of rice bran are advocated in making breads, muffins, pan cakes, cookies, cakes, pies, extruded snacks, and breakfast cereals. [9 10] In South East Asia, most of the consumers prefer rice grains that become fluffy after cooking and retain their conformation without aggregation. Generally two types (coarse and fine) of rice are mostly cultivated. The coarse varieties (IRRI-6, KS-282) are non aromatic while fine varieties (Basmati-385, Basmati-386, and Basmati Super) are aromatic in nature. Freshly harvested rice (fine, coarse) give stickiness after cooking. Aging is a good remedial measure. Basmati rice with distinct flavor possesses characteristics of both indica and japonica varieties and may be considered as an intermediate group between the two. The consumers are interested in rice varieties with good cooking and eating qualities, which are largely dependent on physicochemical properties of starch that makes up 90% of milled rice. Basmati rice falls in the category of non-waxy, non-glutinous rice with intermediate amylose content and gelatinization temperature. Other important features like apparent amylose content, water absorption, volume expansion, and final starch gelatinization temperature collectively determine cooking and eating quality of rice. It also possesses medium gel strength, which is most preferred, as it cooks flaky and remains soft on cooling. [11] The freshly harvested rice cooks sticky, more solids are leached out during cooking, and it swells less as compared to aged rice. Significant changes occur in the cooking characteristics in the months following harvest because of number of physicochemical changes in the grain. Storage is an inevitable step that results in decreased cohesiveness, large volume and fine texture of the cooked rice. The cost of aged rice is normally 25 30% higher than fresh rice. [12] In domestic and international markets the quality of rice determines its market value and appeal. Various post harvest processing treatments have been found effective to improve its sensory and cooking attributes. Ageing is undoubtedly one of the best ways to achieve the desired objectives. During storage, a number of physicochemical and physiological changes occur, this is usually termed as ageing and it affects rice functionality and eating quality. For example, as rice aged, cooked rice texture became fluffy and harder, while the amount of leachate from cooked rice decreased. The leached amylose is mainly responsible for the viscosity of starch pastes. The ageing rendered the rice progressively more organized and resistant to swelling and disintegration. [13,14] The storage condition resulted in decreased aromatic compounds and an increase in the molecular weights of proteins, [15] improved head rice yield and cooking properties, [16] decreased amylose content, liquefaction number, water uptake, gruel solids loss, transition temperatures, enthalpy of gelatinization, peak height index and increased the free fatty acid content, cooking time, elongation ratio, packability, hardness, cohesiveness, extrudability, and chewiness. [17] Storage induced changes in the physicochemical properties of rice may be both desirable and undesirable depending on storage conditions, variety, and end-user requirements. Moisture content, storage temperature, and storage time are the key factors influencing the chemical, physical, and functional qualities of rice during post-harvest storage. The overall changes may depend on the variety, storing conditions, and further treatment; however, it is common consensus that aging of rice improves the eating quality. [18] The rate and nature of the change is primarily temperature dependent that activates the enzymatic

4 700 BUTT ET AL. reactions involving starch, protein, and lipid. Quality changes generally occur faster with increasing temperature and storage duration. Keeping in view the importance of rice quality, the project was planned to evaluate the role of different storage temperatures and intervals on the chemical, cooking, and sensory traits of promising fine Basmati rice varieties that will ultimately enhance the meticulousness regarding quality and certainly the export market. MATERIALS AND METHODS Materials and Storage Conditions Fine rice varieties (Basmati Super and Basmati-385) were procured from Reem Rice Mills. The rice varieties were stored in polythene bags at 5, 25, 35, and 45 C (Table 1). Both varieties were analyzed for various parameters during the study at 1 st (0 day), 4 th, 8 th, 12 th, and 16 th week of storage. Chemical Assay The rice samples were analyzed for moisture, crude protein, alkali spreading value and amylose content according to their respective methods. Proximate Analysis Basmati Super and Basmati-385 samples were analyzed on dry weight basis in triplicate for moisture and crude protein content at 0-, 4-, 8-, 12- and 16-week intervals. The moisture content of each sample was determined by drying 3 g sample in air forced draft oven at 105 ± 5 C according to AACC method No A. [19] For crude protein determination, the nitrogen content in each sample was determined by using Kjeltec System-II (Tecator AB, Hoganas, Sweden) based on Kjeldhal s method as described in AACC method No [19] The protein percentage was calculated by multiplying nitrogen percent with factor [20] Amylose Content Amylose content of rice varieties was determined on stated intervals by using spectrophotometerical technique. [21] For the standard curve, absorbance was measured at 620 nm with spectrophotometer (CE 7200). Absorbance values were plotted against the concentrations of anhydrous amylose (mg). A straight-line relationship was obtained as observed in Figure 1. Milled rice samples were ground to pass through a 100-mesh sieve. One hundred milligrams of sample in triplicate was transferred to 100 ml volumetric flasks and added carefully 1 ml of 95% ethanol and 9 ml of 1 N NaOH and then volumes were made up to 100 ml. Five ml of the starch solution was pipetted into a 100 ml volumetric flask and then 1 ml of 1 N acetic acid and 2 ml of iodine solution were added. Table 1 Treatments used in the study. Basmati Super Basmati-385 T 5 C T 25 C T 35 C T 45 C T 5 C T 25 C T 35 C T 45 C

5 QUALITY OF BASMATI RICE 701 Figure 1 Amylose standard curve. The solution was made up to volume with distilled water, shaken and allowed to stand for 20 min. Absorbance in each solution was taken as described in the preparation of standard curve. The dilution factor 20 for the sample was included in the conversion formula. Amylose content was determined by the following formula and expressed on dry weight basis. Amylose = Optical density Slope of the curve Dilution factor (1) Alkali Spreading Value Gelatinization temperature was determined by using alkali spreading value according to techniques described by Little et al. [22] at the mentioned storage periods (Table 2). For this purpose, six whole milled kernels of rice were spaced evenly in a petri dish, containing 1.7% KOH solution for 24 h. in incubator maintained at 30 C. The spreading of each kernel was rated on following 7-point numerical scale (Table 3). Table 2 Classification. Spreading scale Description 1 Kernel not effected 2 Kernel swollen 3 Kernel swollen, collar incomplete and narrow 4 Kernel swollen, collar complete and wide 5 Kernel split or segmented collar complete or wide 6 Kernel dispersed, merging with collar 7 All kernels dispersed and intermingled

6 702 BUTT ET AL. Table 3 7-point numerical scale. Rating Gelatinization temperature 1 2 High 2 3 High / intermediate 4 5 Intermediate 6 7 Low Volume Expansion Ratio and Water Absorption Ratio Volume expansion ratio was calculated every month as volume of cooked rice to volume of raw rice while water absorption ratio was determined by dividing the weight of cooked rice with that of raw rice. Ten g rice was taken in a 100-mL cylinder (in triplicate) already filled with 50 ml of water and the increase in volume was recorded as the volume of raw rice. Then all the samples were soaked for 30 min in water. After that, cooking was done in boiling water for 10 min. Immediately after cooking, water was drained out and cold water was added to cool them. Rice kernels were then completely drained out first by sieve then by filter paper, and the increase in volume was measured by cylinder as volume of raw rice was measured. [21] The two ratios were calculated by the formulae given below: Volume expansion ratio = Cooked rice volume Raw rice volume (2) Water absorption ratio = Cooked rice weight Raw rice weight (3) Elongation Ratio Elongation ratio was measured at 1 st (0 day), 4-, 8-, 12-, and 16-week interval by dividing the average length of cooked rice kernels with that of raw rice. [23] The elongation ratio was measured by the following expression: Average length of 10 cooked rice grains Elongation ratio = Average length of 10 raw rice grains (4) Sample Preparation for Sensory Evaluation Milled rice samples weighing 300 g were washed three times with enough distilled water to immerse them, and excess water was removed by means of straining. Rice samples were cooked in a household electric rice cooker. Proper care was taken in adjusting the amount of water in the cooking to compensate for the water remaining in the rice after washing and straining. After the rice cooker was automatically switched off, it was left on warm setting for an additional 10 min, and the rice pot was removed and cooled with cold water to room temperature (30 35 C). The top 1-cm layer of cooked rice was discarded

7 QUALITY OF BASMATI RICE 703 and samples for analysis were taken from the middle of the cooking bowl. Cooked rice was fluffed gently with a ladle and transferred into a glass container with a plastic lid for sensory evaluation. [12,24] Sensory Evaluation The trained taste panel was comprised of 10 members (five men and five women), each having more than 3 years of experience. Sensory evaluation was performed in air conditioned booths, the temperature maintained at F and 50% RH. The booths were positioned side by side with adequate lighting arrangement and were painted off white. The panelists rated the cooked rice for intensities of individual attributes including color, aroma, taste and texture using 9-point hedonic scale (1 = extremely low intensity and 9 = extremely high intensity). Color or whiteness was evaluated first as the surface quality of cooked rice. Aroma is perceived by the olfactory sense and was assessed by sniffing the cooked rice before putting into the mouth to evaluate taste and texture. Panelists were presented approximately 15 g of cooked rice samples of each treatment in coded glass cups with plastic lids in a random order for evaluation along with a glass of drinking water. Samples were served warm and the panelists cleaned their palates with water prior to testing a fresh sample. Two sessions one in the morning and another in the afternoon were arranged each day. The descriptive panel also rated the cooked rice samples for overall acceptability without any undue bias towards other sensory attributes. [25] Statistical Analysis Data obtained for each parameter was subjected to statistical analysis in order to find out the effect of various temperature treatments and storage periods on various characteristics of rice varieties. For the purpose analysis of variance (ANOVA) technique and Duncan s Multiple Range Test (DMRT) were applied by using the software program MSTAT-C [26] according to the method described by Steel et al. [27] RESULTS AND DISCUSSION The interaction between two varieties at various temperatures and storage intervals showed non-significant differences therefore, the pooled means have been discussed. Chemical Analysis Moisture content. Moisture plays an important role in determining the rice quality. High moisture content increases the microbial deterioration and spoilage during storage. Moisture content was significantly affected due to different storage temperatures and intervals. It is obvious from the results (Table 4) that significant difference exists for Basmati Super (9.19 g/100 g sample) and Basmati-385 (9.27 g/100 g sample). There was a gradual decrease in moisture content as the temperature increased. The mean value of moisture at T 5 C was highest (9.69 g/100 g sample) followed by T 25 C (9.48%) and the lowest value (9.21 g/100 g sample) was observed in T 45 C. Similarly the moisture content of fine rice varieties gradually decreased ( g/100 g sample) during 16 weeks storage (Table 4). Previously, it has been found that increase in storage duration decreased the moisture contents [28, 29] and a decrease of g/100 g sample was found during storage.[30]

8 704 BUTT ET AL. Table 4 Effect of temperature, storage and varieties on moisture, protein, amylose, and alkali spreading factor. Moisture content Protein content Amylose content Alkali spreading factor Varieties means Basmati Super a 22.91a 4.27a Bamati b 21.97b 3.75b Pooled means for Temperature T 5 C 9.69a a 4.10a T 25 C 9.48ab b 4.09a T 35 C 9.29b bc 4.02b T 45 C 9.21b b 3.94c Pooled means for aging 1 st week 9.65a a 4.17a 4 th week 9.57ab ab 4.12ab 8 th week 9.43ab bc 4.07b 12 th week 9.31ab cd 4.00c 16 th week 9.26b d 3.88d Protein content. Nutritional quality of rice depends largely upon its protein content. Protein affects texture, tenderness and cohesiveness of cooked rice. The results indicated a significant difference between the protein contents of fine varieties i.e and 7.81 g/100 g sample for Basmati Super and Basmati-385, respectively (Table 4). Protein content was not significantly affected due to treatments and storage. The results are in agreement with findings of Zhou et al. [18] and Yousaf [5] that protein content in the rice grains remains essentially unchanged during storage, although the chemical properties of the proteins can be altered substantially. Amylose content. Amylose content is an important criterion in determining the cooking and eating qualities of rice. The amylose content of fine rice varieties showed significant effect due to various treatments of temperatures and storage intervals. The results indicated a significant difference between the amylose contents of Basmati Super (22.91 g/100 g sample) and Basmati-385 (21.97 g/100 g sample). The amylose content of both varieties decreased as the temperature increased (Table 4). The mean value of amylose at T 5 C was the highest (22.81 g/100 g sample) and the lowest (22.01 g/100 g sample) at T 45 C. There was a gradual decrease in amylose content of fine rice varieties with increased storage duration from initiation of the study to 16 th week. The mean value of amylose during 1 st week was the highest (22.86 g/100 g sample), and the lowest (21.74 g/100 g sample) was at 16 weeks storage. The results are in conformity with the previous findings that amylose content of rice decreased as the storage period increased. The decrease in amylose content might be due to the fractional changes in its molecular weight which decreased during storage. [28,17] Alkali spreading value. It is an indirect method of determining the gelatinization temperature that is a range of temperatures within which starch starts to swell irreversibly in hot water with simultaneously loss of crystallinity. Lesser the alkali spreading value higher will be the gelatinization temperature. The alkali spreading value of fine rice varieties was affected considerably due to various temperature treatments and storage intervals. The mean values for Basmati Super and Basmati-385 were 4.27 and 3.75, respectively (Table 4). The alkali spreading value of varieties decreased gradually as the temperature increased. The mean value of alkali spreading value at T 5 C was the highest

9 QUALITY OF BASMATI RICE 705 (4.10) and lowest (3.94) at T 45 C (Table 4). Likewise the alkali spreading value of rice varieties also decreased as the storage duration increased. The mean value of alkali spreading value was highest (4.17) at 0 day (1 st week) storage and lowest (3.88) at 16 th week. The results are close to those of Sheng [31] and Daniels et al. [16] that gelatinization temperature significantly increased during storage at high temperatures. Fan and Marks [32] also found that rice stored at 38 C exhibited higher gelatinization temperatures than those stored at 4 and 21 C. Cooking Quality Water absorption ratio. Water absorption ratio is an imperative tool in determining the cooking and processing quality of rice. Different treatments and storage intervals had notable effects on the water absorption ratio of the two rice varieties. The results showed significant differences between Basmati Super (3.21) and Basmati-385 (3.06) for water absorption ratio (Table 5). The water absorption ratio of both fine varieties increased gradually with the increase in temperature. The mean value of water absorption ratio at T 5 C was the lowest (3.09) while the highest (3.21) at T 35 C with non-significant differences (3.17) at T 45 C. Similarly the water absorption ratio of fine rice varieties also increased as the storage duration increased (Table 5). The mean value of water absorption ratio at the initiation of study was lowest (2.99) and the highest (3.66) after 16 th week. The results are in close agreement with the findings of Pushpamma and Reddy [33] and Lee et al. [34] that water absorption of rice increased during storage as rice became hard and absorbed more water during cooking. The hardness of rice increased during the aging process, and this is due to the formation of amylose-lipid complexes, which made the aged rice harder and less prone to disintegration. [17] Volume expansion ratio. The volume expansion ratio of rice varieties was affected considerably due to treatments and storage. The results showed a significant difference between the volume expansion ratios of Basmati Super (4.42) and Basmati-385 (3.83). The mean values for volume revealed that the volume expansion ratio of two varieties increased gradually as the temperature increased (Table 5). It was lowest at T 5 C Table 5 Effect of temperature, storage, and varieties on water absorption, volume expansion and elongation ratio. Water absorption capacity Volume expansion ratio Elongation ratio Varieties means Basmati Super 3.21a 4.42a 2.29a Bamati b 3.83b 2.15b Pooled means for temperature T 5 C 3.09b 3.99b 2.19c T 25 C 3.15a 4.14ab 2.24b T 35 C 3.21a 4.17a 2.28b T 45 C 3.17a 4.20a 2.35a Pooled means for aging 1 st week 2.99d 3.88e 1.99e 4 th week 3.10c 3.95d 2.07d 8 th week 3.27b 4.18c 2.31c 12 th week 3.45a 4.30b 2.42b 16 th week 3.66a 4.37a 2.49a

10 706 BUTT ET AL. (3.99) and the highest (4.20) at T 45 C. The volume expansion ratio of fine rice varieties also increased as the storage duration increased. The mean value at 1 st week was the lowest (3.88) and the highest (4.37) after 16 th week. As there is more water uptake by the grains due to less protein-starch interactions during ageing therefore, a concomitant increase in the volume expansion was found with increase in storage time and temperature. The results are in line with the findings of Yousaf [5] and Daniels et al. [16] They found that volume expansion ratio of rice increased during storage. Increase in temperature significantly improved expansion ratio of rice grains from 5 7% at 4 C to 18 68% at [35, 36] 37 C. Elongation ratio. Elongation ratio is an important criterion in determining the cooking and eating quality of rice. The elongation ratio was significantly affected due to temperature treatments and storage intervals. There was significant difference for elongation ratio between the varieties. The mean values were 2.29 and 2.15 for Basmati Super and Basmati-385, respectively (Table 5). The means revealed that the elongation ratio of two varieties increased as the temperature increased (Table 5). The mean value of elongation ratio at T 5 C was the lowest (2.19) and highest (2.35) at T 45 C. Similarly, the elongation ratio of fine rice varieties increased as the storage duration increased. The mean value of elongation ratio at zero days was the lowest (1.99) and the highest (2.49) after 16 th week. The results are in conformity with the finding of Faruq et al. [37] who kept rice grains of the four varieties in airtight containers at different temperatures for a period of six months and reported that elongation ratio increased significantly due to storage. The differences in elongation between the two cultivars may be attributed to differences in amylose content. The rice with higher amylose content has been reported to have higher gelatinization temperature. Amylose content improves the capacity of starch granules to expand without collapsing because of its greater capacity to hydrogen bonding. [2] Sensory evaluation. Sensory evaluation is usually performed towards the end of product developments. It is carried out to access the reaction of judges towards the product, and they rate their liking on a scale. Results regarding sensory evaluation of fine rice varieties stored at different temperatures and storage intervals are discussed below. Color. Color plays an important role in the acceptability of any food product. Whiteness of cooked rice is preferred in South East Asian people. The color of rice varieties was significantly affected due to treatments and storage. Color of the rice grains turned yellowish during storage at all the storage temperatures; however deterioration in color was accelerated at slower rates when the rice varieties were stored at lower temperatures (Fig. 2A). Color of fine rice varieties was adversely affected as the storage duration increased (Fig. 3A). The results show significant difference between two varieties for color. However, in general whiteness was decreased with increase in storage temperature [35, 38] and storage interval which is in conformity with the previous findings. Aroma. Aroma plays a primary role in mining consumer appeal. It is the odor of a food product that comprises the volatiles perceived by the olfactory system from a substance. The amount of volatiles escaped from a product is affected by the temperature and the nature of the compounds. Volatility is also influenced by the condition of a surface: at a given temperature, more volatiles escape from a soft, porous and humid surface than those from a hard, smooth and dry one. Different temperature treatments and storage intervals showed significant effects on aroma of rice varieties. Aroma was improved with increased temperature and in T 35 C the rice varieties obtained maximum score for aroma, however in case of T 45 C it was affected inversely (Fig. 2B). As there is continuous loss of aromatic compounds from the grains and production of off odors at higher temperatures

11 QUALITY OF BASMATI RICE 707 A: Color C: Taste V1 V2 T5 C T25 C T35 C T45 C T5 C T25 C T35 C T45 C B: Aroma D: Texture T5 C T25 C T35 C T45 C T5 C T25 C T35 C T45 C E: Overall acceptability T5 C T25 C T35 C T45 C Figure 2 Impact of temperatures on sensory attributes of fine rice varieties Basmati Super (V 1 ) and Basmati-385 (V 2 ). therefore, a regular decrease in the aroma of rice grains was observed. The two rice varieties after long term storage got less score than the freshly harvested. Similar trend was observed for aroma after 16 weeks (Fig. 3B). The results are close to the finding of Barber [39] who observed the development of off-flavor in stored rice after cooking. Offflavor development was attributed to increase in the contents of carbonyl compounds and deterioration of unsaturated fatty acids. High temperature and long storage also resulted in odor deterioration Taste. The taste, i.e., gustatory perceptions, caused by soluble substances in the mouth, constitutes the second major component of flavor. It is detected by the taste buds of the tongue and mouth membranes primarily as sour, salty, sweet, and bitter. The taste is influenced by the texture, aroma and composition of the foods. In practice, the consumer does not distinguish consciously from aroma, but reacts subjectively to the combined effect of flavor. Well-polished rice retains its flavor for a longer period than did under-polished rice because the outer layers of the kernel contain the highest levels of oxidizable compounds that contribute to off flavors. Taste is an expression of intrinsic characteristics of the rice as influenced by the interaction of seed physiological processes with the ambient environment. The taste of fine rice varieties was significantly affected due to treatments and storage. There was linear relationship in taste and increased storage temperature (Fig. 2C). Maximum improvement in taste was observed in T 35 C whereas at further increase in temperature, non-significant declining trend was observed in taste by the judges. During 16 weeks storage, there was continuous taste development perceived by the judges. At the end of study, both varieties gained maximum score for taste (Fig. 3C). The results are corroborated with the findings of Fukai et al. [40] who observed similar behavior for taste.

12 708 BUTT ET AL. A: Color V1 V2 B: Aroma W1 W4 W8 W12 W16 W1 W4 W8 W12 W16 C: Taste D: Texture W1 W4 W8 W12 W16 W1 W4 W8 W12 W16 E: Overall acceptability W1 W4 W8 W12 W16 Figure 3 Impact of storage intervals on sensory attributes of fine rice varieties Basmati Super (V 1 ) and Basmati-385 (V 2 ). Texture. During storage, there was incessant enhancement in texture of both varieties with increased temperature. However at 35 C optimum improvement in rice textural properties was observed by the judges. Basmati super showed more improvement than that of Basmati-385 (Fig. 2D). Texture was improved due to aging that resulted in the modification of interactions among the components of grains that have positive effect on the textural properties of the rice varieties. In case of Basmati super after 12 weeks of storage there was somewhat stability in the texture whereas it went up in case of Basmati-385 (Fig. 3D). Rice textural properties changed significantly in the months following harvest. Many of the functional changes that occur during storage and influence cooking properties, such as cooking time, water uptake, and stickiness are caused by protein-starch interactions. The aging process especially at high storage temperatures results in fewer interactions between oryzenin and starch and/or its components (e.g., amylose). After cooking stickiness decreased during storage of both rice varieties especially at high temperatures. Daniel et al. and Zhou et al. [16,41] have described similar trends. They observed that texture of rice improved during storage at high temperatures. In another study, Chung and Meullenet [42] found that the improved texture of rice was due to changes in starch and protein interactions particularly after storage at higher temperatures. The changes in textural properties of cooked rice from both the cultivars during aging may also be due to formation of amylose-lipid complexes. These complexes made the aged rice harder and less prone to disintegration. It is also reasonable to speculate that the Basmati super rice with higher amylose content provided more favorable conditions for inter- or intra-molecular

13 QUALITY OF BASMATI RICE 709 interactions of starch with other components such as protein and lipids as compared to Basmati-385 that resulted in improved texture. [43] Overall acceptability. There was unremitting increase in overall acceptability of both fine rice varieties with increased temperature. Storage of rice resulted in higher overall acceptability at almost all the temperatures, nevertheless the rice kernels stored at 35 C gained maximum score for this parameter as compared to other treatments (Fig. 2E). At temperature higher than 35 C there was decreasing tendency towards acceptability. Likewise, storage affected the acceptability in almost similar pattern except that there was inclination towards stability for this trait both the varieties after 12 weeks of storage as non-significant differences were observed at 16 weeks (Fig. 3E). The results are in close concurrence with the previous findings. [17,35] that report improvement in rice cooking and eating qualities during storage. CONCLUSION Storage of the rice varieties at different temperatures showed pronounced effects on various quality traits. For quality improvement, storage at 35 C gave better results than the other temperatures. Due to aging the rice became fluffy and intact after cooking because of modifications in the protein-starch interactions that ultimately uplifted the eating quality. Sensory attributes especially texture, tastes and overall acceptability were significantly enhanced during the aging process. Basmati Super performed better than that of Basmati-385. REFERENCES 1. Anonymous. National workshop on rice research and extension. Feeding the extra millions by Bangladesh Rice Research Institute: Gazipur, Bangladesh. 2002; Juliano, B.O. Rice: Chemistry and Technology; Am. Assoc. of Cereal Chemists. Inc.: St. Paul MN, Juliano, B.O. Rice grain quality: Problems and challenges. Cereal Foods World 1990, 35, GOP (Government of Pakistan). Economic Survey of Pakistan. Economic Affairs Division: Govt. Pak, Islamabad, Yousaf, M. Study on some physicochemical characteristics affecting the cooking and eating qualities of some Pakistani rice varieties. M.Sc. Thesis, Dept. Food Technol. Univ. Agric. Faisalabad, Pakistan, Ajmal, M.; Butt, M.S.; Sharif, K.; Nasir, M.; Nadeem, M.T. Preparation of fiber and mineral enriched pan bread by using defatted rice bran. International Journal of Food Properties 2006, 6 (2), Gujral, H.S.; Mehta, S.; Sharma, I.S.; Goyal, P. Effect of wheat bran, coarse wheat flour and rice flour on the instrumental texture of cookies. International Journal of Food Properties 2003, 9 (4), Sidhu J.S.; Kabir Y.; Huffman F.G. Functional foods from cereal grains. International Journal of Food Properties 2007, 10, Sharma, H.R..; Chauhan, G.S.; Agrawal, K. Physico-chemical characteristics of rice bran processed by dry heating and extrusion cooking. International Journal of Food Properties 2004, 7 (3), Gujral, H.S.; Mehta, S.; Samra, I.S.; Goyal, P. Effect of wheat bran, coarse wheat flour, and rice flour on the instrumental texture of cookies. International Journal of Food Properties 2003, 6 (2),

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