2.1. Rice Oil Yield
Rice contains considerable amount of oil with impressive functional food properties. In the present experiments, rice oils produced from the brown rice seed (unpolished rice), were evaluated for oil yields. The results in Figure 1
show that among rice varieties tested there is a significant (p
< 0.05) difference observed for the amounts of crude oil. The hexane-extracted oil yield from the tested varieties of rice varied from 1.92 g/100g (Basmati 385) to 2.72 g/100 g (Basmati 370). In close agreement to the data of our analysis, Boonsit et al.,
] also reported almost similar values, in the range of 2.00–3.07 g/100 g, for Malaysian rice. On the other hand, a study performed by Przybylski et al.
] on North American wild rice (Zizania palustris
), revealed the amounts of total lipids in the range of 0.7 to 1.1% showing that wild rice has considerably lower values as compared to regular rice (Oryza sativa
L). Nutritionally, among the rice varieties tested in the present study, Basmati 370 offered the highest lipid yield.
2.2. Fatty Acid (FA) Contents of Rice
Rice oil samples, extracted using n
-hexane were analyzed by gas liquid chromatography (GLC) after derivatizing into fatty acid methyl esters (FAMEs) and the data thus used to express the FA amounts on rice seed basis. The results presented in Table 1
depict the FA contents of different rice cultivars. There were seven saturated (C14:0
) and unsaturated (C18:1
) FAs detected in the rice varieties tested. The contents of saturated fatty acids (SFA) including myristic (C14:0
), palmitic (C16:0
) and stearic (C18:0
) acids in the rice ranged from 122–388 mg/kg, 3575–4961 mg/kg and 918–1602 mg/kg, respectively. The levels of unsaturated fatty acids (USFA) namely C18:1
(oleic acid), C18:2
(linoleic acid), C18:3
(linolenic acid) and C20:1
(gadoleic acid) ranged from 7042–10952 mg/kg, 5454–7028 mg/kg, 51–1550 mg/kg and 294–1177 mg/kg, respectively. It is evident that rice mainly contained oleic acid followed by linoleic acid. The composition of saturated and unsaturated fatty acids in different rice cultivars investigated in the present analysis closely resembled to that reported earlier by Anwar et al.
] for four Basmati varieties of rice indigenous to Pakistan. The composition of SFA of the investigated varieties of rice was quite comparable with those of palm kernel, cottonseed and avocado seed oils [40
]. The concentrations of major fatty acids C18:2
of the investigated rice varieties were in close agreement with those reported by Hemavathy and Prabhakar [41
] for the rice bran lipids from Indian based rice. However, the amount of C16:0
in the tested rice cultivars varied to some extent to those investigated by Hemavathy and Prabhakar [41
]. The fatty acid composition of investigated rice resembled in the content of C18:1
with that of rice indigenous to Pakistan [16
] however, varied to some extent with regard to other fatty acids.
The total contents, calculated on rice seed weight basis, of fatty acids, in the tested varieties of rice were highest in Basmati Pak (25840 mg/kg) while lowest in Basmati 370 (18,240 mg/kg). Lilitchan et al.
] investigated the total amount of fatty acids in rice of Thailand in the range of 18000–21000 mg/kg in rice, the values quite close to our present data. The total contents of fatty acids determined in the present work were also in line to those reported by Zhou et al.
] in three different varieties of Australian rice (22,500–28,000 mg/kg).
2.3. Phytosterols Content of Rice
According to Piironen and Lampi [44
], vegetable oils and their products are regarded as the rich natural sources of sterols, followed by cereal grains, cereal-based products and nuts. Plant sterols occur in cereals as free sterols, and in bound form as steryl esters of fatty acids and phenolic acids and glycosides. The phytosterol composition was analyzed using GC and GC-MS. β-Sitosterol with contribution varying from 446.2 mg/kg in Irri 6 to 656.4 mg/kg in Basmati Pak rice was established to be the major phytosterol component found in all the rice cultivars tested followed by campesterol, stigmasterol and Δ5
-avenasterol. The total contents of campesterol, stigmasterol and Δ5
-avenasterol in the rice cultivars ranged from 116.5–242.1 mg/kg, 75.3–181.0 mg/kg and 89.4–178.7 mg/kg. Cultivar Basmati Pak not only contained maximum content of β-sitosterol but also contained high amount of other three phytosterols. It is observed that Basmati Pak contained higher sterol contents relative to other cvs. (Table 2
). Phytosterols play a positive role in reducing absorption of cholesterol and reducing the level of negative lipoproteins in human blood, thus potentially reducing the development of heart diseases [45
]. The dietary intake of natural phytosterols ranges between 150–450 mg/day depending on eating style of a person [46
]. In human diet β-sitosterol, campesterol and stigmasterol are the major and most common phytosterols distributed [47
As far as the total amount of sterols is concerned, the highest level (1323.4 mg/kg) was found in Basmati Pak and the lowest (739.4 mg/kg) in KSK-133. No quantitative data for the total sterol contents of rice is reported as such with which we can compare our present values. Toivo et al.
] reported total amount of rice sterols (7310 mg/kg of oil). Comparing the present rice phytosterol data (739.4–1323.4 mg/kg) with that of wheat having an amount of 600 mg/kg [48
], it is understandable that rice varieties tested are a rich source of these valuable components.
In the present study, β-sitosterol, campesterol, stigmasterol and Δ5
-avenasterol were found to be the main rice phytosterols which could be supported by some earlier studies. Kuroda et al.
] isolated and analyzed sterols from rice bran oil and reported β-sitosterol, campesterol, and stigmasterol as predominant sterol components. Gaydou and Raonizafinimanana, [50
] investigated Malagasy rice bran oils for sterol composition and found eight different sterols with β-sitosterol (53–59%), campesterol (16–26%) and stigmasterol (10–13%) as the predominant components. From the given discussion, it can be assumed that rice is a potential source of natural phytosterols to imparting health benefits. Vissers et al.
] reported that 2.1 g sterols/day, derived from rice bran oil, can decrease LDL cholesterol by 9% and serum total cholesterol by 5% in normolipemic humans.
Tocopherols provide protection to lipids against free radicals through their radical scavenging action [52
]. Tocopherols, recognized as vitamin E isomers and having lipophilic property, are mainly present in the pericarp and endosperm part of cereal caryopses [53
The composition of tocopherols [alpha-, gamma- and delta-tocopherols] in the tested varieties of rice was determined using high performance liquid chromatography (HPLC). The contents of different tocopherols, expressed on rice seed weight basis, in the selected varieties of rice is shown in Table 3
. All the varieties tested revealed the presence of α-, γ- and δ- tocopherols. It is evident that concentration of α-tocopherol was comparatively higher than other isomers of tocopherols. The maximum value of γ-tocopherol (76.1 mg/kg of rice seed) was found in Basmati Pak and minimum (39.0 mg/kg of rice seed) in Irri-6. The content of γ-tocopherol in the selected varieties of rice was minimum (20.5 mg/kg of rice seed) in KS 282 and maximum (28.1 mg/kg of rice seed) in Basmati 198. The analysis revealed the amount of δ-tocopherol to be the highest in Basmati 370 (16.5 mg/kg of rice seed) while the lowest in Irri6 (6.5 mg/kg of rice seed). The total tocopherol content comprising α-, γ- and δ-tocopherols ranged from 67.1 mg/kg of rice seed (Irri6) to 115.3 mg/kg of rice seed (Basmati Pak). Basmati Pak was found to be the best variety regarding the amount of tocopherols. The selected varieties of rice were found to be a potential source of α-, γ- and δ-tocopherols whereas β-tocopherol was not detected. It is widely accepted that δ-tocopherol has greater antioxidant potency than that of γ- or α-tocopherol [54
]. Yawadio et al.
] studied the black pigmented rice and detected four isomers of tocopherols (α-, β-, γ-, δ-) with total contents as70 mg/kg. Rice bran contains over 300 mg/kg of vitamin E [23
Rice (Oryza sativa
) is one of the rich natural sources of vitamin E like tocopherols and tocotrienols, containing wholesome amount up to levels as high as 300 mg/kg [23
]. Approximately 1.0% of the unsaponifiable fraction of rice oil is α-tocopherol. Studies show that 1.0 g of oil contains 3.0 mg of α-tocopherol [56
]. Due to presence of considerable amounts of natural antioxidants such as tocopherols, rice oil is worthwhile to improving the storage and frying stability of oils [57
]. Ha et al.
] examined the effect of degree of milling on tocopherols in rice and found that total tocopherol contents of rice samples after milling were very low (37.7 mg/kg) indicating that the removal of the hull and milling process reduced the content of tocopherols.
γ-Oryzanol, a commonly found bioactive component in rice, is rarely found in other cereals and vegetables. Generally, crude rice oil contains more than 2% unsaponifiable matter comprising mainly γ-oryzanol along with phytosterols and tocopherols etc.
]. The antioxidant activity of γ-oryzanol can be attributed to its structure, which includes ferulic acid with strong antioxidant activity [32
]. Rice bran oil contains about 3000 mg/kg of γ-oryzanol, which is a mixture of several components of ferulate esters of triterpene alcohol [61
γ-Oryzanol contents in the tested varieties of rice were analyzed rice lipids using HPLC and calculations made on rice seed weight basis Table 4
. The composition of γ-oryzanol (mg/kg of brown seed rice) of different varieties of rice revealed the presence of four different components of γ-oryzanol including those of cycloartenyl ferulate, 24-methylene cycloartanyl ferulate, campesteryl ferulate and β-sitosteryl ferulate. The amounts of these components mostly varied (p
< 0.05) among selected varieties of rice. The levels of principal component, 24-methylene cycloartanyl ferulate, among the rice varieties tested varied from 140.8–183.1 mg/kg. The content of second major compound i.e
. cycloartenyl ferulate was found to be maximum (103.6 mg/kg) in Basmati Pak and minimum (65.5 mg/kg) in KSK-133. Campesteryl ferulate, the third main component detected, ranged from 29–45 mg/kg, while the least prevalent compound namely β-sitosteryl ferulate was 8.56–10.42 mg/kg. Overall, the contents of the detected γ-oryzanol components were higher in the Basmati varieties of rice (Basmati Pak, Basmati Super and Basmati 370) revealing their higher antioxidant and functional food potential. The other varieties tested also contained considerable levels of γ-oryzanol. The total amounts (mg/kg of rice seed) of γ-oryzanol among varieties of rice tested varied from 246.7–330.3 mg/kg. Basmati Pak was found to be the best variety with regard to the amount of γ-oryzanol.
Several earlier studies support our present data on rice γ-oryzanol. Xu and Godber, [62
] extracted γ-oryzanol from rice yielding a maximum of 1.68 mg/g of rice. Norton, [63
] reported that the oryzanol group is unique in rice and the exact composition of oryzanol depends on rice cultivars. Almost 10 different fractions of γ-oryzanol isomers from rice have been successfully identified and isolated using a reverse-phase HPLC [64
]. According to some reports, the contents of γ-oryzanol (115–780 mg/kg) differ with the source of rice, depending on the degree of processing [31
]. Azrina et al.
] analyzed oryzanol in rice and the values determined were in agreement with those of the present study. The rice processing methods may affect oryzanol contents and a major part of this valuable compound is lost during the oil refining process [21
Overall, on the basis of the amounts of high-value bioactive components investigated such as essential fatty acids, tocopherols, phytosterols and γ-oryzanol, the Basmati varieties, especially Basmati Pak was established to be relatively the superior variety among others, suggesting its potential uses as ingredients of functional foods and nutraceuticals to benefit health of consumers and promoting value-addition.