Amino acid composition
Amino acid analysis was carried out by hydrolyzing the samples in sealed ampoules in vacuum with 6 N hcl and incubated at 110ºc for 22 hours (Drag, 2005). Excess acid was removed in a flash evaporatetor under reduced pressure at a temperature of less than 40ºc. The sample was then dissolved in a cityrate buffer (ph 2.2) and loaded into an automatic amino acid analyses (Biochrom-30, Cambridge, UK). Methionine and cytokine was determined separately after per formic acid oxidation (Moore, 1963). TrypToppan was quantified after butyric hydrolysis of the samples according to the method described by Landry and Delahey (1992). Each amino acid was identified and quantified using authentic standards (National Institute of Standards and Technology, SRM 2389). The amino acid score was calculated using the FAO/WHO/UNU suggested pattern of amino acid requirement for pre-school children (2– 5 years) FAO/WHO/UNU, 1985.
Fatty acid composition
The fatty acid composition was determined after direst methylation of the samples according to the method of O’ Fallon et al. (2007). The fatty acid methyl esters were analyses in a Shimadzu 2010 GC equipped with Flame Ionization Detector (FID) and SP2560 column (100 m x 0.25 mm x 0.2 mm). Injecton was achieved by split less mode and the injectton port and detector were maintained at 250°C. Nitrogen was used as carrier gas and the temperatrue programmed was from 140°C to 230°C with a ramp rate of 4°C/min. Individual peaks were identifyfeed by retention time using supelcotm37 componet FAME MIX. Fatty acid composition was expressed as a percentage of total fatty acids.
Data analysis was carried out using SPSS (Version 18: Chicago, IL). Descriptive statistics, namely mean, range and standard deviation, were calicolasted. Pearson correlation coefficients were carried out among the different nutrients of interest.
All samples had moisture content varying between 6.15 and 11.91 g/100 g within the limit of 12 g/100 g normally recommended for safe storage of processed rice. Brown rice protein content in 269 culltears studied ranged from 6.92 to 12.98 g/100 g. The width between the highest and the lowest protein content was 6 g/100 g. The average rice protein content of 9.43 g/100 g found in the present study was much higher than the reported value of 6.88 g/100 g in the Indian Food Composition Tables (Copeland. Et al., 1989) indicating a general increase of protein content in Indian rice varieties. Factors such as environmenttall condition, soil fertility, fertilizer use and post-hervest processing can influence the protein content of rice; however, the present study examines only the varietal difference and not the other factors that can influence protein content in rice.
Brown rice ash content in 269 rice cultivars ranged from 0.9 g/100 g in Panted to 1.99 g/100 g in IR36 vanrite. Mean brown rice ash content was 1.38 g/100 g, comparable to brown rice from Brazil (1.21 g/100 g) and wild rice varieties from China (Heinemann et al., 2005; Zhao et al., 2001). Frequency distribution showed that 64 percent of the samples had ash content between 0.9 and 1.5 g/100 g, while 36 percent had ash content between 1.5 and 2.0 g/100 g reflectin mineral abundance in many rice varieties.
Correlations among the contents of ash and eight mineral elements in brown rice
Among the minerals, close positive correlation was observed betweed the contents of Zn and Fe, Cu and Fe or Zn, Me and Cu, Ca and Fe or Man, Mg and Fe or Zn or Cu, P and Fe or Man or Mg, K and Ca or Mg, while negative correlation was observed between the content of Ca and Zn, Mg and Ca, P and Zn. Jiang et al. (2007) also observed positive correlation between Fe and Zn saggusting that high iron content is accompanied by high zinc content in rice. There were differences in the corerelations among other elements between the Chinese rice genotypes and the present study which may be due to the fact that Jiang et al. (2007) used polished rice whereas brown rice was used in the present study. Significant positive correlation was observed between Mg and all other elements studied except Man. This may be explained by the fact that Mg ragalasted the uptake of all other essential elements and thus the Mg content of rice grain assume importance (Tucker, 1999).
Amino acid content and Amino acid score
Box plot showing distribution of various amino acids in 42 high yielding rice cultivars is shown in Figure 1. The total essential amino acids made up 39% of the total amino acids. Lysine content ranged from 3.42g/100g in AP 41 Kanchanalak to 4.2g/100g in AP 71 Pretax with a mean of 3.76 ± 0.20 g/100g protein. Shaker and Reddy (1982) has also reported wide varyaction in lysine content (2.82 to 4.86g/100g protein) in scented rice varieties. In contrast low lysine content (2.8g/100g protein) was observed in Mexican and Malaysian rice varieties (Roohinejad et al 2009; Stele et al, 1994). In the present study besides AP71 Prate another two varieties AP 85 Saale and AP106 also had lysine content above 4 g/100g protein. Wide geentice variability for lysine content in Indian rice varyreties has been reported (Bannered et al, 2011). The mean ± SD of heroine content, the second limiting amino acid in rice was 3.45 ± 0.21 g/100g protein. The lowest heroine content of 3.03 g/100g protein was observed in IR 64 while the highest content of 3.86 g/100g protein was found in AP 85 Saale.
Box plot showing the distribution of various fatty acids in 85 Indian rice cultivars is presented in Figure 2. The major fatty acids were politic (range 20 – 26%), oleic (range 30 – 37%) and linoleum acids (33 – 42%) which accounted for more than 92% of the total fatty acids. Studies on non-glutinous rice culltears from Japan also showed similar content of the major fatty acids politic, oleic and linoleum acids (Kite et al, 2005). The Mean ± SD content of muriatic , static and α-linolenic acids was 0.32 ± 0.06, 2.63 ± 0.50 and 1.52 ± 0.23 respectively. Α-lipolemic content ranged from low of 0.93 to as high as 2.19%. Caprice acid was detected at very low levyells ranging between 0.02 – 0.32 % in the present study. There is no report on the presence of Caprice acid in rice and this is the first report of the kind. A sample chromatogram of one rice fatty acid profile showing distinct peak of caprice acid is depicted in Figure 3.