J. V. Prabhakar

A simple chemical method for stabilization of rice bran.

A new simple chemical method for stabilization of rice bran is described. The process, based on the principle that lipase activity will be low at low pH, uses hydrochloric acid at 40 l/ton of bran for lowering the pH of rice bran from 6.9–6.0 to 4.0. The acid can be applied easily by sprinkling or spraying. The operation on small lots can be done by hand mixing of bran, but it is more efficient and effective if mechanical mixing, like a rotary or a trough mixer, is used. This simple method, which takes less than 4 min for a batch of 15 kg, will be useful for stabilization of rice bran in rice mills or where steam or electricity is unavailable. The process is being evaluated in commercial trials.

Lipid composition of rice (Oryza sativa L.) bran

The composition of lipids of bran from three varieties of rice is reported. Lipids extracted amounted to 21.9–23.0% of the bran dry weight and consisted of 88.1–89.2% neutral lipids, 6.3–7.0% glycolipids and 4.5–4.9% phospholipids. Neutral lipids consisted mostly of triacylglycerols (83.0–85.5%), monoacylglycerols (5.9–6.8%) and small amounts of diacylglycerols, sterols and free fatty acids. Three glycolipids and eight phospholipids were separated and characterized. Acylated steryl glucoside and digalactosyldiacylglycerol were the main glycolipids, while monogalactosylmonoacylglycerol was present in small amounts. The major phospholipids were phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidic acid. Phosphatidylglycerol, lysophosphatidylcholine, lysophosphatidylethanolamine and acyl-phosphatidylethanolamine were present in small quantities.

Cocoa butter extenders from Kokum (Garcinia indica) and Phulwara (Madhuca butyracea) butter

Cocoa butter extenders, suitable for use in chocolate and confectionery, were prepared from Kokum fat and a Phulwara butter fraction. The latter fraction was prepared from Phulwara butter by two-stage dry fractionation and blended with Kokum fat in selected proportions to obtain a series of hard butters with different melting profiles. The blends with higher proportions of Kokum fat were harder and hence may find application in warm climates. The blends with higher proportions of Kokum fat were harder and hence may find application in warm climates. The blends had solidification properties, fatty acid and triacylglycerol compositions similar to those of cocoa butter. In addition, they had narrow melting ranges like cocoa butter, and they were compatible with cocoa butter and have tolerance toward milk fat.

Lipid composition of fenugreek (Trigonella foenumgraecum L.) seeds

Abstract Total lipids extracted from fenugreek ( Trigonella foenum-graecum L., Leguminosae) seeds amounted to 7·5% of the dry seeds. The total lipids consisted of 84·1% neutral lipids, 5·4% glycolipids and 10·5% phospholipids. Neutral lipids consisted mostly of triacylglycerols (86%), diacylglycerols (6·3%) and small quantities of monoacylglycerols, free fatty acids and sterols. At least five glycolipids and seven phospholipids were identified. Acylmonogalactosyldiacylglycerol and acylatedsterylglycoside were the major glycolipids, while sterylglucoside, monogalactosylmonoacylglycerol and digalactosyldiacylglycerol were present in small amounts. The phospholipids consisted of phosphatidylcholine, and phosphatidylethanolamine as major phospholipids and phosphatidylserine, lysophosphatidylcholine, phosphatidylinositol, phosphatidylglycerol, and phosphatidic acid as minor phospholipids. The fatty acid composition of these different neutral lipids, glycolipids and phospholipids was determined.

Effect of triglycerides containing 9,10-dihydroxystearic acid on the solidification properties of sal (Shorea robusta) fat

Components affecting solidification properties of sal (Shorea robusta) fat have been studied. Triglycerides containing 9,10-dihydroxystearic acid (DHS-TGs) present to about 3% have been found to affect the supercooling property of sal fat at as low a level as 2%. The DHS-TGs were composed of 57.5% stearic, 5.8% arachidic, 6% palmitic and 30.5% 9,10-dihydroxystearic acids. As DHS-TGs are soluble in acetone, solvent fractionation using acetone improved the supercooling capacity of stearin while that of the olein fraction was not affected. When the fat was subjected to dry fractionation at 35 C, DHS-TGs, due to their high melting nature, were removed to a greater extent in the form of stearin, thereby improving the supercooling capacity of the olein.

Factors affecting refining losses in rice (Oryza sativa L.) bran oil.

Components of rice bran oil have been assessed for their effect on refining losses. Rice bran oil used in the study had the following (percent) analysis: free fatty acids, 6.8; phosphatides, 1.25; wax, 2.85; monoglycerides, 1.67; diglycerides, 4.84, and oryzanol, 1.85; the rest (80.74) was mostly triglycerides. The phosphatides and mono- and diglycerides had no noticeable effect on refining losses at levels of up to 2% in the oil. Waxes and oryzanol increased the refining losses substantially. In model experiments where these were incorporated into peanut oil individually and in combination, the wax at as low a level as 1% increased the refining losses by about 80% more than control and the refining losses increased with concentration of wax. Oryzanol had a similar effect. When wax and oryzanol were present together in the oil, the effect was synergistic—the refining losses were higher than the sum of their individual effects. Phosphatides, mono- and diglycerides tended to reduce the adverse effect of wax and oryzanol. The main components responsible for higher than normal refining losses in rice bran oil have been identified as wax and oryzanol.

Study on the polymorphism of normal triglycerides of sal(Shorea robusta) fat by DSC. I. Effect of diglycerides

The effect of diglycerides (DG) on the phase transition of various polymorphic forms of normal triglycerides (TG) of sal fat was investigated by differential scanning calorimetry. Three levels of DG, 5, 10 and 15%, were used. DG delayed the phase transition of lower melting crystal forms to higher forms of TG when the samples were brought to a congealed state by rapid cooling (20 C/min) and heated at rates ranging from 1.25 to 10 C/min; the extent depended on the level of DG and the rate of heating. As the level of DG and the rate of heating increased, the delay in phase transition of crystal forms I → II → III was more pronounced. The phase transition of crystal forms I, II and III to form IV was delayed at 5 and 10% levels of DG, while at the 15% level the phase transition of form I to higher forms was completely stopped when the samples were tempered at 0 C for 18 hr and heated at 10 C/min. DG at 10 and 15% levels retarded the phase transition of form IV to the most stable (V) form of TG when the samples were tempered at 0 C for 1 hr followed by 3 hr at 26 C.

Isolation of 9,10-Dihydroxystearic acid from sal (Shorea robusta) fat

Abstract9,10-Dihydroxystearic acid and its triglycerides (DHS-TGs) were isolated from sal fat by silica gel adsorption and solvent and dry fractionation processes, followed by crystallization. Silica gel adsorption gave a higher yield of DHS-TGs than the other two fractionation processes. However, the dry fractionation process was found to be comparatively easy to carry out. 9,10-Dihydroxystearic acid was isolated and identified by TLC, GLC, M.P. and IR-spectrometry. The DHS-TGs were found to contain 30.5% 9,10-dyhydroxystearic, 57.5% stearic, 6.0% palmitic and 5.8% arachidic acids. These processes were found to be useful for recovery of DHS-TGs and also to improve the solidification properties of sal fat required for confectionery.

Effect of water activity on autoxidation of raw peanut oil.

The effect of water activity (aw) on rate of autoxidation of raw peanut oil at 37 C was studied. Up to 3 weeks of storage, no marked effect of aw on the rate of peroxide formation was noticeable. However, with prolonged storage, the rate of peroxide formation decreased rapidly at aw of 0.67 and higher as compared to aw of 0.50 and lower. At the end of 9 weeks’ storage, the peroxide value at aw=0.02-0.50 was in the range of 31–35, while it was only ca. 10 at 0.79 and 0.92 aw. There was no noticeable influence of aw on the rate of free fatty acid formation. The oil stored for 7 weeks at 0.02 and 0.11 aw had fresh flavor, although the peroxide values were high; whereas the oils at 0.79 and 0.92 aw were stale, although the peroxide values were less than 10. The anisidine value at 0.02 aw (348) was higher than at 0.92 aw (62). The carbonyl values at 0.02 and 0.11 aw were also higher (1090, 1021) than at 0.79 and 0.92 aw (573, 780). The results indicate that the protective effect on the oil against peroxide formation at high aw may be due to certain components present in raw peanut oil.

Effect of water activity on secondary products formation in autoxidizing methyl linoleate

The role of water activity on the formation of peroxides and carbonyl compounds during lipid oxidation is important to know because there could be either beneficial or detrimental effects of water activity on lipid oxidation in stored foods. Therefore, methyl linoleate was chosen as a model lipid and was autoxidized to 1% at water activity ranging from 0.02 to 0.79 at 37°C. Oxygen uptake was monitored manometrically. The peroxide and carbonyl contents were determined upon termination of the autoxidation studies. Methyl linoleate autoxidation was characterized by three phases: i) an initial induction period of no oxygen absorption; ii) a slow rate of oxygen absorption, up to 0.15% oxidation; and iii) a relatively faster rate of oxygen absorption beyond 0.15% up to 1% oxidation. Water activity had considerable influence during the first phase. There was no induction period at or below water activity 0.22. The induction period begins at water activity 0.32 and could be extended to a limit with increase in water activity. Once the induction period was passed water activity had no influence on the rate of oxidation. However, during the second and third phases water activity becomes important in the stabilization of peroxides/hydroperoxides and decides the course of secondary reactions that follow peroxide decomposition. Higher water activity values, particularly water activity 0.67, tended to stabilize peroxides. Water activity had considerable influence on the formation of secondary products of autoxidation as evidenced by the variation in the type and quantity of carbonyl compounds at different water activity values.