Stability of Vitamin a (retinol) in Fats/oils

The quality of locally available Ghee and oils was investigated at the department of Agricultural Chemistry, NWFP Agricultural University, Peshawar, Pakistan during May – October, 2005. Different brands of Ghee i.e. Shama Banaspati, Gulab Banaspati, Kohinoor Banaspati and Fauji Banaspati and Oil (Handi Cooking Oil) were analyzed for vitamin A contents and quality parameters (acid and iodine values). Analysis of data revealed that Handi Cooking Oil had maximum content of vitamin A (156.5 μg.kg) followed by Gulab Banaspati Ghee (91.4 μg.kg). The lowest vitamin A content was found in Shama Banaspati (73.8 μg.kg). Mean values of the data indicated that the acid and iodine values were in the range of 0.9 to 2.7 mg.g and 5.3 to 11.2 g.100 g, respectively. On exposure to ambient condition (for 7 days at 25-38 °C and 38-51 % humidity under incandescent bulb), the maximum degradation of retinol level was found in Handi Cooking Oil. Analytical analysis of free fatty acid and iodine value indicated that the exposure affected the quality of ghee especially of Fauji Banaspati, which might be due to the short chain fatty acid and unsaturation. INTRODUCTION Vitamin A (chemically known as retinol) was the first fat-soluble vitamin to be recognized in 1913. In nature it is found largely as an ester, and consequently is highly soluble in organic solvents but not in aqueous solutions. The major pro-vitamin, beta-carotene, has similar solvents properties. One of the richest sources of vitamin A is liver tissue. Vitamin A plays an important role in vision, bone growth, reproduction, cell division and cell differentiation (Smith and Steinmann, 2000). Its deficiency is usually caused by prolonged dietary deprivation. It is endemic in areas, such as southern and eastern Asia, where rice, devoid of carotene, is the staple diet. Other causes of deficiency include inadequate conversion of carotene to vitamin A or an interference with absorption, storage, or transport of vitamin A. For children, lack of vitamin A causes severe visual impairments and blindness, and significantly increases the risk of severe illness, and even death, from such common childhood infections as diarrhea disease and measles (West et al. 2001). For pregnant women in high-risk areas, vitamin A deficiency occurs especially during the last trimester when demand by both the unborn child and the mother is highest. The mother’s deficiency is demonstrated by high prevalence of night blindness during this period. Vitamin A deficiency may also be associated with elevated mother-to-child HIV transmission (Cox, 1999). As the fats and oils are good carriers of vitamin A out side and inside the body, so the fortification of oil/fats are taking place in many developed and under developed countries. Moreover, ghee or cooking oils are commonly used in daily diets; therefore it is an important way to fulfill the daily requirements of vitamin A. Since ghee or oils are exposed to air and humidity during various occasions of their processing and usage, so there quality may be disrupted. The air, water and temperature are main causes for vitamin A deterioration. A regular check is indispensable for quality control and to estimate the retention time of vitamin A. This study was designed to investigate the retention time and fat quality parameter (acid value and iodine value). MATERIALS AND METHODS Sample Collection A number of different brands of fats and oils (Shama Banaspati, Gulab Banaspati, Kohinoor Banaspati, Fauji Banaspati and Handi Cooking Oil), packed in polythene bags, were collected from different areas of Peshawar. The analysis was carried out at the laboratory of Agricultural Chemistry department, NWFP Agricultural University Peshawar, Pakistan during May-October, 2005. A small portion of them (termed as packed samples) was taken for analysis. The remaining portion of these fats and oils was kept exposed for 7 days at room temperature (25-38 °C and 38-51% humidity) under incandescent bulb. These samples (termed as unpacked samples) were analyzed in the same way as the packed samples to determine the difference. Determination of Vitamin A Vitamin A (retinol) contents were determined by colorimetric method (AOAC, 1984). Vitamin A content was expressed as μg.kg ֿ1. Calculation of Acid and iodine Values Acid and iodine values are the main parameters used for the quality measurement of fats. These values were determined according to the methods given in * Department of Agricultural Chemistry, NWFP Agricultural University, Peshawar – Pakistan. ** Department of Human Nutrition, NWFP Agricultural University, Peshawar – Pakistan. Sarhad Journal Agricultural. Vol. 23, No. 22007 456 A.O.A.C. (1984). The acid and iodine values can be calculated by the following formulas. Acid value (mg g) = T x N x 56.1 / wt of sample (T = titration reading in ml, N = normality of the alkali) Iodine Value (g 100g) = (B – S) x N x 12.7 / wt of sample (B = blank titration reading in ml, S = sample titration reading in ml, N = normality of Na2S2O3). RESULTS AND DISCUSSION The analysis was conducted in the laboratory of Agricultural Chemistry Department, NWFP Agricultural University, Peshawar. The data of acid value, iodine value and vitamin A content are presented in Tables I, II and III, respectively. In the data regarding the acid value, a significant difference was observed among the packed and exposed ghee and oils. The difference was also present among different brands. The acid value of Handi cooking oil was lowest (0.9 mg.g) among the packed samples followed by Shama Banaspati (1.0 mg.g), Kohinoor Banaspati (1.4 mg.g) and Gulab Banaspati (2.3 mg.g). The highest acid value was observed in Fauji Banaspati (2.7 mg.g). The maximum difference due to exposure was observed in Fauji Banaspati (2.4 mg.g). This might be due to unsaturation in the Fauji Banaspati. The result was in good agreement with that of Runge and Heger, (2000), who reported the effect of air on the acid value of different ghee brands. The iodine value of the subject Ghee and Oil was minimum in Gulab Banaspati (5.3 g.100g) and maximum in Handi cooking oil (11.2 g.100g). The reason was that the cooking oil contains more unsaturation and so they absorbed more iodine. The data agreed with the result of Langewar and Badole (2000). This result was also in line with Rathanam and Sail (1998) who reported that the partial unsaturation of ghee is due to the incomplete hydrogenation of ghee. The maximum decrease in iodine value was observed in Fauji Banaspati (3.6 g.100g). The iodine values decreased as the ghee exposed to the air because the oxygen in the air attack on the double bond and make their oxides. This causes the break down of fatty acids into short chain fatty acids like butyric acid which result in the bad smell of the ghee commonly known as rancidity (Rathanam and Sail, 1998). Vitamin A content among different brands was in the range of 73.8 to 156.5 μg kg. The minimum content was found in Shama Banaspati and maximum was present in Handi cooking oil. Similar result was reported by Dutra-de-Oliveira et al. (1998). The exposure affected the cooking oil worse and the difference was 47.9 μg.kg. The decrease in vitamin A content may be due to the more reactive attack of air oxygen or water. Table I Acid value (mg.gֿ1) of different commercial brands of Ghee and cooking oil (Packed and unpacked) Different brands of ghee and cooking oil* Reading A B C D E R1 1.0 2.0 1.7 3.0 0.5 R2 0.7 3.0 1.2 2.7 0.9 R3 1.2 2.0 1.3 2.3 1.2 Packed Mean 1.0 2.3 1.4 2.7 0.9 R1 1.7 4.3 3.1 4.9 2.8 R2 1.4 4.4 2.8 5.3 3.0 R3 1.4 4.2 3.1 5.1 3.2 Unpacked Mean 1.5 4.3 3.0 5.1 3.0 Difference 0.5 2.0 1.6 2.4 2.1 Table II Iodine value (g.100g־1) of different commercial brands of Ghee and cooking oil (Packed and unpacked) Different brands of ghee and cooking oil* Reading A B C D E R1 5.0 4.0 5.0 6.0 11.0 R2 8.0 5.0 7.0 9.0 10.5 R3 7.0 7.0 9.0 11 12.0 Packed Mean 6.7 5.3 7.0 8.7 11.2 R1 3.4 4.0 4.0 5.4 8.4 R2 3.6 4.2 4.3 5.0 8.6 R3 3.5 4.1 4.3 4.9 8.5 Unpacked Mean 3.5 4.1 4.2 5.1 8.5 Difference 3.2 1.2 2.8 3.6 2.7 (A = Shama Banaspati, B = Gulab Banaspati, C = Kohinoor Banaspati, D = Fauji Banaspati, E = Handi cooking oil) Sarhad J. Agric. Vol. 23, No. 2, 2007 457 Table III Vitamin A content (μg.kgֿ1) of different commercial fortified brands of Ghee and cooking oil (Packed