EVALUATION OF QUALITY OF FRESH SOYA-BEAN OIL AVAILABLE IN BANGLADESH

ABOUT AUTHORS:
MR. Zubair Khalid labu^*1, Md. Abdul Bake², Razia Sultana^3
1,3 Department of Pharmacy, World University of Bangladesh, Dhaka 1205, Bangladesh,
² Department of Pharmacy, Gono University, Savar, Dhaka 1344, Bangladesh.
* zubairlabu@yahoo.com

ABSTRACT
Hydrogenated soya-bean oil is the product obtained by refining, bleaching, hydrogenation and deodorisation of oil obtained from seeds ofGlycine soja Sieb. and Zucc. andGlycine max (L.) Merr. (G. hispida (Moench) Maxim.). Soya-bean oilis a vegetable oil extracted from the seeds of the soybean. It is plant based and less harmful saturated fats and offers nutrition and health related benefits.  The main objective of this work has been done for the evaluation and analyzing the quality of soya-bean oil available in local market. For the examination of soyabean oil six fresh samples of different sources were collected randomly from the market. British pharmacopoeia (BP) specifications were used for the determination of acid, peroxide and iodine value. The results were compared with the standard specified by Bangladesh standard and testing institute (BSTI). After three months study we observed that physical examination of all the samples were complies with the specification and chemical examination such as, In case of peroxide value, all the samples were found to comply with the specification and only two (S-5 and S-6) of them have comparatively higher value but remain within the limit. But In case of iodine value, five samples were within the limit, and only one sample (S-6) was out of specification. After over third month analysis we observed that all the sample value were higher than from first month study. The consumers which have to take this spurious product must be careful to take this because it may be harmful if adulterated.

REFERENCE ID: PHARMATUTOR-ART-1668

INTRODUCTION
Oil is a complex mixture of thousands of different compounds, composed primarily of carbon, hydrogen, sulfur, nitrogen and oxygen.  Hydrocarbons (composed solely from carbon and hydrogen atoms) are the most abundant compounds found in crude oils.

Soya-bean oil is a  white mass or powder which melts to a clear , pale yellow liquid when heated, practically insoluble in water, freely soluble in methylene chloride, in light petroleum (bp: 65°C to 70°C) after heating and in toluene, very slightly soluble in alcohol.

It is used as a raw material for the manufacture of cosmetics, printing inks, soaps and synthetic detergents, paints and varnishes, polishes, lubricants drying and pharmaceuticals.

At the present time the human race uses an estimated 40 million tons of fats and oils per year which reflect both their nutritional and industrial importance. From the chemical view, a fat or oil is a tri-glyceride which is the condensation product of one molecule of glycerol, with three molecules of fatty acids. Soybean oil, also known as ‘’Chinese Bean’’ is a widely used and versatile vegetable oil. Soyabean oil high smoke point makes it popular as frying oil, particularly in Asian Cuisine. 

Soyabean oil is plant based and less harmful saturated fats, it contains no cholesterol.  In addition to practical uses Soyabean oil offers nutrition and health related benefits. 

Extracted from Soyabean in this light yellowish oil is high in both polyunsaturated fats (58 percent) and monounsaturated fats (23 percent), and low in saturated fats (13 percent).  It is one of the most widely consumed cooking oils.  As a drying oil, processed soybean oil is also used as a base for printing inks (soy ink) and oil paints.  It is also converted to cooking oils.

It composed of saturated and unsaturated fats. 100 grams of Soya-bean oil has, 16 gm of saturated fat, 23 gm of mono-unsaturated fat, and 58 gm of poly-unsaturated fat. The major unsaturated fatty acids in soybean oil namely tri-glycerides are 7%-10% Alpha linolenic acid (C18:3); 51% linoleic acid (C-18:2); and 23% Oileic acid (C-18:1). It also contains the saturated fatty acid namely stearic acid 4%, palmitic acid 10%.

Soya-bean oil contains higher energy, fats. One cup of hydrogenated soya-bean oil contains energy 1925 calories, fat 218 gm and saturated fat 32.5 gm.

Fat Comparison Chart:
The following table shows, in grams, how much saturated, mono-unsaturated, poly-unsaturated and trans-fats are contained in 1 tablespoon of various commonly used oils and fats.

Table-1:  Fat Comparison Chart

Availability of Soya-bean Oil Materials in Bangladesh:
Soya-bean seeds contain about 20% of oil.  From regional trial, best location for soya-beans seem to be Ishurdi, Bakergong, Comilla, Noakhali, Dhaka, and Mymonshing. 

Actually, small quantities of soyabeans are growing in Bangladesh and it could not make significant increase in production in spite of the co-ordinated efforts of BARC (Bangladesh Agriculture Research Council) and UNICEF (United Nations International Children Emergency Fund).  At present crude degummed soya-bean oil is imported from the USA and processed further through neutralization, bleaching and deodorization.  70% of this marketed as refined edible vegetable oil with the remaining 30% further hydrogenated to produce vanaspati.

Materials
Fresh soybean oil, collected randomly from different shops.  This includes six samples which are collected from shop of open and closed container. The sample namely F-01, F-02, F-03, F-04, F-05, and F-06 coded as S-1, S-2, S-3, S-4, S-5, and S-6 respectively. The quantity for each sample collected was 500 ml. Reagents were used to carry on the determination of peroxide value Glacial acetic acid (Active Fine Chemicals, Bangladesh), Chloroform (Active Fine Chemicals, Bangladesh), Saturated potassium iodide solution (E-marck, Germany), 0.01M Sodium thiosulphate solution, 1% starch solution as indicator; for the determination of acid value, Ethanol (95%) (Active Fine Chemicals, Bangladesh), Ether, 0.1M potassium hydroxide solution, Phenolphthalein solution (indicator), Potassium Hydrogen Phthalate solution for standardization and 0.1 mol/L sodium thiosulphate, Carbon tetrachloride, Henus solution, 15% potassium iodide solution were used for the determination of iodine value of the collected samples.

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Methods
Titrimetric method is used for the determination of peroxide, iodine, and acid value of the samples. 

For the determination of peroxide value following steps are followed:

1. 5 gm. of sample was taken in a 250 ml glass stoppered conical flask then 30 ml of a mixture of 30 volumes of glacial acetic acid and 20 volumes of chloroform was added and shaken until the sample was dissolved.

2. Then 0.5 ml of saturated potassium iodide solution was added and shaken for exactly 1 minute and then we added 30 ml of water.

3. Then titration was done slowly, and shaken continuously with 0.01M sodium thiosulphate VS until the yellow color almost disappeared.

4. Also 5 ml of 1% starch solution was added and continued the titration, shaking vigorously, until the blue color just disappeared.

5. The operation was repeated without the substance being examined and this served blank.  The titration in blank determination should not exceed 0.1 ml of the sodium thiosulphate solution.

For the determination of acid value following steps is followed:

1. 10 gm. Of the sample being examined was taken and dissolved it in 50 ml of a mixture of  volumes of ethanol (96%) and ether that has been neutralized with 0.1M potassium hydroxide  VS  Using 0.5 ml of dilute phenolphthalein solution as indicator.
2. Then the standardization of KOH solution (0.1M) was done with 0.1M of potassium hydrogen phthalate.
3. Titration was done with 0.1M potassium hydroxide VS shaking constantly, until a pink color that persisted at least for 15 to 30 seconds.

For the determination of iodine value following steps is followed:
1. 0.1 gm of sample was delivered to a 300 ml conical flask with ground in stopper.  Then 20 ml carbon tetrachloride was added and sealed and dissolved in an ultrasonic washing machine.
2. Further 25 ml Hanus solution was added and sealed.   Shake for a minute.
3. Then it was sealed and leaved it in a dark room (about 20oC) for 30 minutes.
4. 10 ml of 15% potassium iodide and 100 ml water were added and sealed.  And shake for 30 seconds.
5. Titration of it with 0.1ml/L sodium thiosulphate was done to obtain iodine value.
6. Likewise blank test was performed to obtain blank level.

RESULTS
From the table-2, In the month of October, physical observation namely color, clarity, odor, sedimentation and chemical analysis namely peroxide, iodine, acid value of different sample was complies with the specification. But in S-6, iodine value was higher (165.30) than the normal range. In the second months study physical observation of the different samples slightly change from the previous months but it may be considered as complies with the BSTI specification. In the month of November, physical characteristics of all samples was complies with the standard and chemical analysis of peroxide, acid, iodine value of S-1, S-2, S-3, & S-4 was complies according to specification but only iodine value of S-5 (145.65) and S-6 (168.78) was out of specification. In the month of December, only iodine value of S-4 (144.04), S-5 (147.06) and S-6 (170.66) was out of specification.

Table – 2:  Peroxide value, Acid value, Iodine value of different samples.

DISCUSSION
Peroxide value indicates the presence of miff of oxygen per kg of anhydrous oil.  Higher peroxide value also indicates the rancidity of oil and the presence of higher amount of free radicals at the same time.  Actually peroxide value increases due to the auto-oxidation.  Free radical reactions are chain reaction and are ubiquitous in living beings.  As radicals are highly reactive they are capable of randomly damaging all components of the body.  These are involved in the development of chronic disease like cancer, atherosclerosis, and emphysema. According to BP specification the normal limit of peroxide is 5.0. In S-5, October, November, and December result was 0.0096, 0.105, and 0.112 respectively. In the month of November and December the result was high value compared to the month of October due to environment exposure, various contaminations occur in storage. In S-6 has also higher value compared to previous samples but contain it within the limit.

Acid value is the measurement of the presence of free fatty acids in the sample which are normally formed due to hydrolysis of the lipid.  The acid value of oil is used as a measure of quality.  The acid value of the oil must not be  too high, as this denotes an excessively high  content  of free fatty acids [FFA], FFA can be determined from the acid value.  High FFA, affect the yield of the biodiesel.  This is in accordance with literature.  The acid value of the vegetable oil should be less than one for a base [KOH] catalyzed Trans-esterification process.  The causes of high acid value may be due to improper processing or distillation, presence of micro-organisms, improper storage, exposed to light etc.  Temperature has a very important effect on the increases in acid value. It appeared from the table-3, that all the six collected samples had the acid value within the BSTI specification [Max. 0.6].Fats and Oils with higher acid value can result in gastric acidity, gastric discomfort, maldigestion and these also lose the consumer’s acceptability due to odd color and odor. The acid value of all the samples was within the specifications in different months.

The iodine value [IV] is a measurement of the unsaturation of fats and oils.  High iodine value indicates high unsaturation of fats and oils [Knothe, 2002, Kyriakidis and Katsiloulis, 2000].  Among the six fresh soybean oil [Table-11] only five were found to comply with the BSTI specification [120-143] and the rest had the higher value.  So, the degree of the sample was high and could be considered as substandard to respect of iodine value. Sample number 5 was the higher value in November (145.65) and December (147.06) and sample number 6 (S-6) has more value (October-165.30), (November-168.78), (December-170.66) than the other samples. So, we consider it as a substandard sample.

CONCLUSION
The manufacturing technology of Soyabean Oil is sample and so many brands are available in the market.  But some immoral manufactures and salesman intentionally mix up various adulterants which are found to be quite by cheap.  The consumers which have to take this spurious product are the most loser and these may be life threatening because adulterants may also be toxic product.

The Government of the Peoples’ Republic of Bangladesh on 25^th July, 1985 had published.  The Bangladesh Standard and Testing Institute Ordinance 1985 to provide for the establishment of an institution, for standardization, quality control, grading and marking of consumer goods.  In the Bangladesh Standard and Testing Institute Ordinance, 1985, it is mentioned that whoever use improper standard mark manufactures and sale any substandard consumer product shall be punished with imprisonment for a term which may extend six month or with fine which may extend to 15,000.00 taka or with both as well as whoever contravenes any of the provision of this ordinance shall be punishable with fine which may extend to five thousand taka.  Unfortunately the people of Bangladesh do not see the application of this law while substandard brand are there in the market.

Unintentionally, the soyabean oils may be substandard due to improper processing, storage, and lack of maintaining good quality control practice.  From the analytical results, it is seen that the analytical result of few brand are very near to the standard value if they do maintain quality control properly they would definitely confirm Bangladesh Standard and Testing Institution (BSTI) Standard. 

Thus, to ensure quality of fresh soyabean oil, many BSTI branch should be set up in different region of Bangladesh and analysis should be continued.  Introducing sample method to detect adulterant may play an important role.

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