Monday, September 22, 2014
Experts warns against exposing vegetable oils to sunlight
Vegetable oils which forms a good part of human diet providing concentrated sources of energy and essential nutrients is described to be losing its quality if displayed under direct sunlight in open markets, an expert on industrial food processing has said. A senior research and development officer of Tanzania Industrial Research Organisation (TIRDO) Sara Lifa said early this week in Dar es Salaam that, the exposure of vegetable oils to sunlight can result in the production of off-flavours, colour defects as well as loss of nutritional quality of the oils. She said in an exclusive interview that, in the process known as photo-oxidation, the essential fatty acids and rich vitamins E which are present in the oils are oxidized and their nutritive values reduced. However, she said “storage of vegetable oil under poor conditions will result in the loss of quality, and therefore the value of the product, and added that, it is therefore recommended that edible vegetable oils be stored in airtight containers that do not allow light and should not be exposed to sunlight. This blog contacted a vegetable oil expert with a view to get to know what could be the better resultant caused by such products after having discovered that, in some occasions locally produced vegetable oils are found displayed under direct sunlight in open markets which according to health regulations is strictly forbidden. Giving the technical details on the issue as prescribed in research papers, Sara noted that, when oils are exposed to sunlight their bond contents become photoxidized. In the process oxygen reacts with the double bonds of fatty acids to form peroxides. The rate of photo-oxidation is affected by some factors such as the presence of oxygen, intensity of radiation, degree of un-saturation and temperature. She noted that, one of the major changes taking place in vegetable oils is generally referred to rancidity. Rancidity is the state caused by the hydrolysis or oxidation of the glycerides and release of fatty acids which have strong characteristic and undesirable odours. There are two types of rancidity; hydrolytic and oxidative rancidity. In the oxidation type there are three categories: auto-oxidation, photo- oxidation and enzymatic oxidation. It is the photo-oxidation process which the initial stages are catalysed by light. Commenting on Sun-Flower oils she noted that, the oil is common cooking oil that has high levels of polyunsaturated. It is also known for having a clean taste and low levels of fat. It has a high in the essential vitamin E and low in saturated fat. Sunflower oil, like other oils, can retain moisture in the skin. It may also provide a protective barrier that resists infection in premature infants. Studies using sunflower oil have been conducted involving low birth weight infants who are often susceptible to infection due to their underdeveloped skin. Contacted for more comments, the Director of Quality Management Directorate of Tanzania Bureau of Standards (TBS) Eng. Tumaini Mtitu said that, a processor of any kind of cooking oil can technically ensure that processed cooking oils comply to requirements of a given standard by sourcing raw materials (oil seeds) that have been produced under Good Agricultural Practices (GAP). However, she noted that, ‘this should be followed by processors adhering to Good Manufacturing Practices (GMP) and Good Hygienic Practices (GHP). Therefore, during packaging of processed cooking oil the above need to be considered. She said in an exclusive interview that, the requirement is very important for all processors, whether Small, medium or large entrepreneur. During processing they should ensure that they adhere to GMP and GHP as these will assure them quality products on packaging. Producers of oil must ensure that packaging materials are those appropriate to packaging of oil. Use of plastic packages, glass and others that do not allow penetration of light (non-transparent) is the right measure to control exposure to light. On his part, the Director of Food Safety with the Tanzania Food and Drugs Authority (TFDA) Raymond Wigenge has said that, Tanzanians are at risk of being infected by diseases resulting from lack of enough nutrients such as vitamins and minerals in some foodstuffs which they consume. Among them he noted vegetable oils, bearing the fact that vitamins and mineral food components helps to protect human body against minor diseases. He confirmed in Dar es Salaam recently during an exclusive interview with this paper that, such foodstuffs are mixed up with insufficient contents of food nutrients during production with low percentage rate, and when consumed do not build up human bodies as required. The call by TFDA came about amid study reports conducted by Tanzania Food Centre (TFC) which revealed that in Tanzania there is a deficiency of some vitamins and other minerals on human bodies which has been discovered to be lacking in some foodstuffs including edible vegetable oils which are destroyed during the process of refining them. However, he noted that, with the escalating situation, his organization has seen the need of adding natural vitamins and minerals, and has embarked effectively on National Fortification Programme (NFP) whose aim is to minimize effects associated with micro-nutrient deficiency in the country. Elaborating on the initiatives and measures to be undertaken under the programme, he said both local and foreign food producers and sellers would be examined according to the newly introduced guidelines to start effectively end of this year. Under the new guidelines, TFDA will look at the imported foodstuffs such as Maize flour, Wheat flour and vegetable oils in order to verify their contents if they conform to the level of food standards required by TFDA. He said TFDA has issued a directive to food importers to inform their manufacturers and producers of such foodstuffs to strictly adhere to the new guidelines which his organization has issued as most of their consignments have been discovered to have a shortfall of the basic nutritious contents.