I

Cmde Soybean Oil

Waste Bleaching Clay <-BLEACHING 4-Bleached Clay

Denotes etminate processing.

Refined Bleached Deodorized Oil Salad 01

Refined Bleached Deodorized Oil Salad 01

Figure 5. Comparison between a classical process and a UF process for refining of edible oil b) Classical process (Reproduced with the permission from Reference [32]).

In general, vegetable oils for edible use, such as soybean oil or rapeseed oil, are purified and produced by a chemical refining process including hexane extraction and stripping, degumming, deacidification, washing, bleaching and deodorization. Chemical refining has disadvantages. Large amounts of energy are used in heating and cooling oil between process steps and in generating the required vacuum levels during the various process steps: chemical damage occurs due to severe treatment with alkaline solutions, resulting in considerable loss of oil. Also, chemical processing with water and chemicals results in large volumes of highly contaminated waste water. By degumming crude micella by ultrafiltration, and by removing hexane from the permeated micell ay a degummed oil can be obtained in one step, replacing the traditional degumming and deacidification steps and perhaps also replacing the bleaching step, as shown in Figure 5 [32], Potential applications are e.g., the recovery of phospholipids from oil-hexane and oil-IPA micella; removal of catalyst from hydrogenated oils and rejuvenation of used frying oils [33],

3.5. Waste water processing

It is of interest to treat waste streams from the food industry by membrane separation technology, partly for environmental reasons, and partly for the recovery of valuable substances and the reduction of water consumption. Examples of such applications are the treatment of different rinse waters, i.e., diluted products obtained when changing to another product or before cleaning and the treatment of cleaning solutions to recover alkali etc. By recovering proteins from effluents, e.g., potato fruit juice and red meat abattoirs, the product value can be increased. The environmental problems caused by olive oil production are substantial in most of the Mediterranean countries. The waste water contains large amounts of suspended and dissolved compounds, such as sugars, nitrogenous compounds, fats, acids, polyalcohols, polyphenols, pectins, and salts. The polyphenols can cause a reduction in the protein bio-availability when used as animal feed; on the other hand the recovery of polyphenols could give economical benefits if recovered and used as natural antioxidants and pigments. An integrated process for the treatment of effluents from olive oilmills was developed in a project supported by the European Community [34], The process includes a physical-chemical pre-treatment, UF and RO stages and a final polishing phase. It was found to be possible to recover polyphenolic substances with good antioxidizing properties from the waste water. The dephenolized residue could be used as an animal feed.

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