Mild refining of triglyceride oil

Details Mild refining of triglyceride oil Mild refining of triglyceride oil

1998-03-02

2000-11-14

Carr, Deborah

Organic compounds -- part of the class 532-570 series

Organic compounds

Fatty compounds having an acid moiety which contains the...

554212, 426541, 426544, 426545, 426546, C11B 300

Patent

active

061472379

DESCRIPTION:

BRIEF SUMMARY
The present invention is concerned with a process for the refining of triglyceride oil under very mild conditions.


STATE OF THE ART

The purification process of a crude edible oil, particularly a triglyceride oil usually includes an initial removal of phospholipids (degumming), followed by the removal of substances which have a negative influence on taste, flavour and keepability. Those substances comprise inter alia free fatty acids, destabilising hydroperoxydes and, possibly, pesticides and polyaromatic hydrocarbons. Several unwanted substances may be removed by a process called deodorisation, which can be performed by gas stripping the oil with a stripping medium, usually steam or nitrogen, at temperatures above 200.degree. C. and at reduced pressure. At such relatively high temperatures stripping may cause modification of the oil so that other unwanted compounds may be formed. A further disadavantage is that consumers may perceive high temperature gas stripping as a non-natural process, while natural processes are preferred for the preparation of foodstuffs and foodstuff ingredients.
PCT application WO 94/12596 (UNILEVER) provides a method for refining a triglyceride oil which comprises acidifying the oil and removing substances which separate from the oil, followed by a heat treatment, which consists of keeping the oil several hours at an elevated temperature (simmering) and stripping the oil at a temperature of 30-200.degree. C. at reduced pressure. The compounds formed by oil oxidation will decompose during simmering and the volatile compounds formed are removed under reduced pressure conditions by the stripping gas. This method, because of the relatively mild conditions is referred to as mild refining and may be supported by a treatment with adsorbents.
Crude triglyceride oils contain hydroperoxides which are unstable substances resulting from oxidation of the oil. Unless a deodorization step removes this matter, off-flavour is readily formed during storage of the oil. The extent of oil oxidation and the content of hydroperoxides is expressed as a peroxide value (POV). The above prior art simmering process is carried out at a preferred temperature of 60-160.degree. C. In order to lower the POV from about 10 to <1 the oil needs 15 hours of heating at 120.degree. C. The process may proceed at still lower temperatures, temperatures which are perceived as relatively more natural, but a longer time would be required for obtaining a satisfactory result; 40-50 hours is common for temperatures below 100.degree. C. A deodorizing process which proceeds quickly at such low temperatures would fullfil the need for enhanced natural oil processing.


SUMMARY OF THE INVENTION

It has now been found that the time as well as the temperature needed for decomposition of hydroperoxides in triglyceride oil can be reduced considerably when the gas stripping treatment is preceded by exposure of the triglyceride oil to an aqueous solution of ascorbic acid.
It has been found that even at exposure temperatures below 100.degree. C. a satisfactory reduction of the POV is realised within several hours.


DETAILS OF THE INVENTION

The treatment of the triglyceride oil with ascorbic acid precedes stripping with an inert gas, preferably steam. It is important that the ascorbic acid is applied as an aqueous solution, which preferably contains about 20 wt. % of ascorbic acid and which suitably is dispersed into the oil. Vigorous stirring, using for example an effective stirring device such as the high speed Ultra-Turrax.TM., promotes a quick and complete reduction of POV, probably as an effect of the increased contact surface of the oil with the droplets of the ascorbic acid solution. The size of the droplets preferably is 0.1-100 .mu.m. The dispersed aqueous phase has an ascorbic acid concentration being 5-65 wt. %, preferably 15-50 wt. %. Calculated on the oil the concentration of ascorbic acid preferably is 0.01-1.0 wt. %, more preferably 0.05-0.15 wt. %.
The effect of the peroxyde decomposition is greatly enhanced when the

REFERENCES:
J. Agric. FoodChem., 1994, 42, pp. 1054-1059.
Fette, Seiffen, Anstrichmitel, vol. 85, No. 12, 1993, pp. 479-483.
ISO 3960: 1998 (E), "Determination of peroxide value in animal and vegetable oils and fats", pp. 1-7-mentioned on p. 5 of the specification.

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