High-Stability Non-Lauric Triglyceride Oils

A frying oil having a high heat stability is known from JP 2 214 799-A. According to this Japanese document, the oil has a low increase in acid value and a low degradation in colour and taste when heated.

The oil is obtained by purifying crude palm oil to provide purified palm oil, fractionating the oil and treating the intermediate fraction with alkali. The IV of the intermediate fraction is 29-46. The treatment with alkali (2-20% NaOH in amounts of 1-5 wt.% at 40-95.degree. C.) is followed by a water wash and a filtering step (activated clay) and finally by a steam deodorization.

Although the properties of this product are acceptable, it does not meet the very high standards for a high-stability oil (=HSO). An HSO should display a RIP (=Rancimat Induction Period) of at least 35 hours (at 120.degree. C.), measured according to the method described in Fette, Seifen und Anstrichmittel, 88, Nr. 2, 1986, pp. 53-56.

Although triglyceride compositions (e.g. Durkex-500.RTM., cf. US Pat. No. 4,748,041) are known that display RIP values of about 35 hours (at 120.degree. C.) (i.e. AOM values of about 350, cf. column 4, lines 5-6), these triglycerides still contain appreciable amounts of solids at ambient temperatures (N.sub.1O = 20, N.sub.20 <10). The iodine value of these oils is at most 81. These triglycerides therefore have the disadvantage that they are not pumpable and/or sprayable at ambient temperatures. Moreover, the colour and colour stability of these oils are not optimal.

A fraction of Durkex-500 (=Durkex-HSO.RTM.) is also mentioned in this patent. This fraction has an I.V. of 80; however, an emulsifier needs to be added in order to make a filtered product cloudless at 10.degree. C. (cf. column 5, lines 1-18).

From JP-55 069 696-A another highly stable fat is known that can be used for frying and spraying. This product is obtained from hardened palm oil. The fat has a high content of trans-acids and displays an AOM value of more than 200 (so, RIP of about 20-25). It is not clear what the solid fat indexes of this fat are at ambient temperature, but, considering the high amounts of trans-acids, they are expected to be rather high.

From GB 867,615 improved soft oils (see page 8) are known that display AOM values of at least 200 hours. According to the Table on page, a maximum AOM of 288 hours can be achieved, which is too low for a high-quality HSO. The reason for such an AOM value is probably that too high amounts of C.sub.18:2 are present in the oils.

We have now found new high-stability oils that combine an excellent RIP stability with an excellent colour stability. In addition, the oils are essentially liquid at ambient temperatures.

Therefore, the invention concerns in the first place a high-stability oil (HSO) comprising a vegetable, non-lauric triglyceride composition with a maximum amount of C.sub.18:3 fatty acids of 1 wt.%, preferably less than 0.5, and particularly preferably less than 0.05 wt. %, a maximum amount of C.sub.18:2 fatty acids of 10 wt. %, preferably less than 8 wt.% and particularly preferably less than 5 wt.%, while the oil contains very small amounts of Fe, Cu and Ni, in particular not more than 0.2 ppm, and more preferably less than 0.1 ppm Fe, not more than 0.04 ppm, and more preferably less than 0.02 ppm Cu and not more than 0.2 ppm, and more preferably less than 0.1 ppm Ni; in the oil some amounts of natural tocopherols, in general at least 500 ppm, preferably at least 1000 ppm, are present. The HSO is liquid above 10.degree. C. having a solids line (NMR, not stabilized) of N.sub.15 <10, N.sub.10 <15, preferably <5.0 and N.sub.O <20, preferably <15.0 and in particular N.sub.10 <0.5 and N.sub.O <5. These oils display RIP values at 120.degree. C. of at least 35 hours, preferably at least 40 hours, and have iodine values (I.V.) of at least 81, preferably 82-95.

The oils are very colour- and taste-stable. The colour change of the oils during storage at room temperature for 12 months is typically less than 0.1 Red in lov. 51/4" cell, whereas the taste typically remains unchanged even after storage at room temperature for 6 months.

The oils can be obtained as the olein fraction of either a wet fractionation or a dry fractionation process, followed by standard refining.

An oil having very good properties is obtained when a hardened mixture of soybean oil and cottonseed oil (weight ratios of both at least 1.0 and less than 1.0 are applicable) is fractionated, preferably wet-fractionated. The olein fraction is recovered and is subjected to a dry fractionation or a wet fractionation. After refining, using conventional methods, the olein fraction of this last-mentioned fractionation is an HSO having the properties defined above.

Other examples of suitable HSO's are the refined olein fractions of the fractionation of hardened soybean oil, hardened rapeseed oil or mixtures thereof.

In fact, more olein fractions of the fractionation of hardened vegetable oils or mixtures of vegetable oils are useful as long as they meet the requirements of the HSO as defined above.

One of the main advantages of the invention is that, during the wet or dry fractionation, the natural antioxidants, in particular the tocopherols, are concentrated in the olein fraction so that no addition of synthetic or isolated natural antioxidants is necessary. This is particularly the case in wet fractionation. We therefore prefer to use this fractionation method. However, addition of an extra amount of antioxidants, such as tocopherols, e.g. up to 1500 ppm, can have advantages, in particular when very high RIP values are required.

The oils according to the invention can be used for many purposes. As a result, use can be made of the advantageous properties of the HSO's, i.e. their moisture-barrier characteristics, their lubricating and anti-sticking properties. The main advantage of the use of these oils is that they can be pumped to and/or sprayed by the nozzles of an apparatus without the need to heat the oil. In this way, the oils can be used for coating or enrobing of food products, like raisins, for dipping of food products, in tumblers, wherein the food is tumbled in the presence of a sprayed oil, for pan-coating of moulds for food processing, etc. The oils can also be applied to the surface of foods, such as dehydrated foods, breakfast cereals, dry soups, protein concentrates or hydrolysates, meats, frozen foods, pastries, pies, biscuits, snacks, confectioneries or mixtures thereof to reduce sticking or the transmission of moisture into or out of these foods.

Other applications of the oils are: a solvent for food flavours or colours, or as release agent for the surface of equipment for food purposes.

The invention will now be illustrated by the following nonlimiting Examples.

Soybean oil was hardened to a melting point of 32.degree. C. The hardened soybean oil of 32.degree. C. was wet-fractionated with acetone (ratio: 6 1 acetone per kg oil). The fractionation was performed at -3.degree. C. After separation of the stearin fraction and removal of the acetone, a liquid olein fraction was obtained in a yield of 60%, displaying the following characteristics (after standard refining) :

This product was used with excellent results for spraying on to raisins at ambient temperature.

To the product of Example I, an additional amount of 1430 ppm of tocopherols was added. The RIP (120.degree. C.) of this product was 41.6 hours.

A mixture of 50% soybean oil and 50% cottonseed oil was hardened (melting point 38.degree. C.). The hardened mixture was wet-fractionated (acetone ratio 5 1/kg; T=0.degree. C.).

A stearin fraction was separated from a solvent fraction (I). The solvent fraction (I) was cooled again, this time to -10.degree. C. A new solid fraction was removed from a second solvent fraction. Evaporation of the solvent, followed by standard refining, led to an olein fraction yield 53%, with the following characteristics:

The refined olein fraction of a wet fractionation of a hardened mixture of soybean oil and cottonseed oil (50:50) was dry-fractionated at 10.degree. C. An olein fraction yield 55% was obtained that displayed the following characteristics:

A wet fractionation with acetone at -10.degree. C. led to a similar result.

Example IV was repeated, but now the refined olein fraction of a wet fractionation of a hardened mixture of 30% soybean oil and 70% cottonseed oil was used. The product yield 60% displayed the following characteristics: