Vegetable and essential oils and fats which contain or consist of unsaturated organic compounds, are preserved against deterioration by oxidation by incorporating in the material moderately roasted cocoa bean or moderately roasted cocoa bean shell so as to enable the material to absorb anti-oxidants therefrom. Alternatively, an anti-oxidant containing extract is obtained from the moderately roasted bean or shell by an evaporable solvent, e.g. water at 60-90 DEG C., the extract being incorporated, with or without concentration, in the material. A preliminary de-fatting extraction of the bean or shell with petroleum ether or carbon tetrachloride is desirable. In the treatment of an oil or fat: it is heated to 60 DEG C. with 2 to 10 per cent of moderately roasted bean or shell which is afterwards removed by filtration and re-used. In the case of a partially hydrogenated edible fat, the addition of 5 per cent by weight, of defatted, ground, moderately roasted shell, and a heating treatment of 120 minutes duration, are stated to be satisfactory. The shell may be removed by centrifuging. In preparing an aqueous extract, the defatted moderately roasted bean or shell is preferably ground, and, after filtration, the extract is concentrated to a syrup or completely dried by spraying or in vacuo. One per cent of the dry extract may be mixed with the material. In the treatment of essential oils, e.g. orange oil, the bean or shell is about 10 per cent of the oil and is left in the oil until it is used. According to the Provisional Specification, the unroasted bean or shell may be used. The extract may be beaten into margarine or emulsified with the fat used in the preparation of margarine. The formation of resinous bodies and/or the development of colour and odour in petroleum hydrocarbons, especially cracked distillates, in storage, may be inhibited by heating with 5 per cent by weight of ground cocoa bean shell or an extract thereof.ALSO:Organic colouring matters and other materials which contain or consist of unsaturated organic compounds are preserved against deterioration by oxidation by incorporating in the material moderately roasted cocoa bean or moderately roasted cocoa bean shell so as to enable the material to absorb antioxidants therefrom. Alternatively an antioxidant-containing extract is obtained from the moderately roasted bean or shell by an evaporable solvent, e.g. water at 60-90 DEG C., the extract being incorporated, with or without concentration, in the material. A preliminary de-fatting extraction of the bean or shell with petroleum ether or carbon tetrachloride is desirable. In preparing an aqueous extract, the de-fatted moderately roasted bean or shell is preferably ground, and, after filtration, the extract is concentrated to a syrup or completely dried by spraying or in vacuo. One per cent of the dry extract may be mixed with the material. According to the Provisional Specification, the unroasted bean or shell may be used.ALSO:Rubber is preserved against deterioration by oxidation by incorporating therein moderately roasted cocoa bean or moderately roasted cocoa bean shell so as to enable it to absorb anti-oxidants therefrom. Alternatively an anti-oxidant containing extract is obtained from the moderately roasted bean or shell by an evaporable solvent, e.g., water at 60-90 DEG C. the extract being incorporated, with or without concentration, in the material. A preliminary de-fatting extraction of the bean or shell with petroleum ether or carbon tetrachloride is desirable. In preparing an aqueous extract, the de-fatted moderately roasted bean or shell is preferably ground, and, after filtration, the extract is concentrated to a syrup or completely dried by spraying or in vacuo. One per cent of the dry extract may be mixed with the material. According to the Provisional Specification, the unroasted bean or shell may be used.ALSO:Vegetable and essential oils, fats, organic colouring matter, rubber, and other materials which contain or consist of unsaturated organic compounds, are preserved against deterioration by oxidation by incorporating in the material, moderately roasted cocoa bean or moderately roasted cocoa-bean shell so as to enable the material to absorb anti-oxidants therefrom. Alternatively an anti-oxidant-containing extract is obtained from the moderately roasted bean or shell by an evaporable solvent, e.g. water at from 60-90 DEG C., the extract being incorporated with or without concentration, in the material. A preliminary defatting extraction of the bean or shell with petroleum ether or carbon-tetrachloride is desirable. In the treatment of an oil or fat, it is heated to 60 DEG C. with 2 to 10 per cent of moderately roasted bean or shell which is afterwards removed by filtration and re-used. In the case of a partially hydrogenated edible fat, the addition of 5 per cent, by weight, of defatted, ground, moderately roasted shell, and a heating treatment of 120 minutes duration, are stated to be satisfactory. The shell may be removed by centrifuging. In preparing a water extract, the defatted moderately roasted bean or shell is preferably ground, and, after filtration, the extract is concentrated to a syrup or completely dried by spraying or in vacuo. One per cent of the dry extract may be mixed with the material. In the treatment of essential oils, e.g. orange oil, the bean or shell is about 10 per cent of the oil and is left in the oil until it is used. According to the Provisional Specification, the unroasted bean or shell may be used. The extract may be beaten into margarine or emulsified with the fat used in the preparation of margarine. The formation of resinous bodies and/or the development of colour and odour in petroleum hydrocarbons, especially cracked distillates, in storage, may be inhibited by heating with 5 per cent by weight of ground cocoa-bean shell or an extract thereof.