This invention relates to a lipid powder having a cross-linked coating thereon and employed as a raw material or an additive in the sectors of foodstuffs or feeds, and to a process for producing the lipid powder.
Researches have long been made for evolving a suitable process for preparing lipid powders. Recently, oily substances exhibiting certain physiological activities, such as eicosapentaenoic acid (EPA) or tocopherol, are attracting public attention since they have proven properties favorable to health and prevention of senility. It has been desired that these substances be available in the form of lipid powder, because they are stable and easy to handle when in this form. For example, there is known a process of emulsifying an oily substance in an aqueous phase containing protein, hydrocarbon, cellulose, gum or the like dissolved therein and forming powders of the oily substance by atomizing and drying, as disclossed in Japanese Laid-open Patent Publications Nos. 1415/1966 and 11040/1975. The process, however, has disadvantages in that the powder obtained thereby has a low barrier capacity to oxygen, while the oily substances containing higher unsaturated fatty acids are oxidized in a shorter time to produce toxic components or to emit bad odor.
There is also known a process for having the oily substance included in cyclodextrin or cyclic glucan, as disclosed for example in Japanese Laid-open Patent Publications Nos.41395/1984, 34156/1985 or 33127/1986. This process again is disadvantageous since the oily substance is insufficient in stability although the emission of bad smell is inhibited by the effect of masking.
There is also known a lipid powder using a heat-coagulable protein as a coating film, as disclosed in Japanese Laid-open Patent Publication No.47643/1985. The powder has, however, a drawback that the oily substance is oxidized in the course of heat treatment.
A microcapsule produced by the coacervation process is disclosed in Japanese Laid-open Patent Publication No. 126016/1986. Although the oxygen barrier properties are improved by curing, the process disclosed therein does not lend itself to mass production because of the complicated operation and elevated costs.