Crystallization behavior of rapeseed oil during isothermal storage was investigated by dilatometry, transmitted light intensity measurement, and differential scanning calorimetry. The volume and transmitted light intensity of the oil samples changed significantly after a certain period (induction period) during isothermal storage. In order to explain these changes, a kinetic model for the crystallization of rapeseed oil was proposed by assuming that stable crystals are formed through meltmediated transition and metastable crystals grow via an "autocatalytic" mechanism. The crystallization process of rapeseed oil is well represented by the model, and it reasonably explains the peculiar relationship between the storage temperature and the induction period for crystallization.

INTRODUCTION Lipids have wide applications, including in foods, pharmaceuticals, and cosmetics. In food products, lipids play important roles not only as an essential nutrient for humans 1 but also as a preservative 2 and heating medium 3 5. Furthermore, lipids also improve the taste and texture of food for enrichment of our diet 4, 5. Controlling lipid crystallization is important during lipid refining, and during production and preservation of lipid-containing foods. In the lipid refining process, the precipitation of lipid crystals with a lower liquid-phase content is required to improve refining efficiency 5, 6. The fine appearance and texture of foods with high-lipid content such as chocolate are created by appropriately controlling crystal polymorphism 7. The appearance or texture of dressings and chocolate can be spoiled by crystal growth or polymorphic transition during storage 8, 9. It is also reported that lipid crystallization could affect its oxidation 10. Studies on crystallization behaviors have been focused on many factors, such as the time at which lipid crystallization starts, the crystallization rate, crystalline polymorphs, polymorphic transition, crystal morphology, crystal size,

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Direct measurement of protein digests by fast atom bombardment mass spectrometry was examined in detail under various conditions such as with different amounts of sample and kinds of matrix. The results indicated that (i) signals of peptides covering over 90% of the protein sequence could be detected in the mass spectrum; (ii) almost all signals of peptides including those of over 3000 u could be recorded with about 5 p,g of protein digest; (iii) a peptide containing a cystine residue(s) gave the signal of the mother peptide together with that of its fragments formed by cleavage of the disulfide linkage.