Oat Tocols: Concentration and Stability in Oat Products

Cereal Chem. 72(l):21-24 To determine the stability of tocols (vitamin E) in oat products under envelopes than in jars at room temperature, indicating that air may be various storage conditions, several oat products were stored in jars at involved in the degradation process. a-Tocopherol and a-tocotrienol -24° C or in jars or envelopes at room temperature for up to seven months. decreased faster than the other homologues during room temperature At approximately monthly intervals, products were ground and tocols storage in envelopes, indicating differential stabilities. Analysis of handwere extracted with methanol and analyzed by high-performance liquid dissected fractions indicated that the germ was the location for most chromatography. Tocols were stable for seven months in all products of the aand y-tocopherol. Tocotrienols were concentrated in the endoin jars at -24° C. At room temperature, all tocols degraded in all processed sperm and absent from the germ. products, but were stable in undried groats. Tocols degraded faster in Tocols (vitamin E) occur in at least eight naturally occurring forms, a-,(x -, ,-y-, and 8-tocopherol and a-, ,8-, By-, and 6-tocotrienol (Barnes 1983a). These tocols are physiologically active in alleviating symptoms of vitamin E deficiency. Vitamin E is an important antioxidant and free radical scavenger, and its presence has been linked to prevention of chronic disease and premature ageing, cancer, cardiovascular disease, and stroke (Packer and Fuchs 1993). Recently, several reports have implicated tocotrienols as cholesterol synthesis inhibitors (Qureshi et al 1986, Pearce et al 1992, Wang et al 1993). Cereal grains are important sources of tocols. Total tocol concentration in oat ranges from about 20 to 30 mg kg-', with a-tocotrienol as the predominant homologue (Lasztity et al 1980, Barnes 1983b, Peterson and Qureshi 1993). However, there is little information about the effects of processing and storage on the tocol concentration in oat. The production of rolled oats had little effect on a-tocopherol concentration, but more extensive processing resulted in substantial losses (Herting and Drury 1969). Piironen et al (1986) found 32 mg kg-' total tocols in rolled oats with a distribution of homologues similar to that of oat grain, but in puffed oats, the a-tocotrienol concentration was lower. In wheat flour and rye and barley meals, tocols degraded with time (Piironen et al 1988, Tyopponen and Hakkarainen 1985), but they were stable in intact barley grain over 10 months (Hakkarainen et al 1983). A six-year stored oat grain sample was 73% lower in a-tocopherol than one of recent harvest (Herting and Drury 1969). 'Cooperative investigation of the U.S. Department of Agriculture, Agricultural Research Service and the University of Wisconsin Agricultural Experiment Station. U.S. Department of Agriculture, Agricultural Research Service, Cereal Crops Research, Madison, WI. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. American Association of Cereal Chemists, Inc., 1995. The objective of this study was to examine the effects of different storage conditions on the stability of tocols in unprocessed oat groats and several oat products. Tocol concentration of handdissected oat groats was also measured to explain differences observed among some of the oat products. MATERIALS AND METHODS Freshly processed samples of oat groats and products (undried groats, dried groats, flour, bran, rolled oats, quick oats, and instant oats) from one production date were obtained from The Quaker Oats Company. Briefly, the processing of undried groats is as follows. Groats are heated from 82 up to 105-115°C over 90-120 min, driving the moisture down 7-9%. For quick and instant oats, the dried groats are steel cut. Then whole or cut groats are steamed for 8-12 min, bringing the moisture back to 10-11%, and then rolled. Rolled oat flakes, produced from whole groats, are thicker than quick and instant oat flakes. Bran and flour are produced by grinding and sieving quick oats. The coarse outer layers of the endosperm that are held on a 540-jim sieve are defined as bran, and the finer starchy endosperm material that passes through the sieve is defined as flour. Moisture levels of the samples as received were determined, and the samples were subdivided into jars or paper coin envelopes for storage. Three storage conditions were compared: capped jars at -24°C, capped jars at room temperature, and envelopes at room temperature. Immediately upon receipt of the samples, and at approximately monthly intervals thereafter, a sample of each product from each storage condition was analyzed in duplicate. At seven months (the final sampling), two samples of each product were analyzed in duplicate. Extraction and analysis of the groat and product samples for tocols was previously described (Peterson and Qureshi 1993). Briefly, duplicate 0.5-g samples were ground and extracted with methanol. Supernatants were dried under vacuum, and the residues were redissolved in hexane. Tocols were separated by Vol. 72, No. 1, 1995 21 high-performance liquid chromatography (HPLC) on a silica column using a mobile phase of 0.5% isopropanol in hexane and detected fluorimetrically. Ogle oat kernels were hand-dehulled with a small wringer; the groats were tempered in a petri dish; and germs excised with a small spatula. Samples (0.5 g for endo-