SO₂ steeping is the main process which distinguishes the corn starch industry from the manufacturing of other starches. The effects of SO₂ as the steeping reagent have been reported by many chemists and researchers. However, no clear evidence has ever been presented to indicate what kinds of protein in the corn undergoes what changes and how it is solubilized and separated from the corn kernels. The present study was conducted to determine the degradation and behaviour of each corn protein as a result of steeping. The corn proteins were successively extracted from dry corn and from steeped corn with distilled water, a 0.5 M NaCl solution, 70% ethanol and a 0.1 N NaOH solution. Each fraction was analyzed for its nitrogen content and examined by gel filtration and trichloroacetic acid treatment. About 20% of the nitrogen in dry corn is usually extracted by the commercial steeping process. Comparing the various extracted fractions of dry corn and steeped corn, the watersoluble and the saline-soluble % nitrogen for both corns do not show much difference. The % nitrogen soluble in 70% ethanol increases greatly as a result of steeping. But the % nitrogen soluble in 0.1 N NaOH decreases greatly as a result of steeping because the 0.1 N NaOHsoluble nitrogen (protein) is gradually degraded to watersoluble, salinesoluble and 70% ethanolsoluble protein and peptides. The water extract contains 40% or more of the proteins and 50% of the peptides of dry corn, but when using steeped corn, it contains 8090% of the peptides and a few proteins.

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Lactic acid is naturally formed during commercial SO₂ steeping intended to soften the cell walls of corn. No research has been done to determine whether lactic acid plays an essential role in corn steeping. The nitrogen compounds were extracted from corn by steeping (lab scale) in either lactic acid or SO₂. As a result, the amount of nitrogen compounds extracted by lactic acid steeping was found to be about the same as that extracted by SO₂ steeping. Most of the lactic acid-extracted nitrogen was in the form of low molecular weight compounds (peptides), practically like the 502 steeping extract. In addition, the amount of nitrogen compounds extracted by successive lactic acid and SO₂ steeping operation is remarkably greater than with either steeping agent used individually. Starch separation tests were carried out by a sedimentation method using mill starches that were prepared by SO₂ steeping and lactic acid steeping. The separation results with the SO₂ mill starch were of course very good, but in the case of lactic acid steeping the starch separation was no good. Therefore, it is clear that lactic acid as a steeping reagent performs as well as SO₂ in the solubilization and disruption of the corn proteins, but it is nearly impossible to separate the starch from the corn endosperm.

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It was found that methyl salicylate (MS) was included in the vacant spaces among molecular chains of polysaccharides. The inclusion complexes were white and odorless powder. The standard method for preparation of the complex was shown in Fig. 1. Some conditions for the preparation were investigated: selection of effective carrier solvent; concentration of MS in methanol, the most effective solvent (Fig. 2); temperature and period for pre-air-drying (Fig . 4); influence of moisture in methanol and polysaccharide (Fig.5); influence of ethanol in methanol (Fig. 6); kind of host polysaccharide (Table 1). The maximal amount of MS included was about 150 mg/g. MS was most effectively extracted with methanol from complex (Tables 2 and 3). The complex was very stable against dry-heating at 100° under reduced pressure, but the content of MS in complex was gradually decreased in damp atmosphere (Fig. 7).

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It was indicated in the previous papers that the gelatinization temperature (GT) of starch in food and isolated starch could be determined successfully by differential thermal analysis (DTA). In the present investigation, the effect of salts and sugars on the GT of starch was studied by DTA in aqueous medium. NaF increased the GT, while NaCl, NaBr or NaI decreased it in a order of the periodic table. Na-carbonate and -bicarbonate had no influence on the GT, and nitrate and perchlorate decreased it, while sulfate, phosphate and thiosulf ate increased it strongly. The influences of salts of organic acids on the GT were relatively small, while sugars had great increasing effects on the GT. Difference between these substances in the influence on the GT could be demonstrated quantitatively by the critical concentration index defined by authors as the index of minimum concentration required to make a change of the GT. This index was in linear relation with the lyo tropic value and the hydration number of ions, and furthermore correlated very closely with the B-coefficient of salts. This suggests that the ability of salts to influence the water structure takes part in the gelatinization phenomenon of starch. Thermal Behavior of High Molecular Substances in Foods Part 3

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Although starch granules of roots and tubers were, in general, more resistant to the action of amylase than those of cereals, taro starch granules were highly susceptible and starch granules of banana, gingko and chestnuts were rather resistant to the action of pancreatin comparing with those of the normal corn. We also examined relative susceptibility to pancreatin of starch granules of 13 cultivars of legumes ( Vicia faba, Pisuna sativum var. arvense, Phaseolus vulgaris, Vigna sesquipedalis, Vigna angularis and Dolichos lablab) . These starch granules were, in general, less susceptible to the enzyme action than those of the normal corn . Starch contents of starchy legumes, soybeans and peanuts were 35-40, 0.8-1 .4 and 5.1% (on wet weight basis), respectively. The starch content of mung bean cotyledon decreased rapidly after 2-4 days germination. Decrease in starch content was confirmed by observation under a scanning electron microscope (SEM) of the dissected cotyledon of mung beans with or without germination. In the cotyledon of ungerminated mung beans many lumps of amyloplasts were observed and several starch granules with smooth surfaces were embedded in amorphous cementing materials in a cell . With the progress of germination the cementing materials disappeared and starch granules decreased in number. After 4 days of germination, although most starch granules had smooth surfaces, some granules had rough surfaces and some of them showed a hole at the end of the major axis . However, patterns of enzymatic erosion of the starch granules visible in the dissected endosperm of normal corn following the early germination period were seldom observed in the case of the cotyledon of germinating mung bean. By SEM observation starchy legumes and peanuts as same as mung bean seldom showed pattern of enzymatic erosion of starch granules in the dissected endosperm of normal corn. Approximately 50% of either potato or banana starch granules ingested by rats fed diets containing the starch granules as the main carbohydrate disappeared in rat bodies with making corrections for starches in feces and in contents of the gastrointestinal tracts. The intestinal enlargement caused by indigested starch granules was mainly due to hyperplasia. By SEM observation starch granules isolated from the digestive tracts of rats fed each one of diets con taining starch granules of banana, potato and Chinese yam (round-type) as the main carbohydrate showed typical patterns of the enzymatic attack, probably those of α-amylase attack, on their surface layers and inner portions. SEM observations of the cross-section of a grain of feces of rats fed each one of diets containing starch granules of banana, potato and Chinese yam (round type) revealed that damage of starch granules could be observed without the tedious procedure separating starch granules from feces.

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Several topics are briefly reviewed, which are selected from results in biochemical studies on polysaccharides made during past 30 years. Topics include discovery of isoamylase, biochemistry of dextran, pullulan and α-1, 3-glucan, as well as the amperometric titration of starch with iodine.

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