It was indicated in the previous papers that the gelatinization temperature (GT) of starch in food and isolated starch, and the effect of salts and sugars on the GT could be determined successfully by differential thermal analysis (DTA). In the present investigations, the authors studied the effect of salt retained by starch granule in neutral salt solutions; Na₂SO₄, NaCI and NaBr solns. on the gelatinization of starch. The following findings were obtained . 1. The content of water retained by starch granule in Na₂SO₄ soln. was smaller than the control (in water), while the retained water content in NaCl soln. indicated a similar level, and an increased level in NaBr soln. The content of salt retained by starch granule was relatively low in Na₂SO₄ soln, while considerably high in NaCI and NaBr solns. 2. The retained Na₂SO₄ brought about a GT rise from 62°C to 80°C, while the retained NaCI or NaBr decreased the GT of the starch from 62°C to 56°C or 41°C respectively . Although the retained Na₂SO₄ did not affect essentially the endothermic heat of gelatinization, the retained NaCI and NaBr decreased it to about 70% and 50% of the control, respectively. Such decreases were accompanied by the corresponding decreases of the sharpness of X -ray diffraction . 3. The polarization pattern of Na₂SO₄-treated starch granule still retained a part of original pattern at ceased point of DTA-endotherm, while NaBr-treated starch granule had lost a part of original polarization pattern already before heating by DTA. From these observations, it is suggested that the salt retained by starch granule affects the structural stability of starch micelle.

View full abstract

In order to clarify the machanism of digestion of amylomaize starch granules by rats, some properties of the starch remaining in the digestive tract and the activities of starch-degrading enzyme in the intestine were examined by using the animals fed on the starch granules (amylose content 49.3%). The starch granules were isolated from stomach, small intestine, cecum, large intestine and feces at various intervals after feeding. The elution patterns of the starches on a Sephadex G-50 column showed that low molecular weight components accumulated and increased gradually with progress of digestion. The iodine coloration of the starches decreased, and the λmax of the starch-iodine complex shifted to a shorter wavelength during the same process. These findings as well as of the previous studies suggest that the amorphous parts of amylomaize starch granules were preferentially degraded in the rat intestine, and the crystalline parts in the granules accumulated in the residual starch. The amylase activities in the intestine of rats fed on amylomaize starch granules were detected not only in the small intestine but in the cecum and large intestine, whereas the amylase activities in the intestine of the animals fed on normal corn starch were present mostly in the small intestine. It seems that amylomaize starch granules were digested through the whole intestine. The digestive capacity for mylomaize starch granules of the cecum contents tended to be larger than that of the small intestine contents, as compared on the same basis of amylase activity. These results suggest that the starch-degrading enzyme systems are different in these organs.

View full abstract

Globular particles (6-7 μm in diameter) precipitated from the hot solution, 10%, of a commercial oxidized corn starch. The following properties of the precipitate and related substances were investigated: (1) X-ray diffraction pattern (Fig . 2 and Table 1); (2) intrinsic viscosity in 1N KOH and dimethyl sulfoxide (Table 2); (3) absorption spectrum of colour solution with iodine (Fig. 3 and Table 3); (4) iodine affinity value (Table 3); (5) chain length by the oxidation method with periodate (Table 4); (6) limit of β-amylolysis (Table 5) . From those results, it was found that the precipitate was the microcrystal of amylose-lipid complex in which mean chain length of amylose was about 100 anhydroglucose unit.

View full abstract

The author described the relationship between the amount of sorption water and crystallinity or heat of sorption in starch granules. The values of the monolayer sorption water in starch were 7-8% of starch and saturated sorption water would be six molecules for each glucose residue and the crystallinity of starch were found to be from 31 to 45% by means of moisture regain method . The crystallinity measured by means of X-ray method increased with increasing sorption water and seemed to become the values by means of the moisture regain and specific volume methods . The heat of crystallization of starch were as follows: 0.4-0 .5 kcal (mol. glucose residue)^-1 for potato, sweet potato and tapioca starches, and 1.9-2.2 kcal (mol. glucose residue)^-1 for corn and wheat starches . The amorphous portion in sweet potato and tapioca starches were 1.2 times as much as that of wheat and corn starches according to the results as to integral net sorption heat .

View full abstract

There are three typical relations between carbohydrates and proteins . 1) Starch and proteins, such as wheat starch and gluten in dough for bread making and fish meat and starch in Kamaboko, where their viscosity and elasticity are strengthened by each other . 2) Proteins and ionic carbohydrate polymers, such as whey proteins and carboxymethyl-cellose and gluten and microbial polysaccharides, where the proteins are aggregated and precipitated in a dilute solution . 3) Proteins and oligosaccharides, such as sucrose and Surimi (fish meat jelly) and egg proteins, where the proteins are protected by oligosaccharides against the denaturation of freezing, heating or acidic conditions. These relations in food processing and fundamental studies are reviewed and summarized .

View full abstract

There is 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 study was conducted to determine the degradation and behaviour of each corn protein before and after steeping. About 20% of the nitrogen in dry corn is usually extracted by the commercial steeping process. The water-soluble nitrogen fraction in dry corn contains 40% or more of the proteins and 50% of the peptides, but in wet corn it contains 80-90% of the peptides and few proteins. The % nitrogen soluble in 70% ethanol increases greatly as a result of steeping. But the nitrogen soluble in 0.1 N NaOH decreases simultaneously. The nitrogen compounds were extracted from corn by steeping (lab scale) in either lactic acid or SO₂. As a result, most of the lactic acid-extracted nitrogen was in the form of low molecular weight compounds (peptides), practically like the SO₂ steeping extract. However, when carrying out the starch separation using mill starches, in the case of lactic acid steeping the starch separation was no good. Therefore, lactic acid 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.

View full abstract