PubMed · 5529788
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H Oka. 1970. [Digestion-absorption test].. https://pubmed.ncbi.nlm.nih.gov/5529788/
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Simultaneous extraction and derivatization of carbohydrates was performed by mixing dry ground plant tissue with derivatization reagents in pyridine; trimethylsilyl derivatives were analyzed by gas-liquid chromatography. This "direct analysis" was compared to analysis of samples prepared by exhaustive ethanol extraction of the same ground plant tissues. Comparisons included leaf blades from apple, grape, corn, and tomato and leaf blade, petiole, stem, and pod tissues from soybean plants. Direct analysis gave superior quantification of sucrose, glucose, and fructose because of sucrose hydrolysis during ethanol extraction. Sucrose hydrolysis was highly variable among plant species and use of hot ethanol at the first extraction step reduced sucrose hydrolysis but did not always abolish it. Sucrose hydrolysis was probably due to the activity of hydrolytic enzymes in 75% ethanol at room temperature. Direct analysis was inferior for the quantification of cyclitols in the fibrous tissues of soybean but provided acceptable results for cyclitol analysis in leaf blade tissue. When the time for extraction/reaction was extended from 40 to 60 min, some improvement in recovery of cyclitols was observed, but recovery remained 10 to 20% below that obtained with exhaustive ethanol extraction. Mannitol was vacuum infiltrated into the five types of leaf tissue and recovery averaged 100% by the direct method relative to ETOH extraction for apple, grape, corn, and soybean leaves but was only 76% for tomato leaves. Direct analysis provides very large time savings and is clearly the method of choice when the analysis of large numbers of samples of plant tissues for carbohydrate composition is required.
The controlled fermentation of peeled, blanched garlic, using a starter culture of Lactobacillus plantarum, was studied and compared with that of unblanched garlic. Blanching was carried out in hot water (90 degrees C) for 15 min. The starter grew abundantly in the case of blanched garlic, producing mainly lactic acid and reaching a pH of 3.8 after 7 days, but its growth was inhibited in unblanched garlic. Ethanol and fructose, coming from enzymatic activities of the garlic, and a green pigment were formed during the fermentation of unblanched garlic, but not of blanched garlic. The blanched garlic fermented by L. plantarum, even without a preservation treatment (pasteurization), was microbiologically stable during storage at 30 degrees C in an acidified brine (approximately 3% (w/w) NaCl and pH 3.5 at equilibrium), but fructans were hydrolyzed. The packed fermented product and that obtained by direct packing without fermentation were not significantly different with regard to flavour.
Fourier transform infrared microspectroscopy (FTIR) was used to study glasses of pure carbohydrates and in the cytoplasm of desiccation tolerant plant organs. The position of the OH stretching vibration band (vOH) shifted with temperature. Two linear regression lines were observed in vOH against temperature plots. The temperature at the point of intersection between these two lines coincided with the glass transition temperature (Tg), as determined by other methods. The temperature at the intersection point decreased with increasing water content, which further validates that, indeed, Tg was observed. Tg values that were determined for dry glucose, sucrose, maltose, trehalose and raffinose glasses were 27, 57, 91, 108 and 108 degrees C, respectively. The shift of vOH with temperature, the wavenumber-temperature coefficient (WTC), was higher in sugar glasses having higher Tg. This suggests that glasses are more loosely packed when they have higher Tg. For Typha latifolia pollen and dried Craterostigma plantagineum leaves we obtained similar vOH vs. temperature plots as for carbohydrate glasses, indicating that a glass transition was observed. The Tg in dry pollen was ca. 45 degrees C and in dry plant leaves ca. 65 degrees C, with WTC values comparable to those observed in the carbohydrates. The Tg values in these tissues decreased with increasing water contents. Our data suggest that the carbohydrates that are present in the cytoplasm are primary factors contributing to the glassy state. We conclude that FTIR provides new insights in the structure of glasses in carbohydrates and in biological tissues.