[Effect of various solvents on the extraction of protein fractions of beans (Phaseolus vulgaris)]. / Effecto de varios solventes sobre la extracción de las fracciones proteínicas del frijol (Phaseolus vulgaris).

A study was carried out to determine the effect of different solvents on the extraction of protein fractions in beans. Black bean protein was extracted with the following solvents: distilled water, 0.01 M sodium hydroxide, 0.05 M sodium chloride, and 70% ethanol. By using each solvent under different conditions, it was possible to establish the optimum ones for the best extraction and fractionation of proteins from leguminous seeds. These conditions were the following: one hour agitation at room temperature, three successive extractions with the same solvent, and a ratio of solid to solvent of 1:20 W/V. The effect of 24 different sequences of solvents upon the extraction of protein was also investigated. From the extraction point of view, the best sequence of solvents for extracting the protein was that where NaOH constituted the first solvent used; this sequence, however, has the disadvantage of extracting all the protein from the seed, making it impossible to separate other protein fractions by another solvent. If the purpose of the extraction is to separate different protein fractions, the best sequence of solvents is distilled water or sodium chloride in the first place, followed by ethanol and sodium hydroxide. The need for using standardized methodology for the fractionation of protein from seeds in order to obtain comparable data between research laboratories is emphasized.

[Biological behavior of protein fractions isolated from the common bean (Phaseolus vulgaris)]. / Comportamiento biológico de fracciones proteínicas aisladas del frijol común (Phaseolus vulgaris).

The purpose of this study was to determine the factors responsible for the low digestibility of bean proteins. To this effect, protein fractions were isolated from black beans through sequential extraction with distilled water, 70% ethanol and 0.01 M sodium hydroxide. Since the amount of protein extracted with the solvents was very low, it was practically impossible to carry out its biological evaluation in rats. Therefore, the protein fractions were added to casein diets in order to determine the decrease in casein digestibility due to the particular protein fraction added. The extracts and residues were heated and dehydrated prior to their incorporation in the rations. Nine rations were prepared. The first one was the control with casein only; 20% of whole bean flour was added to the 2nd; rations 3, 4 and 5 contained the water extraction residue, the water extract, and both, respectively; rations 6, 7 and 8 contained the ethanolic residue, the ethanol extract, and both, respectively. Finally, ration 9 was prepared with the NaOH residue. All the materials used as well as the rations were analyzed for their proximate composition and amino acid pattern. The results of the biological evaluation were as follows: casein and dry matter digestibility decreased significantly with the 2nd ration which contained 20% whole bean flour, effect which was significant also in rations containing either the water or the ethanol extract. This effect is attributed to the antiphysiological factors present in the beans which are resistant to heat treatment. The protein efficiency ratio was lower for the rations prepared with the residues from water and ethanol extractions (3 and 6) than for casein; these results are attributed to the lysine and methionine deficiency in the protein fractions, complicated by a lower protein intake. The lowest nutritive value was found in group 7, which was fed the ration containing the ethanol extract, but when the latter was added together with its residue (ration 8), the PER was superior than for ration 7, possibly due to a higher content of methionine and lysine in ration 8. Finally, it is suggested that better results could be obtained by using higher amounts of beans and their protein fractions in the ration.

Efecto de varios solventes sobre la extraccion de las fracciones proteinicas del frijol (Phaseolus vulgaris). / Effect of different solvents on the extraction of protein fractions of beans (Phaseolus vulgaris)

En el presente trabajo se informa de un estudio relacionado con el fraccionamiento por solubilidad de las proteinas del frijol negro (Phaseolus vulgaris), variedad S-19N, usando diferentes solventes: agua, hidroxido de sodio 0.0l M, cloruro de sodio 0.05 M, y etanol al 70%