A FURFURAL-YIELDING SUBSTANCE AS A SPLITTING PRODUCT OF PROTOPECTIN DURING THE RIPENING OF FRUITS

While studying the CARRE (4) procedure for the determination of protopectin, the writer observed that the filtrates from the calcium pectates contained a considerable quantity of a fturfural-yielding substance. At about the same time EHRLICH'S (9) preliminary paper came to the writer's attentioni. In this paper EHRLICII showed that the protopectin (he calls it "pectin") of sugar beets and a considerable number of other vegetables and fruits is split by boiling water into two fractions-"a levo-rotatory araban," and "a calcium-magnesium salt of pectic acid." A mixture of the two, called "hydrato-pectin" is obtained by boiling the plant tissues, previously freed from sugars, with water and evaporating the extract to dryness on the water batlh. The araban is then separated from the pectic substanices by extraction with 70 per cent. alcohol. The work of ElIRLICII (11) on1 sug,ar beets has been confirmed, in general, by SMOLENSKI (20) anid his co-workers. The exact nature aind significance of EHRLICH 'S work seems not to be very w-ell appreciated by other investigators in this field. For example, MIcKINNIS (16) apparently fails to distinguish between the extraneous "araban," soluble in 70 per cent. alcohol, and the arabinose contained witili the pect-in molecule (17). It is likewise not clear from DORE'S (8) discussion that lhe distinguished between the two. AVICKMANN (21) found a fturfural-forming complex in his pectic acid filtrates but ascribed it to disintegration of pectin. In spite of EHRLICH'S work, EMMETT (12) assumes that no alcohol-soluble substance forms from the ilnsoluble cell wall material of pears during ripening. However, she is at a loss to explain a certain unidentified constituent in the juice which makies up 20 to 30 per cent. of the dry weight. It should be noted that EIIRLICII uses a different nomenielature from that generally used, and from that proposed by the Committee (6) on Nomenclature of Pectic Substances. Thus his "pectin" corresponds to the protopectin of that committee report and his "calcium-magnesium salt of pectic acid" to the pectin. This unfortunate difference in terminology is, no doubt, largely responsible for the present confusion and the failuire to draw correct deductions from EHRLICII'S work. 'Approved for publication by the Director of the Experimiienit Station.