Effect of storage on fructan and fructooligosaccharide of onion (Allium cepa L.).

The purpose of this study was a comparative examination of the fructan and fructooligosaccharide (FOS) content of different varieties of onions (Allium cepa L. cv. Sturon, Hysam, Durco, Grano de Oro, and Caribo) and the changes produced during their commercial storage. In fresh onions, the Grano de Oro variety presented a remarkably different behavior, showing low contents of total fructans and FOS and high levels of reducing sugars. In the other varieties, Sturon, Hysam, Durco, and Caribo, fructans were the main carbohydrates, the lowest polymerized FOS being the major oligomer. Storage period caused in these varieties important increased levels of free fructose attributed to fructan hydrolysis. Maleic hydrazide treatment had no significant effect in avoiding the hydrolysis of fructans during storage conditions for the Sturon variety. Varieties with >16% dry matter or 15% soluble solids contents could be stored for 6 months at 0 degrees C and 60-65% relative humidity.

Modifications to physicochemical and nutritional properties of hard-To-cook beans (Phaseolus vulgaris L.) by extrusion cooking.

The objective of this work was to evaluate extrusion cooking as a means to improve the nutritional properties of Phaseolus vulgaris L. that had been stored either at 42 degrees C and 80% relative humidity for 6 weeks or for periods >1 year in cereal stores in tropical conditions. Storage under these conditions resulted in an increase in cooking time increased (7.7- and 12-fold, respectively) as a result of development of the hard-to-cook (HTC) defect. Single-screw extrusion of the milled beans was carried out at four barrel temperatures and two moisture contents. The extrudate bulk density and water solubility index decreased with increasing temperature, whereas the water absorption index increased due to the higher proportion of gelatinized starch in the extruded samples. Both fresh and HTC beans contained nutritionally significant amounts of lectins, trypsin, and alpha-amylase inhibitors, which were mostly inactivated by extrusion. Extrusion also caused a considerable redistribution of insoluble dietary fiber to soluble, although the total dietary fiber content was not affected. Changes in solubility involved pectic polysaccharides, arabinose and uronic acids being the main sugars involved. Stored beans subjected to extrusion cooking showed physical and chemical characteristics similar to those of extrudates from fresh beans.