Osmotic potential and soluble solids concentration in onion (Allium cepa) bulbs

Abstract

Non-structural carbohydrate composition of onion (Allium cepa L) bulbs is known to vary between varieties according to soluble solids concentration (SS), which may reduce the effect of SS on osmotic potential. This was confirmed in an experiment where osmotic potential (+*) was determined psychometrically, and SS concentration refractometrically, in juice from entire, mature bulbs of 35 varieties of onion. 'Fresh market' varieties ranged in mean SS from 63 to 125gkg-and in mean $* from -0.97MPa to -1.17MPa, whereas 'dehydrating' varieties ranged in mean SS from 167 to 227 g kg-and in mean JI. from -1.23 MPa to -1.41 MPa. Compared to sugar solutions of constant composition, with increasing SS, there was a relatively slow decline in +* toward a lower limit at the SS levels of dehydrating varieties. The relationship between JI. and SS was explained equally well (r2 = 0.83; DF = 172) by non-linear and bent-stick regression models, the latter indicating breakpoints close to the SS level separating fresh market variety samples from those of dehydrating varieties.Variety differences in the relationship between JI, and SS indicated among dehydrating varieties in particular are worthy of further investigation because of their possible physiological and quality implications.

Measurement of the distribution of non‐structural carbohydrate composition in onion populations by a high‐throughput microplate enzymatic assay

“…1 -3,11-13,15 DM and soluble solid (SS) contents of high-and low-DM genotypes are linearly correlated and exhibit a strong positive correlation with fructan content and a negative correlation with reducing sugars. 2,10 High-DM onions (>150 g kg −1 DM) containing low hexose concentrations are required in the dehydrating industry, as they have a direct impact on the energy required for drying and on the colour of dehydrated products. Refractometry (SS) 16 and near-infrared (NIR) spectroscopy 17 have been widely used in dehydration onion breeding programmes to determine percentage DM in onions.…”

Genetic analyses of correlated solids, flavor, and health-enhancing traits in onion (Allium cepa L.)

“…Solids content is related to onion¯avor, texture, storability, and is important to the dehydration industry (Suzuki and Cutclie 1989;Sinclair et al 1995b). The predominant non-structural carbohydrates in onion bulbs are glucose, fructose, sucrose, and fructans of low to medium molecular weight (Darbyshire and Henry 1978, 1979Nilsson 1980).…”

Genetic Analyses of Soluble Carbohydrate Concentrations in Onion Bulbs

“…Genetic studies of soluble carbohydrates in onion bulbs have revealed significant phenotypic and genotypic correlations among soluble solids content, DW, and pungency (Galmarini et al, 2001;Lin et al, 1995;Simon, 1995;Sinclair et al, 1995;Suzuki and Cutcliffe, 1989). One region on chromosome 5 accounted for significant amounts of variation for these traits, showing positive additive effects of alleles from the high DW parent (Galmarini et al, 2001).…”