Kinetics and hydrolysis parameters of total fructooligosaccharides of onion bulbs: effects of temperature regimes and cultivars
2007
Benkeblia, Noureddine | SHIOMI, NORIO | Ōsaki, Mitsuru
This work studied the percentage of hydrolysis, observed hydrolysis rate constant (kobs), half-life time (t₁/₂) and kinetics of degradation of the total fructooligosaccharides (FOS) of three different onion bulb cultivars (Yellow Spanish, Red Amposta and Tenshin) kept during 6 months under three temperature regimes, 10, 15 and 20C. The percentage of hydrolysis of FOS was higher at 20C than at 10C and ranged from 47 to 58% at 10C, from 63 to 68% at 15C and from 74 to 83% at 20C. The kobs ranged from 27 x 10⁻³ to 36 x 10⁻³/week at 10C and from 41 x 10⁻³/week to 47 x 10⁻³/week at 15C, while at 20C, it was high and was about kobs 56 x 10⁻³/week.. The t₁/₂ decreased when temperature increased, and varied from 19.5 to 26.0 weeks at 10C, from 14.6 to 16.8 weeks at 15C and from 9.4 to 12.3 weeks at 20C, indicating that high degree of polymerization (DP) FOS have shorter lives than low DP FOS. Linear regression and kinetics of hydrolysis have shown that FOS hydrolysis is higher at 20C, with a coefficient of regression ranging between 0.87 and 0.99. Apparently, FOS hydrolysis is temperature independent, and storage time had more effect on the higher DP FOS than on the lower DP FOS.
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