Kinetics of ascorbic acid loss during hot water blanching of fluted pumpkin (Telfairia occidentalis) leaves

Abstract

The kinetics of thermal degradation of ascorbic acid in fluted pumpkin leaves were investigated from 60 to 90°C (pH 5.0 to 6.5). Ascorbic acid degradation was modeled as a first order rate reaction with the rate constants increasing with increase in pH of the medium. The pH and temperature dependence of the rates of destruction gave highly significant correlations when analyzed by the thermal resistance and activated complex reaction rate methods. Activation energy (Ea) ranged from 41.2 to 18.2 kJ/mol while D-values ranged from 103.3 to 22.4 min. The changes in activation energy affected K o values which ranged from 5.98 × 10 4 to 41.7 min -1 .

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“…At refrigerated temperatures, the loss of vitamin C in broccoli was much higher than capsicum, whereas comparable losses were observed at 20 o C. In the case of orange juice stored at 10 o C, the rate constant was observed as 4.63Ö10 −7 s −1 (Calligaris et al, 2012). In the case hot water blanching of pumpkin at pH 6.5, the rate constant increased from 8.10Ö10 −4 to 1.37Ö10 −3 s −1 when blanching temperature increased from 60 o C to 90 o C (Ariahu et al, 2011). The reaction rate constant of cherry juice increased from 3.12Ö10-4 to 1.00Ö10-3 s-1 with increasing temperatures (75, 80, 85, 90 and 95 o C) (Jirasatid & Noipant, 2015).…”

“…The high activation energy of vitamin C in broccoli implied that the deterioration was more sensitive to temperature as compared to the vitamin C degradation in guava, mango, and marula pulps. The activation energy of ascorbic acid loss during pumpkin blanching (60-90 o C) varied from 16.9 to 41.2 kJ/mol, while pH increased from 5.0 to 6.5, respectively (Ariahu et al, 2011). The pH of the fresh broccoli was measured as 6.8 .…”

“…Most of the studies determined percent losses during a predetermined storage time. There are relatively few reports available in the literature on the degradation kinetics of vitamin C in fruits and vegetables (Ariahu, Abashi, & Chinma, 2011). Yet the reaction order, rate constant, and activation energy are essential for predicting food quality loss during storage, as well as thermal processing (Nisha, Singhal, & Pandit, 2005).…”

Monitoring and Optimization of the Process of Drying Fruits and Vegetables Using Computer Vision: A Review

“…Tomato, indeed, after drying at 75 • C loses about half of its original AA content [34]. Furthermore, it has been observed, in a study on fluted pumpkin leaves, that high temperature over a short-time at low pH leads to a better retention of AA than a lower temperature over a long process at high pH [35]. During hot-air drying, vitamin C losses are greater than the ones related to freeze drying [36].…”

Application of dhurrin for kinetics and thermodynamic characterization of linamarase (β-glucosidase) genetically engineered from <i>Saccharomyces cerevisiae</i>.

“…These syndromes are of serious public health concern, especially in immune -compromised populations in African countries such as; Nigeria, Congo, Mozambique, Rwanda, South Africa and Tanzania (Akintonwa and Tunwashe, 2009). Cyanogenic glucosides undergo degradation reaction catalyzed by specific β-glucosidases which were characterized by various authors who used both kinetics and thermodynamic parameters including; order of reaction, rate constant, frequency factor, activation energy, enthalpy, entropy and the isokinetic temperature respectively from mathematical models (Ariahu et al, 2010., Ariahu et al, 1997., .Doungkamol et al, 2006., Fan et al, 1985., Legras et al, 1989., .Mkpong et al, 2000and Ikya, et al,2012a. The enzyme catalyzed reactions can be described adequately by various best fit mathematical models initially with kinetic models which generate the reaction rate constants that are fitted into the thermodynamic models of Arrhenius and absolute rate models to derive the thermodynamic parameters (Ikya, et al,2012a).…”