Compensación cinética y termodinámica del pardeamiento no enzimático de zumos clarificados de limón

IF 1 Q3 AGRICULTURE, DAIRY & ANIMAL SCIENCE
R. Ibarz, A. Garvín, Oriol Tomasa, Albert Ibarz
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Abstract

This paper presents a study on kinetic and thermodynamic compensation to evaluate the kinetics of non-enzymatic browning of clarified lemon juices. In a previous work, the kinetic constants of browning were presented using the evolution of the absorbance at 420 nm (A420) and luminosity (L*) for different soluble solids contents (64.6; 50; 35; 20 and 10 ºBrix) and different working temperatures (70, 80, 90 and 95 ºC). The parameters of the Arrhenius equation were obtained by fitting the kinetic constants and temperatures. The variation of lnK0 with Ea follows a linear trend, so there is kinetic compensation, with isokinetic temperature values being 126.6 ºC and 149.7 ºC for A420 and L*, respectively. The transition state equilibrium constants were determined using the Eyring equation for each soluble solids content and each temperature. The equilibrium constants were adjusted to the Van't Hoff equation and the set of pairs of estimated values for the activation enthalpy and the activation entropy also followed a straight line, which causes thermodynamic compensation, with isoequilibrium temperatures of 112.8 ºC and 136.3 ºC for A420 and L*, respectively. It was concluded that the browning mechanism is the same for the ranges of soluble solids content and temperature studied. Since all isokinetic and isoequilibrium temperatures were higher than the working temperature values, it was also concluded that the control was enthalpic for all cases. To avoid the deterioration of these juices, it is advisable to intervene in the working temperature, trying to ensure that the heat treatment is carried out at the lowest possible temperature.
澄清柠檬汁非酶促褐变的动力学和热力学补偿
本文介绍了一项关于动力学和热力学补偿的研究,以评估澄清柠檬汁非酶促褐变的动力学。在之前的一项研究中,利用 420 纳米吸光度(A420)和光度(L*)的变化,给出了不同可溶性固体含量(64.6;50;35;20 和 10 ºBrix)和不同工作温度(70、80、90 和 95 ºC)下褐变的动力学常数。通过拟合动力学常数和温度,得到了阿伦尼乌斯方程的参数。lnK0 随 Ea 的变化呈线性趋势,因此存在动力学补偿,A420 和 L* 的等动力学温度值分别为 126.6 ºC 和 149.7 ºC。使用艾林方程确定了每个可溶性固体含量和每个温度下的过渡态平衡常数。根据 Van't Hoff 方程对平衡常数进行了调整,活化焓和活化熵的估计值对也遵循了一条直线,这导致了热力学补偿,A420 和 L* 的等平衡温度分别为 112.8 ºC 和 136.3 ºC。由此得出结论,在所研究的可溶性固体含量和温度范围内,褐变机理是相同的。由于所有等动力学温度和等平衡温度都高于工作温度值,因此还得出结论,所有情况下的控制都是焓控制。为避免这些果汁变质,建议对工作温度进行干预,尽量确保在最低温度下进行热处理。
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来源期刊
Scientia Agropecuaria
Scientia Agropecuaria AGRICULTURE, DAIRY & ANIMAL SCIENCE-
CiteScore
3.50
自引率
0.00%
发文量
27
审稿时长
12 weeks
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