Mathematical correlations between selected quality attributes and electrical parameters of apple juice

Abstract

This study aimed at determining mathematical correlations between total soluble solids (TSS) content, content of organic acids (OA), pH value (pH), and density (D) of apple juice and their electrical conductance and capacitance using the RCC equivalent model of food products (resistance and capacitance). Linear correlations were determined between total soluble solids content, organic acids content, and density of aqueous solutions of the apple juice concentrate and values of their impedance (Z) and admittance (Y) in a frequency from 100 to 100,000 Hz; and their equivalent parallel capacitance (Cp) at frequencies of 100, 120, and 1,000 Hz; as well as their equivalent series capacitance (Cs) at frequency of 100,000 Hz. It was concluded that the correlations obtained from grounds for future studies on the development of a method for detecting adulterations (through watering) of apple juices based on measurements of electrical parameters, including the impedance or admittance. Practical applications Due to increasing requirements for the food quality and safety, as well as an increased demand for apple juice, many research works on the development of modern techniques for identification, detection of adulteration, and predicting its quality have been undertaken. Taking this into account, the research was undertaken to determine the mathematical relationships between selected quality attributes of apple juice (TSS, organic acids, pH, density) and their electrical parameters. The obtained significant mathematical correlations (r > 0.87 and p ≤ 0.01), indicate that the quality of apple juices can be predicted on the basis of simple impedance and admittance measurements at f = 100 Hz. These dependencies also justify the use of the RCC electric model for predicting the basic attributes of the apple juice quality, which in the future will make possible the development of a method for detecting its adulteration with water. On this basis, a relevant patent has been yet obtained.

Analysis of Selected Physicochemical Properties of Commercial Apple Juices

“…The two-way analysis of variance showed a statistically significant only the apple variety density of apple juices. The obtained data correlate well with the results obtained by other authors.Żywica et al [30] marked the density of apple juices in the range of 1.034-1.051 g•cm −3 , Kobus et al [31] 1.034 to 1.041 g•cm −3 , and Nadulski et al [32] 1.028 to 1.052 g•cm −3 . All these data fulfilled the minimum requirements for authentic apple juices given in the Code of Practice of European Fruit Juice Association, which are 1.045 g•cm −3 for juice from concentrate and 1.040 g•cm −3 for direct juices [33].…”

A Method of Evaluating Apple Juice Adulteration with Sucrose Based on Its Electrical Properties and RCC Model

“…In this context, it is justified to continue research on juice adulteration using modern instrumental methods, including the electrical methods that are inexpensive, rapid, and simple to perform and effective in terms of sensitivity, repeatability, and non-invasiveness. The measurements of conductivity parameters-impedance and admittance-were performed assuming that the conductivity properties are an approximate measure of the relative number, type, and concentration of free electric charges present in juice and that the electric field generated between two electrodes can be used to determine their ability to conduct electric current in an electrolyte solution [22,24,46].…”

“…The methods for testing electrical properties, developed based on such electrical parameters as impedance, conductivity, capacitance, and dielectric constant, have gained in significance in recent years. They are employed to assess changes in the degree of fruit ripeness, damage, and spoilage [16][17][18]; determine contents of sugar, water, TSS, minerals, dry matter, and pH value; and to detect bacteria and impurities harmful to human health in fruits and fruit juices [6,15,[19][20][21][22][23][24], among other applications. According to Muñoz-Huerta et al [25], a reliable alternative to the conventional non-destructive techniques can be offered by electrical methods, including electrochemical impedance spectroscopy (EIS), which can provide information about the properties (structure, chemical composition) and behavior of the tested sample in the electric field [26,27].…”