Food and Nutrition Sciences, 2013, 4, 38-42 http://dx.doi.org/10.4236/fns.2013.49A2006 Published Online September 2013 (http://www.scirp.org/journal/fns) Sensing the Moisture Content of Dry Cherries—A Rapid and Nondestructive Method Chari Venkatkrishna Kandala 1* , Ramesh Avula 2 , Vijayasaradhi Settaluri 3 , Ronda Srinivasa Reddy 3 , Naveen Puppala 4 1 United States Department of Agriculture, Dawson, USA; 2 R&D, Cherry Central, Traverse City, USA; 3 Department of Biotechnol- ogy, K.L. University, Vaddeswaram, India; 4 New Mexico State University, Clovis, USA. Email: * chari.kandala@ars.usda.gov Received July 15 th , 2013; revised August 15 th , 2013; accepted August 22 nd , 2013 Copyright © 2013 Chari Venkatkrishna Kandala et al. This is an open access article distributed under the Creative Commons Attri- bution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT Impedance (Z), and phase angle (θ) of a parallel-plate capacitor with a single cherry fruit between the plates were mea- sured using a CI meter (Chari’s Impedance meter), at 1 and 9 MHz. Capacitance C was derived from Z and θ, and by using the C, θ, and Z values of a set of cherries whose moisture content (MC) values were later determined by the hot air-oven method, a calibration equation was developed. Using this equation, and their measured C, θ, and Z values, the MC of a group of cherries, not used in the calibration, was predicted. The predicted values were compared with their vacuum-oven values. The method worked well with an R 2 value of 0.98 and a standard error of prediction (SEP) of 1.24, in the measured moisture range between 5% and 20%. Keywords: Cherries; Moisture Content; Capacitance; Impedance; Phase Angle; Regression; CI Meter 1. Introduction The United States is the second-largest producer of cher- ries in the world, right behind Turkey, the leading pro- ducer. Cherries are of two varieties, prunusavium L, the sweet one, and prunuscerasus L, the tart one. The later variety is predominantly grown in the state of Michigan. Cherries are highly perishable, and to preserve them for longer periods, they are subjected to drying to decrease their moisture content to a safe level [1]. Dried cherries have a much longer shelf life, and are available to the consumer, at any time during the year [2]. However, dried fruits are also susceptible to damage by microor- ganisms as in the case of cereals and nuts. High mois- tures are known to be conducive to such damages that leave the fruits unfit for human consumption. Drying the fruit was found to have a minimal effect on its nutri- tional value, and have the advantage of occupying less storage place than the fresh fruit. Drying of cherries is usually done by atmospheric forced-air driers, by passing hot air over them at controlled relative humidity, till they dry to the required MC value. During the process the MC has to be measured repeatedly to ensure that the heating is stopped when the required moisture value is obtained. Over-heating could increase the drying costs, and adver- sely affect the quality of the fruit. Presently available methods for moisture determination in fruits such as cherries are the standard vacuum-oven method [3] and the Karl Fisher titration method [4]. In the vacuum-oven method, the MC is determined by heating the samples in a vacuum-oven at 70˚C till a constant weight is obtained. The method is time-consuming and destructive. In the Karl Fisher method, the fruit is ground to a pulp and used in the titration. This method is also time-consuming and destructive. Thus, a method which is rapid and nonde- structive would be of great use in the fruit industry to measure the MC content repeatedly, and without sample preparation or destroying the sample. In this work, an electrical method is described that would be suitable for cherries and similar fruits. 2. Basic Principles Previous research showed that the variation in dielectric constant with MC for shelled yellow field-corn was more pronounced between 1 and 5 MHz [5]. Thus, (ε r1 − ε r2 ), the difference in the dielectric constants at 1 and 5 MHz * Corresponding author. Copyright © 2013 SciRes. FNS