Michael Ngadi

Prediction of drip-loss, pH, and color for pork using a hyperspectral imaging technique.

Many subjective grading methods with poor repeatability and tedious procedures are still widely used in meat industry. In this study, a hyperspectral-imaging-based technique was investigated to evaluate its potentials for objective determination of pork quality attributes. The system extracted spectral and spatial characteristics simultaneously to determinate the quality attributes, drip loss, pH, and color, of pork meat. Six feature band images were selected for predicting the drip loss (459, 618, 655, 685, 755 and 953nm), pH (494, 571,637, 669, 703 and 978nm) and color (434, 494, 561, 637, 669 and 703nm), respectively. Two intensity indices of the band images were used as inputs to establish neural network models to predict the quality attributes. The results showed that with the hyperspectral-imaging system, the drip loss, pH, and color of pork meat could be predicted with correlation coefficients of 0.77, 0.55 and 0.86, respectively. Pork meat could be classified based on their exudative characteristics and color successfully.

Recent Developments in Hyperspectral Imaging for Assessment of Food Quality and Safety

Hyperspectral imaging which combines imaging and spectroscopic technology is rapidly gaining ground as a non-destructive, real-time detection tool for food quality and safety assessment. Hyperspectral imaging could be used to simultaneously obtain large amounts of spatial and spectral information on the objects being studied. This paper provides a comprehensive review on the recent development of hyperspectral imaging applications in food and food products. The potential and future work of hyperspectral imaging for food quality and safety control is also discussed.

Electrohydrodynamic Drying—A Concise Overview

Electrohydrodynamic (EHD) drying is a novel method of non-thermal processing. The drying can be carried out using either AC or DC high voltages. The thermodynamic considerations regarding the lowering of temperature under EHD drying include rapid rates of evaporation and exothermic interaction of the electric field with a dielectric material. Multi-point and plate electrode systems are efficient in accelerating drying of agricultural materials. Compared to hot air (convective) drying systems, EHD drying systems offer lower food production costs along with superior quality in terms of physiochemical properties such as color, shrinkage, flavor, and nutrient content. Compared to convective and freeze-drying, EHD drying systems, given their simpler design and lesser energy consumption, show great potential for bulk and industrial drying applications.

Effect of Pretreatments on Drying Characteristics of Okra

This study was conducted to evaluate the effect of different pretreatment methods (blanching, microwave, and pulsed electric field [PEF]) on drying and rehydration behavior of okra. Drying rates were significantly (P < 0.05) influenced by the different pretreatments. The control samples had the lowest coefficient of diffusivity while samples pretreated with PEF at maximum energy input (4 kV/cm, 500 nF) had the highest coefficient. A simple exponential model used for describing the drying behavior of okra gave moisture diffusivity values ranging between 4.56 × 10−10 and 8.05 × 10−10 m2/s and the coefficient of determination values were between 0.94 and 0.98. Rehydration capacities of the control and pretreated samples were significantly different.

Binding of curcumin to β-lactoglobulin and its effect on antioxidant characteristics of curcumin

The binding of curcumin (CCM) to bovine β-lactoglobulin (β-Lg) was investigated by Fourier transform infrared and fluorescence. The effect of binding on antioxidant activity of CCM was determined by using ABTS and hydroxyl radical scavenging capacity and total reducing ability. Our results showed that when CCM binds to β-Lg, it lead to a partial change in protein structure. In fact, CCM was bound respectively to two different sites of protein at pH 6.0 and 7.0 via hydrophobic interaction. CCM-β-Lg complex was formed by one molecule of protein combining with one molecule of CCM. Moreover, the average distance from one binding site to Trp residues in protein is similar with another. This result suggested that fluorescence resonance energy transfer cannot be used as unique method to study the characteristics of binding of ligands to proteins. The antioxidant activity of CCM might be improved by binding with β-Lg.

Impact of Pulsed Electric Fields on the Dehydration and Physical Properties of Apple and Potato Slices

Abstract The effect of pulsed electric fields (PEF) on drying and some physical properties of apple and potato was evaluated. Pulsed electric field intensities from 0.75 to 1.5 kV/cm with pulse duration within 100 and 300 μs were studied. The number of pulses applied was up to 120. Measurement of porosity and density were conducted using a mercury porosimeter. The drying process was carried out in a convective air oven at 70°C. The compressive strength of apples was reduced between 21 and 47% after treatment. The results show potential advantage for PEF enhanced juice extraction from the tissues even at moderate PEF treatment. PEF treatment increased porosity and particle density but decreased bulk density. Treating the apple samples with PEF resulted in generation of more pores of sizes in the order of cell wall thickness. Thus electric field application affected not only cell membranes but also cell wall integrity. PEF treatment enhanced drying rates of potato samples. Diffusion coefficients of PEF pretreated potato samples increased by up to 40%.

Inactivation of Escherichia Coli O157:H7 in Liquid Dialyzed Egg Using Pulsed Electric Fields

Pulsed electric field (PEF) pasteurization may be used either to replace or supplement conventional processing of heat-sensitive products such as liquid egg. The objective of this study was to investigate inactivation characteristics of Escherichia coli O157:H7 in liquid egg products at low temperature using square waveform pulsed electric fields. Dialyzed liquid egg products, namely whole egg, egg white and egg yolk, were exposed to an electric field of lSkVcm −1 at a low temperature of 0°C. The square voltage fields were generated across parallel plate treatment chambers. A pulse frequency of 1 Hz was used. Up to 500 pulses were applied. Product temperature during the PEF treatment was controlled using a water cooling system. About 1, 3 and 3.5 log reductions were obtained for the dialyzed egg white, egg yolk and whole egg products, respectively. The results showed that microbial inactivation rate increased with increasing number of pulses, especially for the egg yolk and whole egg products. The inactivation kinetics was exponential with some tailing. A new kinetic model for the bacteria inactivation was proposed.

Rheological Characteristics of Arabic Gum in Combination With Guar and Xanthan Gum Using Response Surface Methodology: Effect of Temperature and Concentration

A rheological characterization of combination guar and xanthan gum with 20 kg/100 kg sample arabic gum was performed at 20 to 80°C by the application of the response surface methodology using an advanced controlled rate rheometer. The guar and xanthan gum concentrations employed were 0.25-1.25 kg/100 kg sample. The flow of both combinations was adequately described by Herschel-Bulkley model over the shear rate range of 0-500 s−1. The combination of arabic-guar exhibited shear-thinning behavior while arabic-xanthan combination behaved as a dilatants fluid with yield stress. A quadratic model developed for rheological parameters met all the criteria of good fit and provided useful information. It was observed that temperature and concentration affected yield stress, consistency coefficient and apparent viscosity (P<0.05) of gum combinations however, flow behavior index did not. The concentration of gum significantly (P<0.05) affected all the rheological parameters and temperature was the least. Addition of arabic gum significantly (P<0.05) reduced rheological properties of both guar and xanthan gum.

Pork Quality Classification Using a Hyperspectral Imaging System and Neural Network

Pork quality is usually determined subjectively as PSE, PFN, RFN, RSE and DFD based on color, texture and exudation of the meat. In this study, a hyperspectral-imaging-based technique was developed to achieve rapid, accurate and objective assessment of pork quality. The principal component analysis (PCA) and stepwise operation methods were used to select feature waveband from the entire spectral wavelengths (430 to 980 nm). Then the feature waveband images were extracted at the selected feature wavebands from raw hyperspectral images, and the average reflectance (R) was calculated within the whole loin-eye area. Artificial neural network was used to classify these groups. Results showed that PCA analysis had a better performance than that of stepwise operation for feature waveband images selection. The 1st derivative data gave a better result than that of mean reflectance spectra data. The best classified result was 87.5% correction. The error frequency showed that RSE samples were easier to classify. The PFN and PSE samples were difficult to separate from each other.

Electrical Conductivities of Liquid Egg Products and Fruit Juices Exposed to High Pulsed Electric Fields

Electrical conductivity can be used to monitor important changes in a food product during pulsed electric field (PEF) processing. Electrical conductivities of selected fruit juices (namely apple, orange, and pineapple juices) and liquid egg products (namely whole egg, yolk, and egg white) were determined online during a PEF treatment. The property was measured at broad processing temperatures ranging from 5 to 55°C. Electrical conductivity increased linearly with increasing temperatures for all the products. The liquid egg products have the highest overall electrical conductivity varying from 0.22 to 1.1 S/m whereas fruit juice products have the lowest electrical conductivity ranging from 0.13 to 0.63 S/m. Regression equations of electrical conductivity as functions of temperature were developed. This paper provides a database and equation correlations of food electrical conductivity that could be used to design and optimize PEF process.