Non-invasive, objective measurement of intramuscular fat in beef through ultrasonic A-mode and frequency analysis

Abstract

A noninvasive, objective measurement method for predicting intramuscular fat concentration in beef through ultrasonic A-mode and frequency analysis was developed. Ultrasonic longitudinal and shear speed were evaluated for the estimation of intramuscular fat in the time domain. Ultrasonic attenuation in beef muscle also was measured through the amplitude ratio method in the time domain and frequency shift method in the frequency domain. Moisture content in beef could be predicted using ultrasonic parameters both in the time and in the frequency domain, noninvasively. Ultrasonic frequency analysis provided the most important parameters for intramuscular fat prediction. In fact, the number of local maxima, which is multiple peak of Fourier spectrum of ultrasonic signal, using the 2.25 MHz shear probe was the most significant parameter for predicting intramuscular fat concentration in the frequency domain. Empirical models were developed to predict intramuscular fat concentration from ultrasonic parameters both in the time and in the frequency domain. A nonlinear regression model was developed based on longitudinal speed in the time domain; whereas, a multivariate regression model, including lower frequency, bandwidth, and local maxima as input variables, was developed for intramuscular fat concentration prediction in the frequency domain. As a result of validating these regression models using the cross-validation method, the nonlinear model in the time domain was capable of predicting intramuscular fat concentration with 1.36 percentage fat error (P <.001) and a 1.17 percentage fat error (P < .05) occurred when predicting intramuscular fat through the multilinear model in the frequency domain..