Nondestructive Evaluation of Wet Aged Beef by Novel Electrical Indexes: A Preliminary Study

The aim of this study was to investigate the suitability of electrical impedance spectroscopy (EIS) as a nondestructive quality monitoring tool of aged beef, focusing on the development of accurate electrical indexes. The relationship between the electrical indexes derived from the impedance ratio (IR) or admittance was established. Quality parameters such as the drip loss, cooking loss, water-holding capacity, and shear force of beef loin wet-aged for 0 to 21 days were evaluated to develop the new electrical indexes. In addition, the predictive capability of EIS was trialed using different indexes and frequencies. This study revealed that the most appropriate choice is to use electrical parameters at a lower frequency to determine or predict the physical properties of aged beef. The IR was derived from the ratio between the electrical impedance measured parallel to and perpendicular to the muscle fibers in the low-frequency domain. Furthermore, the degradation of muscle fibers was observed by optical microscopy. The investigated electrical indexes had higher correlations with shear force (0.52 ≤ R2 ≤ 0.58) compared to correlations with aging days (0.34 ≤ R2 ≤ 0.39). The findings of the study could be used for meat quality inspection in slaughterhouses as well as during aging.

Structured Illumination Reflectance Imaging for Enhanced Detection of Subsurface Tissue Bruising in Apples

In this research, a structured illumination reflectance imaging (SIRI) system was used as a novel method for detection of fresh bruises on apples. The SIRI system projects sinusoidal patterns of illumination onto samples, and image demodulation is then used to recover depth-specific information through varying the spatial frequency of the illumination pattern. The capability of SIRI was demonstrated through the detection of artificially induced bruises on ‘Golden Delicious’ and ‘Delicious’ apples with varying levels of bruising. It was hypothesized that by confining the light penetration depth near the surface of each fruit, subsurface defects such as bruising should be more apparent under SIRI than conventional planar illumination imaging. Three 120° phase-shifted reflectance images were acquired from 60 fruit each of ‘Golden Delicious’ and ‘Delicious’ varieties at 0 h, 4 to 6 h, and 24 h after impact bruising for each of the four spatial frequencies (i.e., 0, 0.10, 0.15, and 0.25 cycles mm-1). The reflectance images acquired by the system were then demodulated into an alternating component (AC) and direct component (DC), where the AC contained depth-specific information and the DC image represented the diffuse reflectance from the apple sample under uniform (or planar) illumination. Bruise detection algorithms were developed and applied to the demodulated AC and DC images. The SIRI system achieved 70% to 100% bruise detection rates, compared to 0% to 50% detection rates under conventional planar illumination. However, detection results were influenced by both severity of bruising and bruise development after impact; better bruise detection results were obtained when bruises had developed for 4 to 6 h after impact. SIRI has demonstrated a superior capability of detecting fresh bruises, and it is promising as a new imaging modality for quality detection of agricultural products. Keywords: Apples, Bruises, Defects, Fruit, Imaging, Nondestructive, Quality, Sorting, Structured illumination.