Mechanisms of Crust Development at the Surface of Beef Meat Subjected to Hot Air: An Experimental Study

Effects of different curing concentrations and drying times on the microbial community structure and metabolites of dried Spanish mackerel

Cured Spanish mackerel has a promising market owing to its nutritious nature as well as ease of transportation and preservation. However, the nutritional and flavor formation mechanism of Spanish mackerel after curing and drying is unclear. To overcome this problem, the effects of different processing conditions on the free amino acid, microbial community, and flavor of Spanish mackerel were explored. Staphylococcus and Cobetia are the main microorganisms in cured mackerel and are closely associated with the formation of their quality. Compared with fresh mackerel, cured mackerel contains increased levels of protein, fat, and chloride, contributing to its distinctive flavor. The contents of free amino acids in the BA64 group were substantially higher than those in other groups, particularly the contents of threonine, glycine, and tyrosine. These findings will contribute to the development of high-quality cured Spanish mackerel products and cured aquatic products.

Trained sensory descriptors and volatile aroma compounds of USDA Select steaks using five grill temperatures

Thirty-three USDA Select boneless top loins were selected from carcasses at a commercial major packing plant, vacuum-packaged, and aged for 14 d (4 °C). The loins were then divided into 10 portions (5 grill temperatures for each of trained sensory panel and Warner-Bratzler shear force). Flat-top electric grills were pre-heated to 1 of 5 different temperatures: 149 °C (149), 177 °C (177), 204 °C (204), 232 °C (232), or 260 °C (260). Steaks were placed on the grill, turned when the internal temperature reached 35 °C and removed when the internal temperature reached 71 °C. A trained sensory panel evaluated ten basic flavors and five texture attributes. Extra cubes from each sample were frozen in liquid nitrogen and stored at -80 °C for GC/MS volatile aroma compound analysis. Beef identity, brown, and roasted flavor descriptors increased linearly (P < 0.001) while bloody/serumy tended to decrease (P = 0.016) and sour flavor decreased (P = 0.006) linearly as grill temperature increased. Furthermore, burnt (deviation P = 0.008) and bitter (deviation P = 0.012) flavor descriptors were affected by effects other than linear or quadratic, while umami (P = 0.002) and overall sweet (P = 0.016) flavors increased quadratically from 149 to 232 then declined at 260 grill temperatures. Two alcohols, eight aldehydes, four alkanes, three furans, eight ketones, and twelve pyrazines were impacted by differences the grill temperature. Increasing grill temperature increases volatile compounds, primarily from the Maillard reaction, that improve positive beef flavor descriptors.

MRI-computer vision on fresh and frozen-thawed beef: Optimization of methodology for classification and quality prediction

This study aims to evaluate the capability of Magnetic Resonance Imaging (MRI) and computer vision techniques to classify fresh (raw F) (n = 12) and frozen-thawed (FT) (n = 12) beef and predict physico-chemical, texture and sensory characteristics by optimization the methodology for image analysis (algorithm) and data analysis (regressor), testing different algorithm-regressor combinations. The accuracy of the classification and prediction results especially depend on the algorithm. Different optimum combinations were found for classification (Fractal with CForest, RF or SVM) and prediction of quality parameters of raw FT (Fractal-CForest or Fractal-RF) and cooked FT samples (Classic-RF). Thus, the computational analysis of MRI, especially the algorithm to analyze the image, may be set as a function of the aim (classification or prediction) and of the type of sample (raw or cooked), while the analysed characteristic is not relevant. This study firstly showed the capability of MRI to classify beef (raw F vs. raw FT) and to determine quality characteristics in a non-destructive way.

Optimization of the image acquisition procedure in low-field MRI for non-destructive analysis of loin using predictive models

The use of low-field magnetic resonance imaging (LF-MRI) scanners has increased in recent years. The low economic cost in comparison to high-field (HF-MRI) scanners and the ease of maintenance make this type of scanner the best choice for nonmedical purposes. However, LF-MRI scanners produce low-quality images, which encourages the identification of optimization procedures to generate the best possible images. In this paper, optimization of the image acquisition procedure for an LF-MRI scanner is presented, and predictive models are developed. The MRI acquisition procedure was optimized to determine the physicochemical characteristics of pork loin in a nondestructive way using MRI, feature extraction algorithms and data processing methods. The most critical parameters (relaxation times, repetition time, and echo time) of the LF-MRI scanner were optimized, presenting a procedure that could be easily reproduced in other environments or for other purposes. In addition, two feature extraction algorithms (gray level co-occurrence matrix (GLCM) and one point fractal texture algorithm (OPFTA)) were evaluated. The optimization procedure was validated by using several evaluation metrics, achieving reliable and accurate results (r > 0.85; weighted absolute percentage error (WAPE) lower than 0.1%; root mean square error of prediction (RMSEP) lower than 0.1%; true standard deviation (TSTD) lower than 2; and mean absolute error (MAE) lower than 2). These results support the high degree of feasibility and accuracy of the optimized procedure of LF-MRI acquisition. No other papers present a procedure to optimize the image acquisition process in LF-MRI. Eventually, the optimization procedure could be applied to other LF-MRI systems.

Detection of p-Nitroaniline Released from Degradation of 4,4'-Dinitrocarbanilide in Chicken Breast during Thermal Processing

The diphenylurea 4,4'-dinitrocarbanilide (DNC) is the residue of concern left in edible tissues of broilers fed diets containing the anticoccidial nicarbazin. When chicken meat is submitted to thermal processing, p-nitroaniline (p-NA) is expected from DNC degradation. This work aimed at evaluating whether thermal processing of DNC-containing chicken meat induces p-NA appearance. First, a hydrolysis assay was performed in aqueous solutions at 100 °C in different pH, confirming that DNC cleavage yields p-NA. Then a novel LC-MS/MS method was used to detect traces of this aromatic amine in DNC-containing chicken breast fillets subjected to cooking methods. Our evidence showed p-NA occurrence in such chicken meat samples, which corroborated results from hydrolysis assay. The p-NA appearance in fillets was rather discrete during boiling treatment, but its concentration became pronounced over time for grilling, frying, and roasting, achieving respectively 326.3, 640.0, and 456.9 μg/kg. As far as we are concerned, no other research identified degradation products from DNC residue in heat-processed chicken fillets. Therefore, this study leads to additional approaches to assess impacts on food safety.

Grilling temperature effects on tenderness, juiciness, flavor and volatile aroma compounds of aged ribeye, strip loin, and top sirloin steaks

Ribeye, top loin, and top sirloin steaks were assigned a grilling temperature setting (177°C, 205°C, or 232°C) and consumer panel, Warner-Bratzler shear force, trained sensory panel, and GC/MS - olfactory analyses were performed. No differences (P > 0.05) in consumer overall, tenderness, juiciness, appearance, and flavor liking were detected among steak type or grill temperature. Grill surface temperature had no effect (P > 0.05) on trained panel tenderness scores. Of the volatiles present during an aroma event, pyrazine compounds were most influenced by grill surface temperature. The tenderness and juiciness of steaks grilled at differing temperatures were not perceived to be different by consumers; however, grilling temperature impacted the flavor of the final product by generating more pyrazine compounds. Steaks in this study likely were too tender to have a grilling effect on tenderness, but selecting different grilling temperatures can be used to vary the amount of browning of steaks and/or to modify aroma volatile compounds.

Determination of volatile aroma compounds in beef using differences in steak thickness and cook surface temperature

Top loin steaks with a United States Department of Agriculture (USDA) grade of Select were cut 1.3cm, 2.5cm, or 3.8cm thick and cooked on a skillet at 177°C, 204°C, or 232°C. Aroma compounds described as fatty, tallow, and oily are highly related to the identity of beef flavor. These compounds are produced in the highest quantity when steaks are cooked either at low temperatures (177°C) or for short periods of time. Whereas, aroma compounds described as roasted, nutty, or fruity are developed from browning the surface of the steak as a result of cooking at high skillet surface temperatures (232°C) or for long periods of time, as would be seen cooking thick steaks (3.8cm). This study shows that the amount of specific aroma compounds can be predicted (r(2) values up to 0.62) from measured cooking times and temperatures. It may be possible to develop beef steak flavor by recommending steak thickness and cooking temperatures.