Tenderness is the most important textural attribute of meat and one of the biggest attributes that influences a consumer's acceptance of a meat product^1,2. Given the high variability of tenderness among beef muscles^3,4, the consistent supply of tender beef is an ongoing challenge for the beef industry⁵. In order to attain market share for traditionally tougher beef cuts, technologies such as blade tenderization and marination have been developed to improve tenderness of beef products. Marinating, or enhancing, is the process of adding non-meat ingredients to fresh meat to improve eating quality by through increased tenderness, juiciness, and flavor⁶. Results from the U.S.A. National Meat Case Study conducted in 2004 showed that 15.8 % of the whole muscle beef products in the retail cases surveyed were enhanced⁷.

Beef fajitas are an extremely popular dish in Mexico, causing significant demand for both the inside (M. transversus abdominus) and outside skirt (M. diaphragma pars costalis)⁸. Due to the significant demand for skirt steaks, many entities are looking for other thin muscle alternatives that possess similar eating characteristics and can be used as a substitute for skirt steaks. One of these alternatives is rose meat (Cutaneous trunci). Use of rose meat in this application would benefit the beef industry, as this cut is less than acceptable in ground beef applications due to low pigment (myoglobin) concentrations. Numerous studies have been conducted to review certain characteristics of the skirt steak and rose meat^8-11However, few of these studies have examined all sensory attributes of these cuts, especially as both a non-marinated and marinated product^8,12. The objective of this study was to evaluate the characteristics of NM and MR rose meat according to its country of origin (U.S.A. vs Mexico). The inside skirt was chosen as the benchmark as it is widely used in Mexico, is commonly utilized as a marinated product, and would be used in similar foodservice applications as rose meat.

Rose meat was sourced from major packers in the U.S. and Mexico. Rose meat arrived in vacuum packaged bags that contained two to three pieces if it was of U.S. origin or four to six pieces if it was of Mexican origin. Each piece was identified and weighed. Whole-pieces were cut into approximately eight 10 cm long by 2.5 cm thick samples. Samples were weighed, trimmed relatively free of fat and then weighed again to determine an initial rough weight for each sample. Approximately four samples from each larger piece were randomly assigned to either the marinated or non-marinated treatment. Following fabrication, all samples were vacuum packaged and frozen until further processing.

Rose meat and inside skirts were marinated by immersing meat in a solution that contained sodium tripolyphosphate, carrageenan, xanthan gum, sodium benzoate and sodium erythorbate dissolved in water at a rate of 1 kg of marinade ingredients per 20 L of water. Twenty liters of marinade were used for every 100 kg of meat in the tumbler. Vacuum was applied for the first five minutes of tumbling, followed by an additional 20 min of tumbling during which no vacuum was applied.

Warner-Bratzler shear force was conducted according to the American Meat Science Association (AMSA) Research Guidelines for Cookery, Sensory Evaluation and Instrumental Tenderness Measurements of Fresh Meat¹³. All samples were cooked to an internal temperature 70 °C regardless of cookery method (grilling or braising). For analysis with the grilling method, steaks were cooked on open-hearth grills. Temperature was monitored using iron-constantan thermocouples on a portable recording thermometer (Omega Engineering Inc., Stamford, CT, USA). Steaks were flipped when they reached 35 °C and allowed to cook until reaching 70 °C. Analysis via moist heat cookery (braising) was conducted using oven set at a 150 °C that had a pan of water placed in the bottom. Steaks were cooked in the oven for 35 min to the same degree of doneness to those steaks that were grilled (70 °C). Following cooking, steaks were allowed to equilibrate to the ambient room temperature of approximately 20 to 25 °C. A minimum of eight cores (2.54 cm thick and 1.27 cm diameter) were removed from each steak parallel to the muscle fibers. Cores were sheared perpendicular to the muscle fiber using a digital Warner-Bratzler shearing device. Average Warner-Bratzler shear force (WBSF) value of each sample was recorded. Cook loss (percent) was calculated by taking initial weight of the sample minus the cooked weight and dividing by initial weight.

A total of 141 consumers were recruited from the National Autonomic University of Mexico in Mexico City, Mexico. Panelists were faculty and students who were regular beef eaters. Each treatment (marinated and non-marinated rose meat/outside skirt from the U.S. or Mexico) was evaluated by each panelist. Steaks were cooked using the moist heat cookery method described above. The edges of cooked steaks were trimmed and the lean meat portion was cut into cubes approximately 2 cm on each side. Each panelist received four samples served on a disposable plastic plate. Samples were assigned random numbers and presented simultaneously to panelists such that all treatment comparisons were represented on each tray. Responses for aroma, juiciness, flavor, texture, and overall acceptability were marked on a seven-point hedonic scale (1= I dislike it very much and 7= I like it very much).

Plots of residuals and the W-statistic¹⁴ were evaluated to determine homogeneity of variance and normality for Warner-Bratzler shear force (WBSF) values and cook loss. Denominator degrees of freedom were calculated using the Kenward-Roger approximation¹⁵ and means were separated using pairwise t-tests and a significance level of 0.05. SAS 9.3¹⁶ was used for all analysis. Mixed models were analyzed using the MIXED procedure. Models for WBSF and cook loss by cut included the fixed effects of country of origin, marinade and cookery method, and the random effect of trial.

Differences in WBSF by cut type included the fixed effects of cut type, marinade and cookery method, and the random effect of trial. All interactions were assessed and included in models if found to be significant (P<0.05). Cook time was assessed as a covariate and subsequently removed from models, as it was not able to account for a significant amount of variance in WBSF or cook loss (P>0.05). The effect of country-of-origin on rose meat characteristics (cook loss, tenderness, sensory attributes) was assessed using models that contained the fixed effect of country-of-origin and the random effect of the piece from which samples were derived. Trim loss was assessed as a potential covariate for weight gain following marination, but was found to be non-significant in all models (P>0.05).

The interaction between marinade and country of origin influenced WBSF values of rose meat (P<0.05), consequently main effects were unable to be determined (Table 1). Similarly, the interaction between cookery and marinade influenced WBSF values of skirt steaks (P<0.05). Marinating enhances tenderness and juiciness while also increasing product yield⁶. Salt is used in marinades to improve the flavor and increase the uniformity of distribution of the solution throughout the product. Phosphates interact with the proteins and increase their ability to hold moisture during cooking, resulting in increased juiciness in cooked beef⁶. Improved tenderness following application of marinade has been reported by previous works^17,18 and appeared to influence WBSF of rose meat from Mexico in this study; however, this effect was not seen in rose meat from the U.S.

After marination, rose meat had an average weight increase of 10 ± 3 % and inside skirts had an average increase of 38 ± 2 %. The uptake of marinade by these cuts has potentially huge financial implications to further processors, while also dramatically influencing the nutritional content of finished products. If marinade is absorbed at this rate in skirt steaks, many finished products will likely have excess levels of sodium, potentially leading to health concerns by consumers. The three ways interaction between cut, cookery method and marinade was influential to cook loss (P<0.05; Figure 1). It has been showed that calcium chloride marinating did not increase cook loss in longissimus lumborum steaks¹⁹. However, other studies have shown that marinating increases cook loss in certain muscle cuts^17,20. This seems to indicate that cook loss due to marination effects may be influenced by muscle type and the solution used. Even with the higher percent of weight increase, marinating the inside skirts did not result in a higher cook loss percentage than the rose meat, regardless of whether the rose meat was marinated or not.

Differences in country-of-origin (Mexico vs U.S.) were partitioned as a random effect. The interaction of cut, cookery method and marinade was significant (P<0.05).

Figure 1 Cook loss of marinated (MAR) or non-marinated (No MAR) rose meat and outside skirt as determined after grilling or braising 

The addition of salt and phosphate increases yield but also indicated that the cooking method had a significant effect on cooking loss. In contrast to grilling, wet-oven cooking losses appeared to be lower²¹; however, this conclusion could not be confirmed due to effect of the three-way interaction. Excluding the NM rose meat from Mexico, all of the oven-cooked cuts exhibited less cook loss than the grilled cuts.

Marinated top round steaks cooked to "medium and less" received lower flavor ratings than marinated steaks cooked to "medium well and more," indicating that consumer acceptability of marinated steaks could vary significantly depending on the degree of doneness, regardless of cooking method²². It has been found that marination improved juiciness sensory scores in seven of eight muscles evaluated¹⁸. The results of the sensory analysis of NM and MR rose meat by consumer panelists are shown in Table 2. The MR rose meat originating from the U.S.A. received the highest sensory scores for aroma, juiciness, flavor, and texture, and overall acceptance. The Mexican NM rose meat consistently received the lowest scores across all of the sensory categories. Marinated rose meat, regardless of country of origen, received significantly higher (P<0.05) sensory scores than the NM samples in all five sensory categories.

Although main effects were unable to be determined in much of this work, application of marinade appeared to improve tenderness of rose meat and moist heat cookery appeared to reduce cook loss. Furthermore, marinated inside skirt appeared to be more tender than rose meat, regardless of country of origin or cookery method. Since the inside skirts used in these analyses were exclusively of U.S. origin, additional research is needed to determine how the tenderness and cook loss of rose meat of U.S. origin compares to the same traits in Mexican inside skirts. Consumer panels indicated that marinated rose meat increased acceptance. The increased moisture retention found in oven-cooked steaks most likely contributes to the decreased shear force found in the marinated rose meat.

From this study is concluded that oven cooking could be a more ideal method for preparing marinated rose meat. Inside skirts appeared tender than rose meat, but favorable sensory scores for marinated rose meat indicate that consumer acceptance could be high, but further research is needed to compare sensory characteristics between marinated inside skirts and rose meat. Alternative applications of rose meat in the beef industry should be evaluated as the product is inferior for ground beef production and offers a tremendous opportunity to add value to each carcass harvested.