Ultrasound versus convection cooking of beef longissimus and pectoralis muscles

Longissimus and pectoralis muscles were removed from 10 steer carcasses at 4 days postmortem , aged for 14 days at 4 ÌŠF, then assigned to either ultrasound (ULS) or convection (Conv) cooking to either 144 or 15 8 ÌŠF internal temperature. Ultrasound cooking was faster (P<.05), had greater (P<.05) moisture retention and less (P<.05) cooking loss, and used less energy (P<.05). It also produced muscle samples that required less (P<.05) peak force to shear than those from Conv cooking and resulted in superior (P<.05) myofibrillar tenderness. No significant interactions occurred among cooking method, muscle, or endpoint temperature. As expected, longissimus (ribeye) muscles cooked faster (P< .05) and required less (P<.05) energy and were superior (P<.05) in instrumentally measured texture and sensory tenderness than pectoralis muscles. Cooking to 158EF caused greater (P<.05) moisture and cooking losses, required more (P<.05) time and energy, and degraded (P<.05) instrumental textural and sensor y characteristics. Ultrasound offers a new cooking mode that could increase cooking speed, improve energy efficiency and improve some textural characteristics, compared to conventional cooking.


Summary
Longissimu s and pectoralis muscles were removed from 10 steer carcasses at 4 days postmortem , aged for 14 days at 4EF, then assigned to either ultrasound (ULS) or convection (Conv) cooking to either 144 or 15 8 EF interna l temperature.Ultrasound cooking was faster (P<.05), had greater (P<.05) moisture retentio n and less (P<.05) cooking loss, and used less energy (P<.05).It also produced muscle s amples that required less (P<.05) peak force to shear than those from Conv cooking and resulted in superior (P<.05) myofibrillar tenderness.No significan t interactions occurred among cooking method, muscle, or endpoint temperature.As exp ected, longissimus (ribeye) muscles cooked faster (P< . 05) and required less (P<.05) energy and were superior (P<.05) in instrumentall y measured texture and sensory tenderness th an pectoralis muscles.Cooking to 158EF caused greater (P<.05) moisture and cooking losses, re quired more (P<.05)time and energy , and degraded (P<.05) instrumental textural and sensor y characteristics.Ultrasound offers a new cooking mode that could increase cookin g speed, improve energy efficiency and improv e some textural characteristics, compared to conventional cooking.

Introduction
Although numerous techniques have been used to cook meat, variability i n cooking time, energy consumption, and palatability provide obstacle s for universal use of any single technique .Microwave cooking provides fast heating and superior energy efficiency, but lower cooking yields and less tender and flavorful meat than conventional techniques.Ultrasound (ULS) also can heat muscle, and apparatuse s have been developed for ULS cooking of foods and tenderizing meat.Our objec tive was to compare the effects of ULS and convection cooking to two endpoint temperature s on cooking characteristics and textural and sensory properties of a beef locomotion (pec t oralis) and a support (longissimus) muscle.

Experimental Procedures
Deep pectoralis (brisket) and longissimus thoracic (rib cut) muscles were removed from the right sides of 10 Select and Choice steer carcasses at 4 days postmortem, vacuum packaged, and aged at 4EF for a total of 14 days.After aging, muscles were sliced into .4×3.0×3.0 in.sections an d individually vacuum packaged; and muscles within each carcass were assigned randomly to treatments.Treatment s were arranged in 2×2×2 factorial design with two cooking method s (high intensity ultrasoun d or Farberware® "Open Hearth" electric convection broiler), two muscle types (deep pectoralis and longissimus thoracic), and two internal endpoints ( 144 and 15 8EF) as main effects.The ULS cooking w a s accomplished by placing single, unpackaged, meat sections into a water-filled chamber and applying an ultrasonic field using a Tekmar® Sonic Disrupter, operating at 20 kHz and 1000 W. Convection (Conv ) cooking was performed with a Farberware electric broil er.A utility watt meter was connected to both instruments to monitor energy use during cooking and preheating (Conv only).After cooking, muscles were evaluated for Lee-Kramer shear force using an Instron® Universal Testing Machine.Before shearing, cooked meat pieces were cooled to room temperature and weighed to determine cooking losses and to standardize shear force values to a per-gram-of-meat-sheared basis.Peak force (kg /kg sample) and peak force work were determined by shearing perpendicular to the muscle fiber o rientation.Flavor and texture were evaluated by trained sensory panelists.Analysis of variance was used to determine treatmen t effects for this 2×2×2 factorial, randomized , complete block, experimental design.Because no interactions occurred, only main effect means are presented.

Results and Discussion
Becaus e of greater (P<.05) moisture retention (Table 1), ULS cooking resulted in a 60% advantage (P<.05) in cookin g yield.Cooking time was nearly double ( P<.05) for Conv vs. ULS cooking and required nearly twice the energy (P<.05).Becaus e Conv cooking also required preheating, it was even less efficient (P<.05) when total energy use was considered.Ultrasoun d cooks efficiently because energy is directed to th e muscle being cooked, and less is lost to the environment .Also, ULS cooking is uniform because the intense agitation of the liquid medi um by sound wave pressures results in an even distribution of heat.
Cooking loss percentage (T a ble 1), after adjustment for sample weight, did not vary (P>.05 ) between muscle types.Longissimus muscle s require d less (P<.05) cooking time on a cooked, weight-constant basis.Cooking to 144EF internal temperature resulted in less (P<.05) cooking loss, more (P<.05)retained moisture, less (P<.05) cooking time, and, thus, less total energy than cooking to 15 8 EF.No difference (P>.05) was observed between ULS and Conv treatments for peak force to shear samples, when adjusted to per-gram-of-muscle basis (Table 2).However , peak force work was lower (P<.05) for the ULS-cooked samples, which may have been related to the higher (P<.05 ) postcooking moisture content.As expected , pectoralis muscle required more (P<.05)peak force and peak force work to shear than longissimus muscles (Table 2) because of the higher (P<.05) content of connective tissue (Table 1).Muscles cooked to 158EF required more (P<.05)peak force to shear than samples cooked to 14 4EF; however, no difference (P>.05) was observed in peakforce work to shear (Table 2).
Sensory panelists detecte d more charbroiled and beef flavor with Conv cooking (Table 2), probab ly because of the dry heat.Moist heat ULS cooking not only inhibited development of charbroiled flavor, but also may have extracted beef flavor components into th e discarded liquid medium .Greater moisture retention (Table 1) also might have diluted the natural flavor compounds.Although ULS-cooked muscles contained more postcooking moisture, no difference (P>.05) occurred in sensory juiciness between cooking methods.However, sensory panelist s indicated more tender (P<.05) myofibrils with ULS cooking.Connective tissue amoun t and overall tenderness scores were unaffected (P>.05) by cooking method.
Cooked pector alis and longissimus muscles had similar (P> .05) charbroiled flavor intensity, beef flavor intensity, and juiciness (Table 2).However, sensory panelists fou n d that pectoralis muscles had less (P<.05) myofibrillar tendernes s (slightly tender), connective tissue amount (moderate), and overall tenderness (slightl y tough) than longissimus muscles.Charbroiled flavor and beef flavor intensity did not differ (P>.05) between the 144 and 15 8 EF treatments (Table 2).Sensory panelists rated the 144EF treatment more (P<.05)juicy and having more (P<.05)myofibrill a r tenderness but found no difference (P>.05 ) in either connective tissue amount or overall tenderness.
Because sensory properties were not impacted severely, ULS may h a ve advantages in speed and energy efficiency for commercial cooking or precooking.Possible uses of ULS include moist heat precooking or cooking of meat cuts destined for prepared meals.Liquid media such as gravies, sauces, o r soups would be ideal for coupling UL S energy with the meat.Liquid media also would enhance meat textural characteristics and cooked product yields, especially for lower quality cuts containing more connective tissue.Other possible ULS application s might be as in-home cooking devices .Ultrasound would allow convenient, rapid, meal preparation without detrimental effects on meat texture.

s Day 1997 ULTRASOUND VERSUS CONVECTION COOKING OF BEEF LONGISSIMUS AND PECTORALIS MUSCLES F. W. Pohlman , M. E. Dikeman 1 J. F. Zayas , and J.A. Unruh 2
Pettis 1 Rd., St. Joseph, MO 64503.Deceased.Formerly a faculty member in the Department of Foods and Nutrition.211Cattlemen'

Table 1 . Effects of Cooking Method, Muscle, and Endpoint Temperature on Beef Muscle Cooking Characteristics and Energy Consumption
c Energy consumed during preheating mode.dEnergy consumed during cooking mode.eEnergy consumed during cooking plus preheating modes.f

Table 2 . Effects of Cooking Method, Muscle, and Endpoint Temperature on Instrumental Textural Properties and Sensory Panel Evaluations
Means within cooking method, muscle, or endpo i nt temperature bearing different superscript letters differ (P<.05).