Low voltage electrical stimulation of lamb carcasses: eects on meat quality P. Polidori a, *, S. Lee b , R.G. Kauman b , B.B. Marsh b a Facolta Á di Medicina Veterinaria, Universita Á degli Studi di Camerino, Via Circonvallazione 93, 62024 Matelica (MC), Italy b Muscle Biology Laboratory, University of Wisconsin, Linden Drive 1805, 53706 Madison, WI, USA Received 13 January 1999; received in revised form 31 March 1999; accepted 6 April 1999 Abstract The eects of an early post mortem low voltage electrical stimulation (28 V, 60 Hz) on biochemical changes and on ®nal ten- derness in muscles Longissimus thoracis et lumborum and Semimembranosus from lamb carcasses were studied. It was shown that electrical stimulation accelerated the glycolytic process resulting in a signi®cant fall in pH during the ®rst 6 h post mortem in both muscles examined and in a signi®cant reduction in adenosine triphosphate (ATP) content in muscle Longissimus thoracis et lum- borum. The eect of electrical stimulation on tenderness was recorded by measuring shear force values 2 and 7 days post mortem. Tenderness was signi®cantly improved by electrical stimulation for the Longissimus thoracis et lumborum both at 2 and at 7 days post mortem, while for Semimembranosus electrical stimulation signi®cantly increased tenderness just at 7 days post mortem. # 1999 Elsevier Science Ltd. All rights reserved. 1. Introduction Factors aecting muscle tenderness have been exten- sively researched over the past 50 years. Initially, the connective tissue component of meat received the greatest attention (Cross, 1979). Since 1960, the state of muscle contraction following rigor mortis has been the most intensively studied. The discovery that muscle shortening is the major cause of meat toughness has led to the realization that post mortem treatments far out- weigh live-animal factors such as breed, age and pre- slaughter state in determining palatability. Locker and Hagyard (1963) demonstrated that early exposure of carcasses to cold induces muscle shortening, (``cold shortening''), and that such shortening can induce toughness. Electrical stimulation of muscles soon after slaughter hastens the onset of rigor mortis and provides the basis for processes to rapidly reduce muscle pH in lamb (Bendall, 1976; Carse, 1973; Chrystall, Devine, Ellery, & Wade, 1984) and beef (Chrystall & Devine, 1978; Davey, Gilbert, & Carse 1976), and thus avoid the tough- ening eects of cold shortening and thaw shortening. Most of the studies on electrical stimulation con- ducted in the past involved the application of high vol- tages (Polidori, Kauman, & Valfre, 1996; Smith, 1985). However, many authors (Eikelenboom, Smuld- ers, & Ruderus 1985; Kondos & Taylor, 1987; Nour, Gomide, Miller, Lemenager, & Judge 1994) have demonstrated a similar eect on pH fall with low vol- tage electrical stimulation techniques, although it was suggested that the resulting increase in tenderness was mainly due to the prevention of cold shortening. Many authors agree that low voltage is more practical (Fabiansson & Laser ReuterswaÈ rd, 1985; Hawrysh, Shand, Wolfe, & Price, 1987; Savell, Smith, Dutson, Carpenter, & Suter, 1977) for safety reasons a low vol- tage system is more attractive for application under commercial conditions. In general, the lower the voltage the less the danger to the operator and the less stringent the requirements imposed by government regulatory agencies for preventing accidents to employers. The present study has been designed to determine whether a low (28 V peak) voltage early post mortem electrical stimulation, through hastening rigor chan- ges, can signi®cantly reduce cold shortening in lamb carcasses. 0309-1740/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(99)00044-3 Meat Science 53 (1999) 179±182 www.elsevier.com/locate/meatsci * Corresponding author. Tel.:+39-0737-789-1; fax: +39-0737-789- 321. E-mail address: polidori@camserv.unicam.it. (P. Polidori)