Conventional freezing plus high pressure–low temperature treatment: Physical properties, microbial quality and storage stability of beef meat Pedro P. Ferna ´ndez a , Pedro D. Sanz a, * , Antonio D. Molina-Garcı ´a a , Laura Otero a , Be ´renge `re Guignon a , Sergio R. Vaudagna b,c,d a Instituto del Frı ´o (CSIC), C/Jose ´ Antonio Nova ´ is 10, 28040-Madrid, Spain b Instituto Tecnologı ´a de Alimentos, Centro de Investigacio ´ n de Agroindustria, Instituto Nacional de Tecnologı ´a Agropecuaria (INTA), CC 77, B1708WAB, Moro ´ n, Argentina c Consejo Nacional de Investigaciones Cientı ´ficas y Te ´cnicas (CONICET), Buenos Aires, Argentina d Facultad de Agronomı ´a y Ciencias Agroalimentarias. Universidad de Moro ´ n, Moro ´ n, Argentina Received 12 June 2006; received in revised form 16 May 2007; accepted 21 May 2007 Abstract Meat high-hydrostatic pressure treatment causes severe decolouration, preventing its commercialisation due to consumer rejection. Novel procedures involving product freezing plus low-temperature pressure processing are here investigated. Room temperature (20 °C) pressurisation (650 MPa/10 min) and air blast freezing (30 °C) are compared to air blast freezing plus high pressure at subzero temperature (35 °C) in terms of drip loss, expressible moisture, shear force, colour, microbial quality and storage stability of fresh and salt-added beef samples (Longissimus dorsi muscle). The latter treatment induced solid water transitions among ice phases. Fresh beef high pressure treatment (650 MPa/20 °C/10 min) increased significantly expressible moisture while it decreased in pressurised (650 MPa/35 °C/10 min) frozen beef. Salt addition reduced high pressure-induced water loss. Treatments studied did not change fresh or salt-added samples shear force. Frozen beef pressurised at low temperature showed L, a and b values after thawing close to fresh sam- ples. However, these samples in frozen state, presented chromatic parameters similar to unfrozen beef pressurised at room temperature. Apparently, freezing protects meat against pressure colour deterioration, fresh colour being recovered after thawing. High pressure pro- cessing (20 °C or 35 °C) was very effective reducing aerobic total (2-log 10 cycles) and lactic acid bacteria counts (2.4-log 10 cycles), in fresh and salt-added samples. Frozen + pressurised beef stored at 18 °C during 45 days recovered its original colour after thawing, sim- ilarly to just-treated samples while their counts remain below detection limits during storage. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: High pressure processing; Freezing; Beef meat; Colour; Microbial inactivation 1. Introduction The application of high pressure processing (HPP) to meat and meat products above 0 °C has been investigated in numerous studies since 1970s (carefully reviewed by Led- ward, 1998; Montero & Go ´mez Guillen, 2005). High pres- sure treatment is emerging as a high interest technology, due to its capacity to preserve the essential functional and nutritional characteristics of food products. Even though the initial investment is still high, pressure treat- ments consume less energy than thermal processing, a fac- tor contributing to its commercially competitiveness (Garriga, Gre ´bol, Aymerich, Monfort, & Hugas, 2004). High pressure technology could be a powerful tool for increasing the safety and shelf life of fresh and salt-added 0309-1740/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2007.05.014 * Corresponding author. Tel.: +34 91544507; fax: +34 915493627. E-mail address: psanz@if.csic.es (P.D. Sanz). www.elsevier.com/locate/meatsci Available online at www.sciencedirect.com Meat Science 77 (2007) 616–625 MEAT SCIENCE