E: Food Engineering & Physical Properties Effect of High Pressure and Salt on Pork Meat Quality and Microstructure Fr´ ed´ erique Duranton, H´ el` ene Simonin, Romuald Ch´ eret, Sandrine Guillou, and Marie de Lamballerie Abstract: The interaction of salt (0%, 1.5%, and 3% in the ﬁnal product) and a high-pressure treatment (500 MPa, 20 ◦ C, 6 min) was investigated using pork biceps femoris muscle. The Warner-Bratzler shear force and the water holding capacity (WHC) were assessed and linked to the microstructure evaluation by environmental scanning electronic microscopy (ESEM). Pressure-treated and cooked samples showed a high Warner-Bratzler shear force with a low WHC compared to control cooked samples. These negative effects could be linked to the general shrinkage of the structure as observed by ESEM. The addition of 1.5% salt was sufﬁcient to improve the technological properties of the high-pressure-treated samples and to counteract the negative effect of high pressure on texture and WHC. This phenomenon could be linked to the breakdown in structure observed by ESEM. This study states that it is possible to produce pressurized pork products of good eating quality by adding limited salt levels. Keywords: high pressure, meat, microstructure, salt, texture Introduction The high-pressure processing (HPP) has been widely studied for its pasteurizing effect on food products. Its potential to improve the shelf life of meat products is widely documented, and recent studies have focused on its technological impact. Indeed, pressure greatly inﬂuences the properties of myoﬁbrillar proteins, such as their solubility (Chapleau and de Lamballerie-Anton 2003; Lee and others 2007) and their capacity to bind water or to form gels (Yamamoto and others 1993). Such functional properties are related to meat texture and water retention in the product. Therefore, the use of high pressure as a technological tool has been considered, particularly for meat batters (Iwasaki and others 2006). In such products, HPP has been used successfully to reduce salt (Crehan and others 2000). Indeed, the cohesion of meat batters and emulsions is dependent on the amount of salt because the extraction of salt-soluble protein occurs in the binding of meat pieces. Pressure treatment (up to 400 MPa, 10 ◦ C, 2 min) of salted meat batters resulted in improved texture and water holding capacity (WHC) when cooked, compared to the control (Macfarlane and others 1984; Fern´ andez-Mart´ ın and others 2002). This improvement was explained by the pressure-induced solubilization of protein that could favor meat binding (Sikes and others 2009), as well as by the dissociation of the myoﬁbrils (Iwasaki and others 2006). The latter study showed that pressure- induced texturization enabled the manufacture of low-salt meat batters (1% w/w) with good quality characteristics after cooking. However, little is known about the effects of salt and high pres- sure on whole meat muscles, although they are commonly used MS 20120315 Submitted 2/28/2012, Accepted 5/15/2012. Authors Duranton, Simonin, and de Lamballerie are with GEPEA (UMR CNRS 6144), ONIRIS, Rue de la G´ eraudi` ere, BP 82225, 44322 Nantes Cedex 3, France. Authors Duranton and Ch´ eret are with CTCPA, Rue de la G´ eraudi` ere, BP 62241, 44322 Nantes Cedex, France. Author Guillou is with SECALIM (UMR INRA 1014), LUNAM Univ., ONIRIS, Atlanpole-La Chantrerie, Route de Gachet, BP 40706, 44307 Nantes Cedex, France. Direct inquiries to author de Lamballerie (E-mail: marie. de-lamballerie@oniris-nantes.fr). in chunk-type products such as cooked ham (Bertram and others 2006). The inﬂuence of pressure and salt on whole meat could be different compared to batters or patties. Indeed, connective tissue and myoﬁbrils are disrupted in batters, whereas they play a signiﬁcant role in whole muscle. In addition, salt-induced swelling of myoﬁbrils is restricted by the endomysial sheath (Wilding and others 1986). Recent research noted that HPP could be applied to value-added meat products, but that more research was needed to maximize the positive effects of HPP while minimizing the negative ones (Souza and others 2011). Indeed, the challenge is that HPP induces various changes in meat depending on the nature of the matrix (for example, type of meat and structure of the product), which prevents simple extrapolation to another matrix. The objective is to ﬁnd a compromise between the addition of salt and the application of HPP to obtain a low-salt product with acceptable quality characteristics. The aim of the present study was to investigate the effects of high pressure and salt on pork muscle that will be further cooked. Critical technological properties such as texture and WHC were assessed in order to evaluate the eating quality of the product. The integrity of the muscle after treatment was also evaluated using environmental scanning electron microscopy (ESEM). ESEM represents a new development in the ﬁeld of meat quality assess- ment (Damez and Clerjon 2008). This microscopic technique has been successfully used to investigate the microstructural changes in various meat types during heat treatments (Yarmand and Baumgartner 2000; Yarmand and Homayoumi 2010). Despite a lower contrast than scanning electronic microscopy, ESEM has the advantage of allowing the observation of fresh samples at normal atmospheric pressures. The absence of previous preparations of the sample minimizes the introduction of artifacts and offers the possibility of observing intact samples. Materials and Methods Preparation of samples Fresh biceps femoris muscles from different animals were col- lected from pork ham obtained at a local slaughterhouse (GAD, C  2012 Institute of Food Technologists R  E188 Journal of Food Science  Vol. 77, Nr. 8, 2012 doi: 10.1111/j.1750-3841.2012.02816.x Further reproduction without permission is prohibited