Intramuscular fat and sensory properties of pork loin Susanna Cannata1, Terry Engle2, Steven Moeller3, Henry Zerby3, Phil Bass2, Keith Belk 2 Dipartimento di Scienze Veterinarie per la Sicurezza Alimentare, Università di Milano, Italy
1
Department of Animal Sciences. Colorado State University, Fort Collins, Colorado, USA
2
Department of Animal Sciences. Ohio State University, Columbus, Ohio, USA
3
Corresponding author: Susanna Cannata. Dipartimento di Scienze Veterinarie per la Sicurezza Alimentare. Facoltà di Medicina Veterinaria, Università degli Studi di Milano. Via Trentacoste 2, 20134 Milano, Italy - Tel. +39 02 50315753 - Fax: +39 02 5031574 - Email:
[email protected]
Abstract - Pork loins (n= 53) were selected from a commercial packing plant to determine the influence of subjective visual marbling score on sensory attributes and quality properties. The loins were obtained from commercial hybrid castrated male pigs originating from different herds fed similar commercial diets. Increasing subjective marbling score corresponded with decreased protein content, less percent drip loss, increased pH, and more desirable sensory tenderness and juiciness scores. Greater visual marbling scores resulted in more desirable sensory scores and may be used or included as one of the variables to evaluate fresh pork quality. Key words: Marbling, Pork quality, Sensory properties, Tenderness. Introduction - Degree of marbling or intramuscular fat/lipid content (IMF) is perhaps important from a sensory point of view. In fact it is generally accepted that an increased level of marbling has a positive influence on the sensory qualities of pig meat. Some authors reported significant correlations between the amount of intramuscular fat and eating quality of pork; in particular, lipid content often has been reported to influence the sensory traits of texture, tenderness, flavour and juiciness (Lonergan et al., 2007). It is generally accepted that a higher level of marbling or IMF has a positive influence on the sensory experience associated with eating pork (Wood et al., 2004). Pork flavor may decline with selection strategies that substantially reduce intramuscular fat content. Therefore, the aim of our study was to investigate the relationships between visual marbling and the principal sensory properties (tenderness, juiciness, and presence of off-flavors) as well as quality traits of pork. Material and methods - A total of 53 fresh, boneless pork loins from commercial hybrid castrated male pigs fed a diet based on corn-soy (16% CP, 0.90 Lysine) were selected in a commercial packing plant on the basis of their visual marbling. Loins were assigned to one of the three following marbling groups (MG): MG1, MG2 and MG3 (NPPC, 1999). After aging 7 days post-mortem (0 to 2����������������� °C��������������� ), loins were cut into 1.5 cm thick chops. Chops from the cranial end near the tenth-eleventh rib area were used to obtain moisture, protein, lipid and ash (AOAC, 2000), Minolta L*, a* and b* values (CR-310, Minolta colorimeter), and ultimate pH (HI98240, Hanna Instruments) using a glass-tipped pH probe (FC201D, Hanna Instruments). Drip loss was determined as a percentage of weight loss after 2 days storage at 4° C. Chops were cooked on George Foreman grills with temperature at 190°C until they reached an internal temperature of 70±0.5°C. The chops were weighed prior to and after cooking to determine cooking loss. Peak slice shear force was measured using a Texture Analyzer, equipped with a slice shear force attachment. The sensory panel (recruited from staff and graduate students at Colorado State University) was screened and trained using the guidelines and procedures of Meilgaard et al. (2007). Taste ������������������������������������������������������������������������������������������� panel sessions were designed such that no more than 6 or 8 samples were evaluated in Ital.J.Anim.Sci.
vol.
8 (Suppl. 2), 483-485, 2009
467-578_04_MEAT_II_BOZZA_ok.indd483 483
483
20-05-2009 10:53:02
Proc. 18th Nat. Congr. ASPA, Palermo, Italy
each session and a 8-point hedonic scale (table 1) was used to evaluate tenderness, juiciness and flavor intensity. Loin chops used for sensory testing were trimmed of external fat and epimysial connective tissue and cooked as previously described and cooking loss was recorded. The cooked chops were cut into 1.25 cm cubes using a plexiglass sample sizer (14 cm long x 12 cm wide x 4 cm deep with 3 mm slots spaced 1.25 cm apart on the 14 and 12 cm axis). The cubes were then served to the panelists on ceramic plates (Corino et al., 2008). Data were analyzed using the analysis of variance (ANOVA) with visual marbling as a treatment in a completely randomized design. All the analyses were obtained by using SPSS (SPSS, 2008).
Table 1. Scale
Eight-point hedonic scales used for sensory evaluation. Tenderness
Juiciness
Off-flavour intensity
8
Extremely tender
Extremely juicy
No off-flavor
7
Very tender
Very juicy
Trace off-flavor
6
Moderately tender
Moderately juicy
Slight off-flavor
5
Slightly tender
Slightly juicy
Small off-flavor
4
Slightly tough
Slightly dry
Modest off-flavor
3
Moderately tough
Moderately dry
Moderately off-flavor
2
Very tough
Very dry
Very off-flavor
1
Extremely tough
Extremely dry
Extremely off-flavor
Results and conclusions - In the present study, the influence of IMF on the quality of pork was assessed in pork loins ranging in IMF content from 1.5% to 4%. ������������������������������������� The effects of marbling on proximate composition and quality traits are shown in table 2. As expected, IMF content was higher at the increased marbling score (MG1 and MG2 vs. MG3; P < 0.001). Increasing marbling score did result in a lower protein content of MG3 than MG1 and MG2 in both raw and cooked samples (P= 0.012 and P= 0.037); this could likely be attributable to the increasing fat content on equal percentage of DM. Marbling score did not influence the visual colour scoring and the colour indexes L*, a* and b* as reported by Fernandez et al. (1999). A �������������������������������������������������������������������� significant effect of marbling group was found for pH. Loins from MG2 and MG3 were similar with respect to pH values, however they had a greater pH than MG1 loins (P
