Effect of eight weeks chilled or frozen storage on consumer-defined sensory quality traits of lamb Cassius E. O. Coombs1,2,3, Benjamin W. B. Holman1, Remy J. van de Ven4, Michael A. Friend2,3 and David L. Hopkins1,2 1
Centre for Red Meat and Sheep Development, NSW Department of Primary Industries, Cowra NSW 2794, Australia 2
Graham Centre for Agricultural Innovation, Charles Sturt University, Wagga Wagga NSW 2650, Australia
3
4
School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga NSW 2650 Australia
NSW Department of Primary Industries, Orange Agricultural Institute, Forest Road, Orange NSW 2800, Australia Presenting author: Cassius Coombs
[email protected]
Summary The effects of eight weeks chilled and frozen storage on lamb m. longissimus lumborum (LL) were evaluated in this study. A total of 24 randomly selected LL were kept under chilled or frozen storage – the latter involving two different frozen storage temperatures of -12°C and -18°C. At the completion of the treatment phase, all LL were sub-sampled, cooked and tested by 30 untrained consumer panellists for tenderness, juiciness, flavour and overall liking quality traits. This study found that all quality traits were lower when LL were kept under frozen storage compared to chilled storage (P < 0.01). No difference between frozen storage temperatures was found (P > 0.05). These results demonstrate the consumer preference for chilled storage, in terms of LL eating quality when the storage duration is eight weeks. Introduction Sensory quality, as measured by consumer panels of varied levels of training, is fundamental to determining the effects of chilled and frozen storage on meat. Tenderness, juiciness, flavour and overall liking have been used in several studies to determine quality (Thompson et al., 2005). Past studies have reported frozen storage duration to have no detrimental effect on these quality traits of lamb, even following 2 years frozen storage (Winger, 1984). Chilled stored lamb, however, has been found to remain of acceptable quality for up to 12 weeks (Sumner & Jenson, 2011). Evident in these studies is the absence of a chilled and frozen storage comparison, and an evaluation of frozen storage temperature. This study therefore aimed to investigate this paucity using an untrained consumer sensory panel. Materials and Methods At 24 h post-mortem, 24 lamb LL muscles were randomly sampled from the boning room of a commercial Australian abattoir. All LL were vacuum-packaged and allocated to either chilled (n = 12; 8 weeks at 1-4°C) or frozen storage (8 weeks; n = 6 at -12°C and n = 6 at -18°C). At the conclusion of the frozen storage period, samples were allowed to thaw overnight under refrigeration.
Each LL was sliced into 5 slices, and then each slice halved to form 10 bite-size pieces per sample for scoring, with slices and half-slices for each sample tracked. These were grilled to an internal temperature of 71°C and presented to a panel of 30 untrained consumer panellists across two sessions, so that each LL was evaluated by 10 panellists. Panellists were provided a blank sample prior to experimental samples. Samples were rated out of 100 using sliding scales for tenderness, juiciness, flavour and overall liking (Thompson et al., 2005). Data were statistically analysed using a linear mixed model (R Core Team, 2015). Fixed effects were treatment (chilled storage and frozen storage at -12°C and -18°C) and sensory panel session. Uncorrelated random effects were individual sample, slice within sample, tester and freezer, as well as random error. The level of significance of this study was set at P < 0.05. Results Frozen storage resulted in lower rankings for all quality traits (P < 0.01) when compared with chilled storage, especially evident for tenderness and juiciness (Table 1). It was also evident that frozen storage temperature did not influence the evaluated sensory quality traits (P > 0.05).
Table 1. Mean consumer rankings (%) and standard error for lamb m. longissimus lumborum sensory quality traits kept for eight weeks under chilled or frozen storage
Treatment Chilled
Tenderness 66.6 (4.2)***
Juiciness 72.4 (4.8)***
Flavour 66.3 (2.6)**
Overall Liking 67.4 (3.4)**
Frozen (-12°C)
37 (5.7)
61.1 (5.2)
56.7 (3.3)
48.7 (4.6)
Frozen (-18°C)
48.4 (5.7)
64.3 (5.2)
59.5 (3.3)
54.6 (4.6)
** and *** denote significance as P < 0.01 and P < 0.001, respectively, for Chilled vs. Frozen comparison. Discussion
References
This study demonstrated that untrained consumer panellists can differentiate between chilled and frozen storage of lamb LL in terms of sensory quality traits. Past research has complemented these results, reporting diminished sensory quality with frozen storage, albeit using trained sensory panellists (Lagerstedt et al., 2008; Vieira et al., 2009). However, the present findings differ from other studies, for example Muela et al. (2012) reported that frozen storage for up to six months did not influence any sensory parameters in lamb. Another study only reported decreased juiciness in lamb after one month frozen storage (Bueno et al., 2013). The divergence of these and the present findings is thought to be based upon the differences in storage duration of chilled product to which frozen product was compared. Essentially, the chilled storage duration was much less in previous studies than that applied in the present study, and Vieira et al. (2009) noted that increasing the chilled storage duration from 3 days to 10 days significantly improved both tenderness and overall acceptability regardless of frozen storage duration, which is in agreement with other studies reporting peak lamb tenderness to occur between one and two weeks chilled storage (Dransfield, 1994).
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From this study, it can be concluded that regardless of temperature, lamb LL stored chilled for 8 weeks was of superior sensory quality compared to lamb LL stored frozen for 8 weeks. For future studies, the use of chilled storage prior to frozen storage may prove beneficial to lamb meat quality. Acknowledgements The authors thank the Australian Meat Processor Corporation (AMPC) for their financial assistance as well as the NSW Department of Primary Industries (NSW DPI) staff for their expertise and technical support.
