Mixing and Tumbling – Colour Loss and Binding
The system I developed over the years and used with great effect is to mix a batch of “stuffing meat” which I use in conjunction with whole muscles. Whether such a mix is made or comminuted muscle meat prepared for sausages, researchers have found that mixing time has an effect on the color and will increase the deterioration of the desired color if conducted in excess of 12 min” (Sun, 2009). Over the years I noticed a similar colour change if whole meat muscles have been over-tumbles, but if the meat is smoked, the colour change is immaterial.
The greatest benefit of the system relates to binding. The reason why I use “stuffing meat” is that this combines modern binding systems such as transglutaminase with old-school meat processing techniques, such as chunking, flaking and tearing. Bhaskar Reddy, et al. describes chunking and its benefits as “passing the meat through a coarse grinder plate leading to decrease in the particle size not greater than one and a half inch cubes. This technique increases the surface for the extraction of myosin and aids in better binding during mixing.” (Bhaskar Reddy, et al.; 2015) This describes the system I currently use to produce the stuffing meat. Bhaskar and his colleagues refer to flaking and say that “high-speed dicing or slicing machine is being used for flaking and reforming of restructured meat products. Fine flakes produce more acceptable appearance, increase tenderness and decrease shear force value”, referencing Mandal et al., 2011; Reddy et al., 2015. They add another category which they refer to as “sectioned and formed meats” which are “primarily composed of intact muscle or section of muscle that are bound together to form a single piece”, quoting Pearson and Gillet, 1996; Mandal et al., 2011; Sharma et al., 2013. This is the process then of taking the whole muscle meat and joining them together in the grid system. My method combines then chunking with sectioned and formed meats.
The “old school” method relies on the combined effects of salt, phosphate and mechanical action. Bhaskar Reddy, et al. (2015) references Boles and Shand, 1998 who found that “by using this technology, the product must be sold either precooked or frozen because the product binding is not very high in the raw state but high yields (25% above meat weight) are possible.
One of the benefits of the “old school” methods is the effect of meat particle size. “An increase in meat surface area and an increase in the availability of myofibrillar proteins for binding is the net consequence of comminution.” (Sun, 2009).
“In a study to evaluate mixing time on the binding effect of restructured meat, Booren, Mandigo, Olson, and Jones (1982) found that there was a significant linear increase in binding strengths up to 12 min of mixing at 28C.” (Sun, 2009)
The excellent review article of Sun (2009) makes reference to a study by Ghavimi,
Rogers, Althen, and Ammerman (1986) where they assessed vacuum, non-vacuum, and nitrogen back flush processing conditions at 1–38C during tumbling of restructured cured beef. Fascinatingly, they concluded that meat had higher cooked yields in a non-vacuum atmosphere. This, in the context of the application of Transglutaminase, is a very interesting observation.
I have long proposed a re-examination of the viability of vacuum tumbling, but I recognise the entrenched nature of this technology in modern meat processing plants and propose a new line set-up for investigation.
Injector -> vacuum tumbler -> 24 hours resting station -> add TG -> ribbon/ paddle mixer -> filling station -> smoking/ cooking -> de-gritting -> freezing – slicing -> packing.
This eliminates the re-routing of meat back to the tumblers which are expensive assets while it achieves the application of the TG, final pick-up of any brine that purged out of the meat during resting as well as the balancing brine added after injection. In order to facilitate a proper pick up of this “loose brine”, some processors choose to add between 1 and 2% pork protein at this stage which will mean that the brine added during this step consists of the pork protein and the TG blend in a small amount of brine.
Lets first look at why a tumbler works. The interaction of the meat, rubbing against the meat and the pressure created as the mass of meat falls to the bottom of the tumbler during the drum rotation causes pressure which then “activates” the protein by causing the highly swollen muscular protein cells to burst. Bhaskar Reddy, et al., (2015) quotes Feiner, 2006 who stated that it is the “kinetic energy released during falling of meat pieces at bottom of the tumbler which serves to disrupt cellular membranes, which in turn causes protein extraction. It is the baffles inside the tumbler which “move the injected pieces of meat up the wall of the tumbler and once the pieces of meat reach a certain height, gravity causes them to fall.” (Bhaskar Reddy, et al., 2015)
This is, in my opinion far more aggressively and successfully achieved through a paddle mixer or a ribbon mixer than only the falling of the meat inside the tumbler. Mixing in a paddle or ribbon mixer will, in my estimation, better develop the myosin protein to become “sticky.” Remember that the aim of this step is to “solubilize the protein, creating a layer of activated protein on the surface of meat which is responsible for slice coherency in the cooked product. The sarcolemma surrounding the tightly swollen muscle cells is, in my opinion, more likely to be destroyed by the impact of energy from paddles than only tumbling and myofibrillar proteins will be released and solubilized (which is the object of tumbling). There is considerable academic and anecdotal support for this. Dikeman and Devine state in their Encyclopedia of Meat science, second edition (2014), commenting on the fact that paddle mixers run at reduced revolutions per minute (rpm), that they “can be useful for applying mecahnical action to whole muscle pieces. . . to produce a surface protein exudate without damaging muscle integrity.” (Dikeman and Devine, 2014: 126, 127)
Meat must be mixed until they become tacky – almost furry. “Rust and Olson (1973) found that the extraction of myofibrillar proteins on the surface of meat has two functions. One is to act as a bonding agent holding the meat surfaces together and the other is to act as a sealer when thermally processed and therefore, aid in the retention of water in the muscle tissue.” “In addition, cellular disruption of the meat tissue occurs during tumbling which together with the curing additives allows the meat to improve the yield (Chow et al., 1986). Constraining connective tissue sheaths around muscle fibres are disrupted, allowing further myofibrillar swelling introduced by salt (Katsaras and Budras, 1993). (Bhaskar Reddy, et al., 2015)
It is, of course, possible to mix the TG mix into the stuffing meat by hand, but one loses all the benefits listed above. For the exact reason, I believe a more aggressive treatment of the whole muscle meat just prior to filling into the grids should yield far better reshaping and binding results. Too little mixing will result in meat being “loose” and a failure to bind together. Too much mixing, on the other hand, will result in a loss of tenderness and the product being “rubbery”. (Pearson and Gillett, 1999)
The reason why mixing is essentially done in a tumbler under vacuum is mainly that, removing the oxygen, prevents oxidation. This prevention of oxidation will, however, also be accomplished by maintaining a low temperature during mixing which is obviously also very good to control negative mirco-growth. (Pearson and Gillett, 1999)
Bhaskar Reddy and colleagues state that tumbling or massaging (physical action upon the meat, in whatever form) “improves the speed of curing by increasing salt absorption.” (Bhaskar Reddy, et al., 2015) It is this reason why I still prefer the two-step tumbling. The solubilization of the proteins by the fat and the phosphates are greatly enhanced if the meat is left to rest for 12 or 24 hours and re-tumbled/ mixed which of course will increase the protein bind.
Having made this statement, we get to a long-standing debate related to tumbling namely if one must tumble continually (uninterrupted) or if one must have intervals of rest periods. For every study that intermitted tumbling is superior, there seems to be a study that shows continues tumbling is superior. Why is the one preferred over the other? Exactly because brine needs time to diffuse into the muscle. (Krause et al., 1978) One needs the drum to stop turning so that the meat can be immersed in the brine in order to absorb into it. This is not achieved, as many believe, by the vacuum which presumably opens up the meat fibers and somehow pulls the brine into the meat. The reason why this is done intermittently (tumble, rest, tumble, rest) and not in a two-step process of tumbling, unloading, resting in the chiller, loading into the tumbler and tumbled again, is presumably to eliminate the need to load and unload the tumbler twice. In a high throughput factory, this should, in any event, be done with loading equipment and should not be a consideration. I also doubt if the total time of resting in a tumbling program will be sufficient for the brine to be absorbed if one takes absorption rates into meat into account.
Whichever way I look at it, a two tumbling system is preferred over injection, resting, tumble, adding TG 15 minutes before the end of the program and grid filling (only one tumbling step). There are simply too many advantages which are ignored which one will get in a system of injection, tumbling, resting, TG tumble, grid filling.
My only concern of using paddle mixers for the second step and not tumblers relates to the formation of foam. If foam is created, this may lead to protein denaturation and the binding strength will be compromised (Kerry et al., 2002) This will have to be evaluated. In my own experience, when using a blender to do the stuffing meat, this has never in 2 years of using the technique created foam. Whole muscles will have to be tested for foam formation which I know happens in a tumbler if only a partial vacuum is pulled. I suspect the paddle mixer will work very well.
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