Since itâ€™s Friday and itâ€™s been a long (but fun!) couple weeks of some work and a lot of play, Iâ€™m going to keep things simple for you all today. For those of us in the Northern Hemisphere, weâ€™ve officially kicked off the grilling season! What better to celebrate the unofficial start of summer by talking about one of the most popular ingredients in back yard BBQs: beef!
Anyone familiar at all with the concept of meat is that over time, it spoils. You leave a hunk of beef out for too long prior to eating it, youâ€™re probably in for an â€śinterestingâ€ť night. There is also the problem of the meat going bad prior to someone purchasing it, in which case the store has no choice but to throw the meat away and suffer the economic losses.
Instead of using chemical presevatives to extend the shelf life of meats, as well as a greater movement to move toward a more â€śorganicâ€ť approach, consumers have been pushing the meat industry to move toward a more â€śnaturalâ€ť options when it comes to preservatives, and less of the 14 letterchemicals that no one recognizes.
One way that has been shown to preserve meat and extend the shelf life for a longer period of time more naturally is to use marinades. Not only do marinades extend the shelf life of meat, but it also improves the tenderness, palatability, and flavor. Wine is often a main ingredient in many marinades, thus why this particular blog is interested in this topic! In addition to marinades, some natural essential oils coming from plants have been shown to have excellent antimicrobial characteristics, though it should be noted that one of the most effective essential oils, coming from the plan genus Thymus, possess very negative flavor and aroma characteristics even when used at low concentrations. Itâ€™s possible that perhaps by combining the wine marinade with the essential oils that youâ€™ll get the awesome microbial benefit of both the wine and the essential oils without the negative flavor characteristics that usually comes with the use of essential oils.
The most recognized spoilage organisms in meat is probably Salmonella. There are many different strains of Salmonella, some more adapted to harsh environments than others. Specifically, some strains of Salmonella have undergone what is known as â€śacid adaptationâ€ť and that when exposed to higher acid environments, they still survive and thrive, whereas a strain that is not acid adapted will die. The trick is trying to find a mechanism for protecting the meat against multiple types of Salmonella or other spoilage microbes without injecting tons of crazy chemicals that no one really wants in their bodies.
The goal of the short study presented today was to examine the effects of wine and wine plus essential oil marinades on the survival of three strains of Salmonella and to determine which (if any) could be used as more natural alternatives to chemical preservation in beef.
The three Salmonella strains used in this experiment were: Salmonella Typhimurium DSM 552 (LT2 genotype hisG46; laboratory made), Salmonella Typhimurium DT 193 (isolated from humans, drug resistant), and Salmonella Typhimurium 4/74 (isolated from calvesâ€”the animal, not your lower leg).
Each Salmonella strain was treated to be acid-adapted or not acid-adapted. An equal number of each strain was then combined to make a multi-strain cocktail to use in the spoilage experiments with beef.
Beef was purchased from a local market and cut into 25g fillets of 1cm thickness. Beef samples were then inoculated with 100uL of the multi-strain Salmonella cocktail.
After inoculating with the multi-strain Salmonella cocktail, the following treatments were performed:
â€˘ Beef left out for 1 hour at 4 oC then submerged into red wine.
â€˘ Beef left out for 12 hours at 4 oC then submerged into red wine supplemented with 0.5% thyme essential oil.
â€˘ Untreated control beef: kept at 4 oC for 12 hours.
After these treatments, beef slices were then individually packaged and stored at 5 oC. Half of the samples were stored in air-tight plastic pouches, while the other half of the samples were stored in petri dishes exposed to the open air.
Microbial samples were analyzed before marination, Â˝ a day after marination, then on days 2, 4, 7, 11, 14, and 19 days after marination. Numbers/counts of Salmonella were measured on the beef samples, as well as Pseudomonas spp., lactic acid bacteria, and Enterobacteriaceae.
Sensory analysis of the beef samples were performed by a panel of 11 from the research laboratory. Samples were analyzed for color and taste after cooking the beef at 220 oC. Color and taste characteristics were scored on a 3-pt hedonic scale: 1 = acceptable; 2 = marginal; and 3 = unacceptable. Score less than 1.5 were considered fresh, scores equal to 1.5 were considered semi-fresh, and scores greater than 2 indicated that the meat was spoiled and at the end of its shelf life.
â€˘ The pH of fresh beef (no treatment) was 5.50.
o Marination in wine significantly decreased the pH of beef by between 0.92 and 1.27 units.
o Marination in wine plus thyme essential oils significantly decreased the pH of beef by between 0.89 and 1.30 units
o The pH of marinated beef remained constant throughout storage time whereas the pH of untreated beef significantly increased over storage time.
â€˘ Marinating in both wine and wine plus thyme essential oils significantly decreased the numbers of Salmonella compared with untreated control samples.
o Acid-adapted Salmonella were more sensitive to the wine plus thyme essential oil treatment than the wine treatment alone.
â€˘ By day 7, Salmonella counts dropped below the limit of detection in samples treated with wine plus thyme essential oils.
o Salmonella counts dropped more gradually for samples treated in wine only.
â€˘ Surviving Salmonella were not affected by acid-adaptation or storage conditions (i.e. air-free or exposed to air).
â€˘ Both wine only and wine plus thyme essential oils were effective against other the other bacterial organisms: Pseudomonas spp., lactic acid bacteria, B. thermosphacta, and Enterobacteriaceae.
o Wine plus thyme essential oils decreased the populations of these bacteria more than wine alone.
â€˘ All three individual Salmonella strains survived the marination in both wine and wine plus thyme essential oils in similar proportions, though all were significantly decreased compared with the no treatment control (more so with the wine plus thyme essential oil treatment).
â€˘ Sensory analysis indicated that the wine alone treatment provided the longest shelf life, followed by the wine with essential oils treatments, and then in last place the untreated control treatment (the shortest shelf life).
o Those samples stored without exposure to air had a longer shelf life than those samples expose directly to the air.
The results of this study are clear in that marinating beef in wine or wine plus thyme essential oils significantly reduces the number of Salmonella colonies, thus extending the shelf life of the meat. In addition to Salmonella, other potentially harmful organisms were significantly reduced (or eliminated), including Pseudomonas spp., lactic acid bacteria, B. thermosphacta, and Enterobacteriaceae. While both wine and wine plus thyme essential oils treatments were effective in reducing spoilage bacterial levels, the wine plus thyme essential oils treatment was the best performer. Adding thyme essential oils appears to further increase the antimicrobial effectiveness of the solution, which was already relatively high due to the presence of the wine.
The study also showed that having an adaptation to acidic environments did not help the Salmonella survive in the wine and the wine plus thyme essential oilsmarinades. The authors concluded that this may be due to the fact that there is a lot more complexity in wine than other acidic environments, and that there are a lot of barriers the Salmonella would have to cross in order to survive and they were simply too overwhelmed.
According to these results, using wine, and in particular wine plus essential oil marinades may be an effective preservation method for beef, which is a much more natural alternative than synthesized chemical preservatives. Itâ€™d be interesting to see how effective these marinades are in other meats or foods, to see if this technique can be used with other meats or if itâ€™s just an effective solution for microbial defense in beef.
What do you all think of this study? Please feel free to comment!
Source: Nisiotou, A., Chorianopoulos, N.G., Gounadaki, A., Panagou, E.Z., and Nychas, G-J.E. 2013. Effect of wine-based marinades on the behavior of Salmonella Typhimurium and background flora in beef fillets. International Journal of Food Microbiology 164: 119-127.