Case Study - Help with Fermented Dressings

Recently we received a couple of customer complaints about one type of the dressings we made was fermented which were still in date.

Some of the dressing were bubbling, flowed from the tub after transportation (refrigerated vehicle) and smelled funny.

I did a in-house temperature/time test on this product, I left one tub in ambient temperature and it went off after one week, the other one left in coolroom is still good after 3 weeks.

The original ph reading is 4 and drops to 3.2 when it's off.

The ingredients list of the dressing are:

Paprika
Capsicum (Canned)
Canola oil
Almond meal
Garlic (raw & roasted)
Vinegar
Chilli flakes
Sugar
Tomato paste (Canned)
Salt
Black pepper
Starch
Gum
Water

I try to isolate the 'trouble maker' from the beginning and would like to discuss this issue with the people here. Any input is more than welcomed.

Thank you in advance.

Hi,

from the effects of the fermentation and the pH range of your dressing, I would suspect yeast fermentation as the culprit in this case (Zygosaccharomyces). Yeasts occur naturally in the environment and can contaminate products through the air. A 'funny' smell could come from fermentation of sugar to alcohol. Yeasts are capable of growing in acidic environments and in refrigeration temperatures. Lactobacilli can also contribute to your spoilage problem. The drop in pH is a hint for this.

Strategies against yeast contamination include: rigorous hygiene (frequent, thorough cleaning), pasteurization of the final product in its closed container or sterilizing containers and filling with pasteurized product (not as effective as airborne yeasts can re-contaminate).

Final clarity on the source of contamination will only be obtainable by identifying the spoilage agent (microbiolgical analysis) and subsequent search for the source of the contaminant in the environment (surface swabs, raw material analysis). This will also help to determine action that is needed to eliminate the source of contamination.

For more information see here (Spoilage of Salad Dressings) and here (Zygosaccharomyces).

My initial advice: cleaning, cleaning, cleaning!

Dear MKRMS,

Thks for input. Unfortunately yr 1st link was inaccessible to me (source is somewhat of a lottery of course. ) Perhaps a snapshot ??

Rgds / Charles.C

Hi Charles.C,

thanks for mentioning the accessibility problem. Here are PDFs of the three pages I think are most relevant (from what is accessible). Source is: Downes, F.P., Ito, K.: Compendium of Methods for the Microbiological Examination of Foods. Washington DC.: American Public Health Association, 2001, pp 542-544. Page 543 is prob. most relevant.

542 Downes, Ito-Compendium of Methods for the Microbiological Examination of Foods.pdf   220.79KB   37 downloads
543 Downes, Ito-Compendium of Methods for the Microbiological Examination of Foods.pdf   187.51KB   22 downloads
544 Downes, Ito-Compendium of Methods for the Microbiological Examination of Foods.pdf   184.99KB   23 downloads

Hello. I have a fairly strong background in Salad Dressing/Sauce Manufacturing and have had a similar problem in the past. Your problem sounds more like a Lactic Acid (Lactobacillus) problem than yeast since the Lactic Acid bacteria is also a gas producing organism. The reason being that since your pH dropped from a 4.0 down to a 3.2, this is probably due to the creation of Lactic Acid in your product due to the fermentation that is occurring. The source of the Lactic Acid bacteria is more than likely the fresh/raw garlic. If you need to continue to use the raw garlic, the easiest way to fix this problem is to pre-soak the raw garlic at least 12 hours ahead of production with some of the formula vinegar (and some formula water if there is not enough vinegar to properly cover all of the garlic). But do not dilute the vinegar too much or you will raise the pH of the pre soak too high and it will not be effective in taking care of the Lactic Acid bacteria. If you have access to a microbiological lab, test the garlic for Lactobacillus before and after the vinegar pre soak. It will confirm that the raw garlic is the problem and also confirm that the pre soak is effective. Also, please keep the pre soak under refrigeration during the pre soak period. Thank you and good luck.

Thanks for all the above replies.

I sent some almond meal for testing last week which is the biggest concern of mine. The results came back with the yeast level 800cfu/g and lacto 300cfu/g. These number are not bad for dry blends, but considering the low pH level of the final products, the bugs could grow promptly as the growth of the other competitor had been inhited, especially during the transpotation by the external company where we can't control the temperature.