Brussel Sprouts Turning Purple
Hello all,
I am new to the vegetable industry - so I do not have a lot of insight on this topic, but I need some help.
At my facility we run a number of vegetables and typically do not have any issues with our process, other than with Brussel Sprouts.
We receive them, wash them, blanch them, then add them into a jar or can with a brine, cook them in a pasteurizer and then package and ship.
As of this year, we have seen purple discoloration on the sprouts, after they have been cooked and are left to set for a week. We thought it might be from the crushed red pepper ingredients mixing into the brine and causing the color change. We use Sodium Metabisulfite to prevent the color change, however certain customers (Whole Foods) does not allow this ingredient to be added. We are currently testing Citric Acid to see if this will prevent the discoloration. We are not over-blanching or overcooking in our thermal process.
Does anyone know why they are changing color? Ways to prevent this from occurring?
Thank you for the help!
*This has nothing to do with food safety and I am not in the vegetable industry. Perhaps it might be related though...
In college (chemistry major) we did an experiment on pH and used cabbage juice to indicate acidity because it turned various shades of purple and pink throughout the pH scale. Brussel sprouts are in the cabbage family and your post reminded me of that experiment.
I hope you find a real answer but maybe it has something to do with acidity?
It may be a reaction of the chlorophyll with increased salinity (your brine solution) and/or pH changes. Therefore causing the sprouts to discolor from green to purple.
Thank you for the input!
I considered the pH and salinity to be the issue, however we are going off of a finished product specification that the company has always followed and everything falls into the spec.
This hasn't been an issue until the past couple of months. We have not had any changes in our specs or the ingredients - this is what's throwing me off.
No changes in the brussel sprout variety?
They did however change the blanching process (I just found this out.) Perhaps this could be the issue?
What has changed in the blanching process? Could you briefly share that please? Perhaps its a reaction combined with blanching along with the other attributes, like salinity and pH. Also you said you used crushed red pepper, perhaps thats also contributing to change in color. For example from where I come from, we pickle turnips, and we add beats in there, so it automatically turns the turnips purple from the beats. But if you have always been adding these peppers and you just found the problem happening, then the peppers are not the issue.
Currently we use a blancher that is 12 ft, we blanch the sprouts for 15 minutes at 200 degrees. Prior to this setup they were blanching in a kettle at the same time and temperature, and then placing them in a colder kettle for storage until they ran them down the line. I’m thinking that the cold water storage somehow was preventing the discoloration from occurring.
Is it possible that the growers have changed fields or chemical/fertilizer application? Some plants (Hydrangeas are the poster child for this) produce different compounds resulting in different pigments being present depending on soil conditions. In the case of Hydrangeas a low pH results in blue flowers. It's possible that similar changes might result in more production of the phytochemicals associated with the color change in the brussel sprouts.
That is a very good question, we use a broker to purchase our vegetables; we have asked him that information as well, hopefully we will hear back soon on this. It seems to take a while to get information from the grower, to him and then to us!
So they placed them in cold water after blanching, correct? When you place them in cold water after blanching you are basically "shocking" them, stopping the cooking process from proceeding, which may have contributed to the color of the sprouts. and now Since you are not doing that, they were not shocking and possibly further cooked, causing the color change along with brine and pH changes. I agree with previous post, you should defiantly check with your grower to try and see perhaps its the brussel sprouts themselves. If not then it is definitely somewhere in your blanching and post brining processes. You can carry out different tests by changing up the process to indicate where and what exactly is the issue coming from.
That is correct, I was unaware that this could be a potential issue. I'm going to start researching! Thank you!