DuPont gets presented with all kinds of interesting situations when we do technical service in a dairy plant. One recent event that comes to mind is worth mentioning, because it is something that we can all learn from. One plant was having trouble pumping cooled buttermilk onto a tank truck for use as an ingredient in making biscuits at a local bakery. The in-line screens were getting clogged up and eventually causing a severe loss of flow and making it impossible to empty the large 10,000-12,000 gallon silos of buttermilk into the tankers for delivery. Even if the buttermilk could be pumped onto the tanker from the producing dairy, once the tanker arrived at the bakery’s delivery dock, the bakery’s pump was used and the in-line screen at the bakery was also getting clogged up making unloading of the buttermilk tanker extremely difficult.
Since this dairy used our buttermilk stabilizer and another supplier’s culture, the culture supplier and I were called in to troubleshoot the problem for them. (Remember, when something goes wrong in a dairy, 99% of the time they think it is the fault of either the culture or the stabilizer). Upon arrival at the dairy, I was presented with the following in-line screen with whitish and yellow material on it. See photograph A above.
The culture supplier was already there and upon my arrival in the plant manager’s office he shouted out, “Look at this! Your stabilizer is clogging up these in-line screens.” Calmly I started to examine the in-line screen. As a food scientist, we are trained to use instruments to help us determine the body and texture of foods. I also rely on common sense and our senses of touch, feel, sight and smell to determine what might be the cause of the problem. I examined the whirl-pak bag and smelled the screen. Immediately, I smelled an odor of vinegar and/or diacetyl. I took a small amount of the material on the in-line screen and rubbed it between my index finger and thumb in a swirling motion. I was examining if the clumped material had a gritty feel to it, and if it dissolved or broke down when it was rubbed. It was not gritty, melted down smooth, and felt greasy, just like butter or fat clumps. If it was stabilizer, it would have a sandy or gritty feel to it, would not have melted in the palm of my hand or felt greasy, and would not have broken down or dissolved. We tasted the lumped material and guess what? It tasted just like butter! The plant manager’s comment was, “If it looks like a duck, walks like a duck, and quacks like a duck, then it must be a duck!” Mystery solved. It was butterfat! Since we knew what the material was, all we had to do now is find out where the butterfat clumps (or churned fat) were forming in the buttermilk.
My immediate comment was, “The only way I know how to get rid of churned fat is to homogenize it in”. The plant manager immediately said the buttermilk was homogenized. However, the production supervisor said it is only homogenized if it is processed on HTST #1. When it is homogenized on HTST #2 it is not homogenized. I said, “That is your problem right there. I don’t care where the buttermilk is processed from now on; I want it homogenized at 1000 p.s.i. on the HTST units.” I watched them batch up a 10,000 gallon batch of buttermilk. I was looking for places where the butterfat could be churned such as in the Liqwifier during batching. Sure enough, the 1% fat buttermilk usually has the skim milk used as the fluid mixture that is sent to the Liqwifier. However, the production supervisor said on some occasions that whole milk is added to the Liqwifier rather than skim milk and the stabilizer added to whole milk rather than skim milk. It was stated that, “How can the butterfat get churned when there is so little (1%) fat content in the finished buttermilk?”
I did the math and calculated that when 10,000 gallons of 1% buttermilk is made there is still 863# of fat in the product [10,000 gal. x 8.63#/gal = 86,300# of finished buttermilk made x (0.01 percent as a decimal at 1% fat) = 863# of fat that would have to pass through that in-line screen]. So apparently when whole milk was used to add the stabilizer, and when the buttermilk was run on HTST #2 without homogenization, churned fat clumps from either the Liqwifier or subsequent transfer pumps were remaining in the cultured buttermilk and clogging up the in-line screen after the buttermilk was cooled and transferred to the tanker for delivery to the bakery.
A lot of times deviations to procedures or improper processing methods are discovered in the dairy itself, which we discover when we go in and dig for information and talk to the personnel involved in making the product. The very next batch was made and homogenized on HTST #2 and the in-line screen looked like this (see photo B below) after the 10,000 gallons of buttermilk was cooled and pumped onto the tanker. In fact, after it was made certain that all buttermilk was homogenized, there was never a report of clogged in-line screens ever again!
Although this problem was not culture or stabilizer related, I do take great satisfaction in helping a dairy solve a problem. I share these experiences with you, our readers, so that it doesn’t happen in your facility! One thing experience has taught me is this: in the dairy industry many of the problems are the same, just the location changes!