Having worked in a production environment previously, I know how equipment breaks down from time to time. With sour cream incubation taking such a long time, the question came up, “How long can you let it sit there before it has to be packaged”?
Recent FDA regulations say that sour cream needs to be packaged and down to a core temperature of 45F or less after 72 hours. That gives you basically 3 days from the time the sour cream is ready to be broken and packaged (if you break it at all) until it needs to reach a core temperature of 45F or less. Core temperature depends upon package size, and how long the product is in the cooler before it is shipped out. It also depends upon how well the cold air circulates in your refrigerated cooler and the temperature of the cooler itself.
In this example let’s assume the biggest retail package you are filling is a 16 oz. package size. You know from experience that when your sour cream is packaged at an incubation temperature of 76F it takes approximately 36 hours to cool the core of the pallet of 16 oz. retail cups to 45F or less. And this probably depends upon cases placed on the pallet (pallet configuration) and where those pallets are stored in your refrigerated warehouse. One trick to cool down the sour cream faster would be to place the pallets in the cooler with fans blowing the cold air on the pallet or to place the pallets right in front of the air circulation fans in the cooler. In this example, you would have 36 hours to package the sour cream and get it into the cooler to cool it down within the 72 hour requirement. That means if you have filler or casing issues, you can let your sour cream sit in the incubation tank at set temperature for 1 ½ days.
You may ask yourself what does this do to the product? The answer is that the sour cream culture continues to grow until the pH gets down to about a pH of 4.30. Usually some wheying off will occur on the top of the coagulum or perhaps between the outside wall of the setting tank and the sour cream coagulum itself. However, this whey can be mixed into the sour cream when it is “broken” or stirred with the vat agitator right before packaging begins. Stirring sour cream for 3-5 minutes right before it is packaged is usually enough time to remix in any whey separation and get the product homogeneous for packaging.
Taste-wise, sour cream is already sour and pH 4.30 sour cream will not taste that much different than pH 4.55 sour cream. Granted it might have a higher acid taste or bite to it, but isn’t sour cream supposed to be “sour”? In some cases, more of an acid bite might be a desirable trait. In today’s production environment where time is money, a lot of times we get anxious waiting on a tank of sour cream to come down to the break pH. Frequently, the flavor has not sufficiently developed yet. Letting sour cream sit there longer before packaging will assure you have developed the diacetyl flavor to the highest degree. The flavor producing strains in sour cream, namely the Streptococcus diacetylactis and the Leuconostoc strains will have had the chance to have complete fermentation of the inherent citrate in milk and convert it to the flavor compound, diacetyl and with subsequent CO2 production. This happens in the last hour or so of a typical sour cream fermentation when the lactic acid bacteria (Streptococcus lactis) have lowered the pH to 4.6 or lower. Letting the pH drop to 4.30 assures complete flavor development.
One production procedure that worked quite well at one dairy was to have a cleanup man come in on a Saturday and heat up the pasteurized cooled sour cream mixture run into the incubation tank on a Friday to the set temperature of 74F. He would put the culture in, agitate the mixture for half of an hour, and then let the sour cream sit quiescently for 14-18 hours until the pH came down to the break pH of 4.5 on Sunday morning. Nothing would happen for 24 hours and then the sour cream was packaged first thing Monday morning when the filler crew would start at 6 a.m. In this case, it was perfect “production timing” to have sour cream ready to be packaged first thing Monday morning by setting it 36 hours previously. Although this dairy had “given up” 24 hours by not packaging on a Sunday, they always felt they would have the retail cups down to 45F or less as they still had 48 hours to get it there, and knew it would get there in 36 hours. Timing is everything!