ISO 9001 Quality Manuals

I was working with a starch stabilised ambient yogurt with a few months shelf life. It was a great product it looked good, tasted great and was easy to manufacture. We had no problems with the product quality for many years then all of a sudden the Laboratory Manager called me “You have to come and look at the shelf life samples”. I rushed down to the Laboratory and there they were all completely separated. We gave them a stir but within minutes they were separated again. “Check the previous week’s production” I said trying to think what the problem could be. “Those idiots in production haven’t put the right stabiliser in” was my initial thought!

The previous weeks were the same. In fact as we checked back we found that separation started after a few weeks. We checked the recipe sheets for each batch and reconciled orders and usage of stabilisers against production volumes. Everything was in order. We checked processing temperatures and times. Everything was in order. We checked base holding times and temperatures. Everything was in order. In fact we checked everything that could possibly go wrong in the factory and could not find anything out of the ordinary.

We consulted our suppliers. We had used several different ingredients batches but quarantined everything and ordered new batches of ingredients.

Still the problem persisted.

Everything looked great on day 1 but a month later they were separated. Our stabiliser supplier was a highly reputable company with an exemplary record, their retained samples of stabiliser performed perfectly under test.

We analysed the separated products and found amylase activity. The only logical conclusion after our extensive investigation and actions but where had it come from? Amylase is heat sensitive, how could it have got into the product after our process? The short answer is it couldn’t.

We researched far and wide into amylase activity and stability. “Surely as an enzyme and protein based any amylase would be completely denatured by our process” I said.

We analysed all of our ingredients for amylase activity and found it in several. Our process involved high temperatures and holding times and reprocessing of the yogurt base so we subjected all of our ingredients to the same conditions in the Laboratory. The result was a complete surprise. “It’s in the Sugar” the Laboratory Manager exclaimed.

We used Cane Sugar and now believe that amylase may be used in third world countries to help extract the sugar or it is present in diseased plants. The refinery assumed that any enzyme activity would be destroyed by the refining process. It was not. It was a freak of nature. Somehow, someway the enzyme had managed to develop heat resistance to survive our process.

We were able to source another supply of sugar which was clear of amylase activity and after a month I was able to sleep again!

Background Information

Amylase is an important metabolic enzyme. Its function is to catalyze the hydrolysis of starch into glucose. Normally at high temperatures, Amylase becomes denatured. Denatured amylase no longer catalyzes the hydrolysis of starch into glucose. Amylase is present in human saliva, where it begins the chemical process of digestion. Foods that contain much starch but little sugar, such as rice and potato, taste slightly sweet as they are chewed because amylase turns some of their starch into sugar in the mouth. Plants and some bacteria also produce amylase. Specific amylase proteins are designated by different Greek letters. All amylases are glycoside hydrolases and act on glycosidic bonds.