Teachers' notes - Miss Margaret Dick (1918-2008), food microbiologist

New responsibilities: from preventing failed vats to inspecting factories

When did you become the Chief Bacteriologist, in charge of quality control?

I was Senior Microbiologist for some years before I was made Chief Bacteriologist. The reason for that was that we had a male microbiologist at one of our country factories – Derek Shew, at Allansford factory – and he had been there longer than I had. He was the centre for the microbiology of most of the cheese factories we had.

He worked in the laboratory initially, doing some interesting work on the fact that when you make cheese you can get failed vats. That means that the cheese starters don't produce acid. The starters are cultures of organisms that are added to the vat to produce acid, which causes the moisture to come out of the cheese so that you get curds and whey. Then you can work on the curd and produce the bulk cheese as you know it today.

He could not understand the reason for these failed vats, but he found in a published article by Whitehead, in New Zealand, that he had discovered a particle which he believed attacked cheese starters. So Derek Shew went over to see Whitehead and worked with him, trying to sort out the problems with these bacteriophages, as they were called, to see how we could prevent them from causing the cheese vats to fail.

The bacteriophage is rather interesting. It is a virus-like particle which enters the cell, and instead of the cell multiplying itself, the phage multiplies within it to produce anything up to six to sixteen phage particles. That causes the cell to burst, releasing a whole lot of all these phage particles, which then can attack new starter cells. It is a big problem, and I think it is still with us. Derek Shew worked very hard on preventing failed vats, and eventually I got involved with it too when he had to leave because of his wife's health.

Then we got involved with all the cheese factories. Each cheese factory had its own manager, and of course it wasn't up to me to decide, 'I'm going down there to investigate their factories,' but I was soon told I had to do it. Mr Osborne walked into my office and said, 'Do you go round the cheese factories? I think you should' – just as he said later on, 'Do you go through all the new plant with the engineers while it is on the drawing board?' When I answered, 'No,' he said, 'Well, I think you should.' He was directing me in the factory area, to make sure that I went round everywhere.

I have a vision of you as a young woman suddenly thrust into this very complex and diverse experience, not just at the research bench but in the whole business of devising methodology and procedures, and formulating plans for better work and cleaner, more hygienic systems. I gather that once you began to go round the cheese factories you and your team were assessing their quality control.

Yes, we used to do technical audits. They always liked to know when I was coming. Particularly, at one stage we bought a fish factory at Eden and then we had to go and sort it all out. The engineers went in and devised ways of cutting tuna efficiently and easily so that the people didn't have back-breaking jobs to do. And we went in regularly to audit their cleanliness and sanitation. I remember one day driving down the hill towards the factory, with the wind blowing just in the right direction. You could smell the hypochlorite – they were getting ready for me!

Keeping ahead: testing for penicillin and enterotoxins

As the Kraft company grew to pre-eminence in Australia, developing whole sets of new products, your microbiological work came to include research on penicillin and staphylococcal enterotoxins, for example. Was work on such a series of problems distinctive to that company, or was some of it going on in other places?

Well, we were always first. We never knew really what other companies were doing. We seemed to be always ahead of everybody, but that was our aim: we wanted to keep ahead of our opposition. Quality was always the first thing.

When penicillin became available, the vets started to use it for the treatment of mastitis in cows. This became a vital thing for us, because as part of our quality the suppliers were supposed to keep the milk back for two to three days before it was allowed to go into the factory. Kraft, at all their country locations, used to employ field officers who would go out to the dairies and watch the cleaning, the sanitation, and talk to the farmers about any problems they had. In other words, they were watching the quality of the milk coming in. (In my earliest days there, it came in milk cans; then it was stored in refrigerated milk tanks; and then refrigerated tankers used to bring it to the factory. So there were big changes.) But this penicillin was a problem, because it could stop the starters from working in the vats. So we started to test for it.

Originally, the testing was done with a methylene blue test. The standard assessment before milk would be paid for was that the quality had to be up to a certain standard of methylene blue. But when you had penicillin in the milk, the methylene blue never went white. So few organisms would grow in the milk that it stayed blue for days! We decided we needed a better way of testing for penicillin. A test was devised by Jill Naylor, who worked in my lab, and that was put into practice. We used to assess all the suppliers' milk to all country factories every so often for penicillin, and report back to the factories.

And what about the staphylococcal enterotoxin? Just what is enterotoxin?

Enterotoxin is a name devised to explain a material that is produced by the growth of staphylococci which upsets the stomach. It is not caused – this is important – by the organism growing in your stomach, as it does with salmonella, but by the toxin produced in the food by the staphylococci. When you eat that food, you eat the enterotoxin. That is why it is called 'entero' rather than an endotoxin.