33 Food & Beverage Analysis


contact with LN2. For heavy-metal-free grinding a zirconium oxide grinding jar should be used. Further suitable materials are stainless steel or single use vials (1.5 or 2 ml). A few


pieces of liquorice, one praline with liquid fi lling or some beans of green coffee are typical samples for the CryoMill.


Large Sample Volumes with Small Initial Sample Size in the Ultra Centrifugal Mill ZM 200


The Ultra Centrifugal Mill ZM 200 accepts large sample volumes up to 4 l with a feed size < 10 mm, such as 100 g cereals, 150 g onions or 100 g dried apple pieces. The


sample is directly immersed into a container fi lled with LN2 before being continuously but slowly fed to the hopper of the mill with a steel spoon. When using dry ice as grinding aid, this needs to be mixed with the sample (1 part sample, 2 parts dry ice) and the entire mixture is then pulverised in the mill. Using a cassette in combination with a cyclone is recommended for cryogenic grinding to ensure that the evaporating cooling agent is completely discharged during the grinding process.


Figure 3: Liquorice before and after grinding in the CryoMill


Medium Sample Volumes with Medium Initial Sample Size in the Knife Mill GM 300


Medium sample volumes of up to 2 l with a feed size not bigger than 40 mm, such as 500 g wine gum, 250 g grapes, 400 g pure bacon or 800 g raisin, can be homogenised


perfectly in the GM 300 by using dry ice snow as grinding aid. The use of LN2 is not recommended as the mill is not designed for temperatures as low as -196°C. The sample is mixed with dry ice in a ratio of 1:2; after a few minutes, it is thoroughly cooled, and the grinding process starts. The dry ice keeps the sample cool all the time. Care should be taken not to use any plastic accessories when carrying out cryogenic grinding in the knife mills as these could be damaged during the process. Suitable accessories include a grinding container of stainless steel, a full metal knife and a lid with aperture to allow evaporation of the gaseous carbon dioxide.


Large Sample Volumes with Large Feed Sizes in the Cutting Mill SM 300


Large sample volumes up to 4 l with feed sizes up to 80 mm, like a block of 100 g chocolate, 1 kg trout (whole fi sh) or 20 kg potatoes are best processed in the Cutting


Mill SM 300. The use of both LN2 and dry ice is possible. The embrittled sample material is rather hard, therefore the use of the 6-disc rotor is recommended as it works rather like a shredder. It is also suitable to cut heterogeneous samples such as frozen chicken parts including bones. The SM 300 is designed for pre-crushing


Figure 5. Ultra Centrifugal Mill ZM 200


bigger sample pieces <4 mm. Pulverisation of the samples then follows in one of the other mills described above.


Conclusion Figure 4. Bacon before and after grinding in the Knife Mill GRINDOMIX GM 300


Some foodstuff needs to be pulverised under cryogenic conditions, i. e. by using dry ice or liquid nitrogen as grinding aid, to obtain a sample which is suitable for subsequent analysis. Retsch offers a variety of laboratory mills designed for gentle and effi cient cold grinding of food samples which ensure the whole process is time and cost effective. A wide range of accessories helps to make the grinding process safe and user-friendly.


Read, Share and Comment on this Article, visit: www.labmate-online.com/articles ALP for Rapid and Reliable Verifi cation of Milk Pasteurisation Introduced


Hygiena has announced the new ZymoSnap ALP, an innovative alkaline phosphatase (ALP) testing system designed to verify pasteurisation efficiency in short shelf life dairy products within just five minutes. Hygiena’s ZymoSnap ALP has been specifically developed to offer reliable, definitive and repeatable results, even at low levels (25-100 mU/L), ensuring confidence in results. Featuring a convenient all-in-one design and requiring only minimal equipment, the system is simple to use without specialist knowledge or testing facilities. The new ZymoSnap ALP has been independently validated by Campden BRI, the recognised provider of scientific, technical and advisory services to the food, drink and allied industries.


Hygiena’s ZymoSnap ALP has been designed for ease of use and high performance, as well as significant time and cost savings compared with conventional ALP testing methods. For many years, the industry has relied on systems that require high capital and running cost, unstable reagents and positive control leading to wastage and the need for glassware. ZymoSnap ALP overcomes all of these challenges offering a cost-effective solution via convenient disposable devices with a long shelf life. It enables testing to be performed at limits well below the globally recognised regulatory level of 350 mU/L. Utilising Hygiena’s patented snap-valve technology, ZymoSnap ALP provides sensitive and reproducible results, while allowing users to meet their sustainability objectives by being a 100% recyclable test device. ZymoSnap ALP Positive Control Kit provides a reference point at the regulatory limit of liquid milk and validation of other dairy products.


“Manufacturers of dairy products are under constant pressure to demonstrate compliance with international safety and quality requirements. That’s why they need to regularly monitor and verify the efficiency of their pasteurisation process,” said Dr Martin Easter, Chief Scientific Officer, Hygiena. “With this in mind, we have developed ZymoSnap ALP to enable tests to be carried out rapidly allowing for an immediate pass/fail assessment and trend analysis. It has never been easier or quicker to ensure that pasteurisation processes are operating efficiently.”


ZymoSnap ALP is compatible with Hygiena’s multifunctional EnSURE monitoring system, a high-sensitivity luminometer used to detect various indicators and bacteria such as coliform, E. coli and Enterobacteriaceae. Hygiena’s bespoke SureTrend software enables instruments to be programmed and results to be easily analysed and presented.


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