The calculator below is based on a model developed by Giles and Lawrence (1973) to predict the grade value of Cheddar cheese. Instructions on how to use the calculator are given below. Note that the pH and other values should be obtained from 24-hour old cheese.

If you are submitting assignments, essays or theses then you are required to correctly reference any ideas, images, data, reference lists you have used which are not your own. This also includes data and information you have obtained from electronic sources including the Internet.

Failure to give credit to the work of others can result in you being accused of plagiarism which if proven could result in no marks being given for your work or suspension from your course or even expulsion from your College or university.

The Ulster Farmers Union has Insurance and Agriculture Business Opportunities at  Senior Group Manager and Assistant Group Manager level in Northern Ireland.


Based in Belfast., Northern Ireland


£19,028 - £29,597; commensurate with experience.

The Ulster Farmers' Union, Northern Ireland's leading farming organization, wishes to appoint a Communications Officer.

Working in the UFU Membership and Communications Department, main duties and responsibilities will include: working effectively and efficiently in a dynamic team environment to produce news releases and publications; building and maintaining good relations with the media; developing the UFU Website and E-communications; and coordinating the UFU presence at events such as the Balmoral Show.

This is an exciting opportunity to work in a very busy, diverse and rewarding environment.

So if you have a commitment to the local agriculture industry, a demonstrable interest in press/public relations, have strong ICT skills and possess a third level qualification in an agriculture related subject, then contact the Ulster Farmers' Union for full details and an application form. Tel: 02890 370222.

The closing date for receipt of applications is Friday 30 July 2010 at 12 noon.

The Ulster Farmers' Union is an equal opportunities employer and welcomes applicants regardless of religious belief, political opinion, sex or marital status.



National Milk Recording (NMR) logo

National Milk Laboratories (a subsidiary of National Milk Records plc) provide milk testing services to the GB dairy industry, not only undertaking milk payment testing for circa 95% of all dairy farms, but also offering microbiological and disease testing services to help our farmers and milk buyer customers produce high quality milk and products for the consumer.

Due to retirement, a vacancy for a Laboratory Manager has arisen at our Kelvin Avenue, Hillington, Glasgow laboratory. The successful job holder will be expected to take responsibility for all aspects of laboratory operations which operate 20 hours / day, 365 days / year. You will need to demonstrate strong technical and staff management skills, along with business awareness and confidence in order to represent the NML business to existing and potential customers. The ability to apply technical knowledge to improve the efficiency and effectiveness of existing service provision as well as facilitating the introduction of new testing services will be important aspects of the role.

Applications are invited from candidates who possess the skills and aptitude to fulfil this important role within NML. Please apply in writing, enclosing your CV to Tony Craven, NMR Group Operations Manager, National Milk Records, Skipton Road, Harrogate, North Yorkshire, HG1 4LG (post or e mail to, stating why you feel you are the person most suited to this role. If you require further information, Tony can be contacted on 01423 851350. Closing date 9th April 2010.




Cheese and Dairy Processing Advisor with The Women’s Association ZamZam, Tajikistan.

What’s the context and purpose of the role?

Tajikistan is a poor country, where most of the people live below the poverty line, particularly in rural areas. ZamZam was established in 2006 with the aim of creating income generating activities for poor women living in the Muminabad district of Tajikistan. A project was set up to produce and process dairy products and you’ll work with the staff of ZamZam to increase the reach of this project and extend the range of products. This placement will give you scope to get involved in all areas of the production and marketing of milk and cheese, with the goal of improving product sales. By allowing these vulnerable women to process and sell dairy products, you’ll enable them to earn a living and access better health and education for their families.

What does the role involve?

  1. Advising around 30 women on milk storage to improve the shelf life of products.
  2. Providing technical training (composition of milk product, chemical and biological components) to improve the quality of produce.
  3. Recommending dairy products to diversify current output.
  4. Training women at ZamZam on cheese production.
  5. Developing packaging and labeling of products.
  6. Reviewing current practices and recommending ways to increase milk production.

What skills, experience and personal qualities are needed for the role?

You’ll have a minimum of 5 years’ experience working in a hands-on role in cheese and dairy production. Ideally you’ll have experience of small-scale production and will be familiar with packaging and marketing of dairy products. You’ll be able to train others in basic computer skills (excel and word) and will be comfortable working with and training a wide range of people through the help of an interpreter. 
You’ll be able to show initiative and work with little supervision. Finally the ability to work effectively with limited resources and retain a positive and flexible approach is a must for VSO volunteers, as is a good sense of humour!

And the rest…

You’ll be living and working in Muninabad District, in the Southwest of Tajikistan (part of the Kathlon Province). People in the area are mainly involved in agricultural work such as growing wheat and potatoes or raising livestock. Kulyab, 40kms away, is a bigger city with a railway and international airport. The region has a temperate climate with cold winters, warm summers and little rainfall from July – October. There are no safety concerns and locals are hospitable and welcoming to foreigners. A willingness to learn basic Tajik will come in useful and the effort shown in learning their language is very much appreciate by the Tajiks. However you will also be provided with an interpreter.

This is a short-term volunteering position for 6-months. In return, you will be  provided  with valuable training before your placement, a local salary, return flights, accommodation and insurance. When you return to your home country, VSO will help you to resettle and we’ll invite you to stay involved with us through campaigning, development awareness raising and fundraising.

For more information contact Hannah Gilman .

A Dairy Quality Control Advisor at Lilongwe Dairy, Malawi added 29 January 2009.

What’s the context and purpose of the role?

Lilongwe Dairy provides a living for many smallholder dairy farmers; however the income it generates is greatly affected by the poor quality of its output. You’ll be working at the dairy to improve the quality of the raw milk entering the dairy from the producer groups. By reducing the losses to the producers from rejected sour milk and improving the quality of the product coming out of the dairy, you’ll help to reduce overhead costs and improve the farmers’ confidence in their product. As a result of increased sales and increased profitability to the processor, higher prices can be paid to the producers for their milk without increasing the cost to the consumer. You’ll directly benefit both the dairy farmers and the producers by sharing your experience and skills in milk processing.

Quality Control Advisor at Lilongwe Dairy, Malawi What does the role involve?

•   Improving the overall quality of raw milk entering the dairy.

•  Improving the quality of the milk products at Lilongwe Dairy.

•   Training colleagues in technical aspects of Quality Assurance.

•  Providing a training plan for improved hygiene, testing, handling and storage of milk.

•  Creatnig inspection and sampling plans for raw materials packaging materials and finished products.

What skills, experience and personal qualities are needed for the role?

You’ll have several years’ experience working in the Dairy sector, specifically in quality control. You’ll be able to create quality control inspection and testing plans and also be confident in training others to undertake and analyse tests on raw milk. You’ll be working with few resources, so it’s essential to make inventive use of what’s already there. You’ll need a positive outlook and an ability to work with a wide range of people in solving problems. By involving the staff members in decisions, you’ll find it easier to make changes, so an outgoing nature will be very useful.

And the rest…

You’ll be working in the capital Lilongwe and will probably be living in a VSO guesthouse near the City Centre. The city is very sociable with many other expats and about 20 VSO volunteers living there. This ensures that there’s a fairly busy social side to life as a volunteer. There are art galleries, restaurants and shops, but Lilongwe is also a very green and calm city. From Lilongwe it is possible to visit the rest of Malawi’s beautiful countryside and nature reserves.

Well ask you to commit 12-24 months to make a sustainable contribution to our development goals. In return, well give you comprehensive financial, personal and professional support. We'll provide you with extensive training before your placement, and our financial package includes a local salary, return flights, accommodation, insurance and more. When you return to your home country, VSO will help you to resettle and many of our returned volunteers stay involved with us long after their placement ends.

For more information contact Hannah Gilman at .


Dairy scientist added 20 November, 2007. 

Kate Yuxl from the ChinaClick2 Group is seeking to recruit an experienced dairy scientist. Details of the vacancy are given below.

This is an excellent opportunity to join an established dairy  company. Our clients are a leading China dairy manufacturer. Currently, they require an leader with experience and understanding of product development to join their technical research team. Their research centre is located in Europe. 

Within this role your key responsibilities will include significant input into new product research. Working within the team, you will also need to routinely communicate effectively and efficiently with other departments, providing technical expertise when required. 

The successful candidate will ideally possess the following attributes: 

• Tertiary qualification in Dairy Technology/Science or similar ;
• 10 or more years practical dairy product development experience; 
• The ability to apply technical and analytical techniques;
• A proven ability to complete projects within tight deadlines; 
• Excellent communication and organisational skills; 
• Able to work as leader of a team.

This is an excellent opportunity for someone looking to get into Dairy Development with a progressive organisation. For a confidential enquiry or to apply for this position please email

Note: If this vacancy is not exactly what you are seeking, then please contact me in confidence to discuss your individual requirements.


Dairy technologist added 24 April, 2007. The post below has been filled. 

Raza Jaffri from the Dubai-based international headhunting firm, Mosaic Search, is seeking to to recruit a Dairy Technologist experienced in Buffalo Milk product development. Their client is one of Pakistan's largest chemical and fertilizer producers. They have recently diversified into the food business with the launch of highly successful brands in the milk category. A modern milk processing facility has been established and the company is already in the process of setting up another plant to meet expanding consumer demands. 

Key to their ongoing success is the recruitment of a Head of Product Development who will develop and build a recipe bank of milk products. The person appointed will report to the Head of Manufacturing and Supply Chain Director. 

The ideal candidate will have a Masters degree (preferred) in dairy technology coupled with at least 15-20 years experience in developing dairy recipes with buffalo milk with a strong emphasis on powdered milk. 
For more information please contact:


Cheese maker added 15 April, 2007.

M.K. and Associates, Inc. wish to recruit a talented cheese maker to join a rapidly growing company. The cheese maker must have knowledge of dairy processes.  The successful candidate will work as part of a team to create and expand upon an existing product line of natural cheeses and cultured dairy products. This is an opportunity to introduce new cheeses on a national level. Salary $45K. Must be a US resident or citizen.

Applicants should have a B.S. in Dairy, Food Science, Chemistry or related area. However, understanding of cultured dairy products and dairy processes is as important.

Please contact for additional information or call (724) 285-7474.

CPL Executive Search are searching for a scientist qualified to PhD level in Biochemistry, Microbiology or Nutrition, particularly in areas relating to Food, Nutraceuticals or Health.

 The salary pays up to £40k and the post is located in Wales in the UK. Details removed.

There is increasing interest in farmhouse cheese making in the UK and Ireland and Jongia (UK) Ltd., a supplier of equipment and ingredients to the UK and Irish dairy industry, offers study tours to German dairies. These study tours offer existing and potential new businesses an opportunity to see equipment in action and to discuss cheese production and marketing with farmhouse producers.

The study tours are offered as intensive one or two day trip, depending on flights and and are planned to be low cost.

Study tours take place in the spring and autumn each year.  Participants can select from 3- routes, each with a different accent for a different market. Many cheese makers have joined all of the trips, even a few coming twice! Participants have included seasoned cheese makers, novices and hobbyists.


Berlin area, 3 - 4 dairies, with the accent on fresh products, like drinking milk, yoghurt, curd cheese (quark) and soft cheese. Two of the dairies are organic (one bio-dynamic) and one is goat milk dairy. Depending on flights we can execute this as a day trip

Westpahlia (Dortmund area), 5 or more dairies. The accent is on Gouda/Edam type cheese and curd cheese (quark).

Bavaria/Austria border. 4 dairies with the accent on soft cheese and mountain cheese. The latter is an Edam type process with a red smear coating.

Our participants are always very enthusiastic after the trips, having not only seen new ways to solve problems they might have, but also having made new contacts and friends. All have indicated that the interactions with the other participants were an important part of each study tour.

Examples of  technology and developments seen on study tours

The Westphalia trip visits exclusively cheese makers who are also farmers and run farm shops as well, while a few also run restaurants. These farmers are now entrepreneurs of the first degree and are eager to share their experience with us. Images of a dairy shop are given in plates 1-3 below.


 Exterior of farm dairy shop at Thomashof in Burscheid


Mr Jaap de JongeMr Jaap de Jonge works for Jongia (UK) Ltd. After studying food technology in the Netherlands, Jaap de Jonge worked at two dairies in the Middle-East in the mid eighties. Following his experience in production he worked in sales positions selling ingredients in the Middle-East with sales offices in Istanbul, Turkey and Birmingham, UK.  In 2000 he launched Jongia (UK) Ltd. as a representative office, promoting European suppliers who supply equipment and ingredients to the UK and Irish dairy industry. Products include cheese making equipment, soft cheese wrapping, cheese cultures, natural rennet and much more. In addition Jongia (UK) Ltd organise regular tours to German farm house cheese makers and more recently Dairy Seminars.



Modelling the spoilage of pasteurized milk

Spoilage of pasteurized milk is almost always due to the growth of microorganisms. These are generally introduced after heat treatment and are referred to as post process contaminants (PPCs).

The shelf life of pasteurized milk is largely dependent on the number of PPCs and storage temperature (e.g. Muir, 1996). Muir (1996) has described a simple equation (equation 1) relating the number of number of PPCs and storage temperature to shelf life of pasteurised milk.

Equation 1. Shelf life (h)={0.00621*(T+273-(269.55-0.74))*(CFC15)-0.11 x ( CFC15) x 2} -2.

Where T = storage temperature in °K; CFC15, =log10 count after pre-incubation of pasteurized milk at 15°C for 24 hours enumeration on milk agar containing a selective supplement for pseudomonads called cetrimide-fucidincephaloridine (CFC).

Muir (1996) has explained that the equation can predict shelf life at storage temperatures between 6°C and 14°C to within 1 day for between 60 and 90% of samples. The accuracy of the equation has been reported to increase as the storage temperature of the pasteurized milk increases.

Go to Shelf Life of Pasteurized Milk Calculator .

Literature cited
Muir, D.D. (1996) The shelf-life of dairy products: 2. Raw milk and fresh products. Journal of the Society of Dairy Technology. 49, 44-48.

How to cite this article

Mullan, W.M.A. (2015). [On-line]. Available from: . Accessed: 26 September, 2022.  

Help for lethal rate calculator

How does the calculator work? The calculator converts temperature readings to lethal rates, plots the lethal rates against time, and determines the F values for the overall heat-process. The area under the curve is determined using the industry standard method, the Trapezoid rule. The calculator is capable of giving accurate F determinations for most thermal processes. In general the more values, and the smaller the time interval between the values, the more accurate the value for F will be.

Lethal rate is calculated using the formula, lethal rate= 10 (T-Tr/Z) where T is the temperature, in Celsius, at which the lethal rate is required and Tr is the reference temperature. Note lethal rate is a relative term that compares the microbial killing effect at a measured temperature to one minute at the reference temperature.

Tr will vary on whether Fo is being calculated or whether a pasteurisation process or other heat treatment is being assessed. A Tr of 121.1° C is used in the determination of Fo. If F70 or other F value is required then Tr must be set to 70° C or other temperature.

The Z-value, is measured in °C, and is the reciprocal of the slope of the thermal death curve for the target microorganism or spore; 10° C is the value frequently used in Fo calculations performed on low acid foods. Users can vary the Z-value depending on the target organism being considered. The Z-value has a significant effect on the F value of a process. Note it is the decimal reduction value, D, that is a measure of the resistance of a microorganism to heat. The z-value provides information on howthis heat resistance changes with temperature. The effect of the Z-value can be seen in the free lethal rate tables that can be downloaded from here.

Tr can be varied by the user. 

Using the calculator

The Reference Temperature and the Z values should be set first. Next the data grid for entering data is produced.

The starting time e.g. 2 minutes from the beginning of heating and the final time e.g. 180 minutes from the start of heating should be set. The time interval between the temperature readings (∆t) must also be set e.g. 0.1 minutes. Once this information has been set, the user should press the “New data grid” button to create a data entry table. Temperature values are entered using the edit control.

The application can be tested using internal test data. This data when used with the set values should give a Fo value of 8.43. You may also change the Tr or Z values once the data has been loaded and use the “Recalculate button” to investigate the effects of changing these variables on the F values generated by your dataset.

Uploading a csv file

Instead of creating a new data grid to enter time and temperature data you can upload a text file containing your data and the application will determine the F value. If you want to use a different Tr or Z value you should set the Tr-value after you have uploaded the data and then use the Recalculate button to determine the F value. The data must be submitted as a comma separated value (CSV) text file. Use a '.' and not a ‘,’ as the decimal separator. The file must have the extension “.csv”.

A csv file looks like:

Time, Temperature

and can be generated using a spreadsheet programme, if you do not want to prepare the data manually. While a csv file will enable users to use actual values, and will work with uneven time intervals, the use of uneven time (t) intervals is not recommended; keep the ∆t constant! Numerical integration (this is what we are actually doing) using the Trapezoid rule gives more accurate results when even time intervals are used.

Note. When a .csv file is imported the data in the table and on the chart will change to reflect the new values entered. Once this data has been entered you can vary the Tr and z-values and use the recalculate button to calculate a new F value.

The number of log cycles that a designated microbial population has been reduced can be calculated by dividing the F value by the D value at Tr. A 12 log cycle reduction is required for spores of Clostridium botulinum in 'commercially sterile' low acid canned foods.

Please post any queries in the forum.

You can also download Excel spreadsheets to calculate F values.

Return to lethal rate calculator

See survivor probability calculator

How to cite this article

Mullan, W.M.A. (2008). [On-line]. Available from: . Accessed: 26 September, 2022. Updated 2010, 2015, 2017. 


There will be occasions when a food manufacturer wishes to use a different, but equivalent lethal thermal process. How does the processor calculate the equivalent process?

This article explains how to calculate an equivalent thermal or heat process at a higher or lower temperature and provides access to a free On Line calculator for checking your calculations.

Providing that the F value at Tref and the z value are known then the F value at the required temperature, T, can be calculated using equation 1.

Equation 1.  


Equation 1 has been derived from Stumbo (1973).


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