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Prior to the early 1930's most cheese was made from undefined starter cultures; species and strain composition were generally unknown and if known initially would change with each subculture.

Dr Hugh Whitehead and his colleagues at the New Zealand Dairy Research Institute realised that if the dairy industry in that country was to produce close-textured cheese, free from taste and body defects and manufactured within a consistent time period that it would be necessary to use standardised starter cultures. They also realised that they needed to prevent problems arising from the growth of 'wild' lactic acid bacteria and spoilage organisms in the raw milk and introduced pasteurisation of milk for cheese manufacture.

Any agent which inhibits starter activity or kills a strain with an essential function e.g. aroma production can have serious detrimental effects on the quality of the product being produced. Infection with bacteriophage is the major single cause of fermentation failure or of problems in fermentation processes utilising lactic acid bacteria.

The major functions of starters in dairy fermentations are shown in table 1. See the section on starters also.

The infection of a growing bacterial culture with phage is initiated by the adsorption of the phage to the host cell. The specificity of adsorption of lactococcal phages and the location of phage receptor substances have been studied and has been reviewed (Lawrence et. al., 1976).

Lactococcal bacteriophages

Bradley (1967), in a classic review paper, summarised the principles of phage morphology and outlined six basic morphological types (fig. 1). The tailed phages, Bradley's groups A-C account for some 96% of all phages isolated to date and as discussed below belong to the order Caudovirales. Only phages in Group A have contractile tails. All tailed bacteriophages have a nucleic acid core surrounded by a protein coat. Phages active against lactic acid bacteria are approximately tadpole or sperm shaped and have a distinct head terminating in a tail with a hollow core.

Phages attacking lactic acid bacteria belong to Groups A, B and C and contain double stranded DNA. Phages in Groups D and F contain single stranded DNA, however, Group E phages contain single-stranded RNA.

The basic principles of phage control in commercial plants have been known since the early 1940s and the pioneering work of Dr Hugh Whitehead and his colleagues in New Zealand. The review by Whitehead and Hunter (1945)* on the measures that were being used in New Zealand to control slow acid production due to phage infection is still of relevance to factory managers today.

Phage release, the final stage in the phage-life cycle, has been extensively studied and is caused, at least in part, by the action of phage-induced hydrolytic or lytic enzymes.

Because phage lysin has a much broader lytic range than phage, infection of paired and multi-strain cultures with a lysin-producing phage has the potential to cause fermentation failure, dead-vats, and consequent economic loss.

While phage lysin has long been suspected of having an important part in phage lysis it has taken techniques using molecular biology to clarify its in vivo role.

The activity of phage lysins can be determined using several methods; turbidimetry or the determination of the change in concentration of some solubilised cell wall component are frequently used.

 Turbimetry, where a standardised suspension of cells in buffer is mixed with a sample of lysin-containing material is widely used. The lysin causes lysis of the cell suspension and a reduction in optical density (OD). Enzyme activity can be calculated from the decrease in OD with time.

The following method has been found to give satisfactory results (Mullan and Crawford, 1985a).

Cells were suspended in 0.1 M-K phosphate buffer, pH 6.8, to give an OD at 450nm of 0.62-0.75. Depending on the lytic activity, 0.1-1.0 ml of lysin containing solution was added to 5ml of standardized cell suspension at 37°C. After mixing, OD readings were taken at 30 s intervals over a 2-6 min period. Absorption readings were plotted against time and only values on the linear portion of the graphs were used for calculation.

The first stage in the isolation of phage lysin is the production of lysates containing high concentrations of phage. Because lysin concentration is correlated with phage concentration, this objective can be achieved by obtaining lysates containing >1 x 10 10 pfu/ml (Mullan and Crawford, 1985a). Information on the production of high tire phage lysates has been discussed previously. The effects of phage lysin on cells of Lc. lactis c10 is shown below. The lysin rapidly removes the cell walls resulting in cell death.

There are many reasons why information on the concentration of bacteriophage in a sample may be required. These include the determination of:

The double agar method as described by Adams (1959) is widely used to enumerate phages.  In this method a small volume of a dilution of phage suspension and a small quantity of host cells grown to high cell density, sufficient to give 107-108 CFU/ml, are mixed in about 2.5 ml of molten, 'soft' or 'top' agar at 46°-50°C. It is important to avoid over mixing the soft agar since that could result in air bubbles forming in the soft agar and potential misidentification of the bubbles as plaques. The resulting suspension is then poured on to an appropriate 'nutrient' basal agar medium e.g. M17 (Terazaghi and Sandine, 1975) for lactococci to form a thin 'top layer' which hardens and immobilises the bacteria. Refer to figure 1 below.

Abstract

Over 99% of phages detected using microscopy have not been cultured. This article explores factors that influence plaque formation and if addressed may help in phage isolation.

Current data indicate that some 1031 bacteriophages exist globally, including about 108 genotypes. Some phages form very tiny or micro plaques. These can sometimes be so small that it is almost impossible to see them. Frequently 'new' phages can be observed using e.g. electron microscopy under conditions where there is strong evidence of a potential host yet it can be very time consuming or in some instances not possible to get the phage to form plaques. Less than 1% of the phages observed using microscopy have ever been grown in culture, this is sometimes called "the great plaque count anomaly".

Phage activity can also be assessed indirectly by measuring culture activity, the premise being that the presence of disturbing phage will inhibit starter growth.

Several methods are available, and include-

How do you isolate a bacteriophage (phage) and obtain a pure phage preparation? This is achieved by plating a phage suspension using the double agar method, and a susceptible host strain, to obtain plaques and further purifying the phage contained within the plaque.

It is frequently necessary to produce and use high titre phage preparations.

This section provides summary information on the production and storage of high-tire lactococcal phage preparations.

This section contains summary information on modified atmosphere packaging. More comprehensive treatment is available in a chapter on modified atmosphere packaging, written by the author and Derek McDowell, in the book Food Packaging Technology. Derek McDowell is Head of Supply and Packaging at Loughry Campus and is a packaging specialist.

The effect of modified atmosphere packaging (MAP) on dairy products, raw meat, raw poultry , cooked meat and fruit and vegetables is discussed.

Dairy products

 MAP has the potential to increase the shelf life of a number of dairy products.  These include fat-filled milk powders, cheeses and fat spreads.  In general these products spoil due to the development of oxidative rancidity in the case of powders and or the growth of micro-organisms, particularly yeasts and moulds, in the case of cheese.

Whole milk powder is particularly susceptible to the development of off-flavours due to fat oxidation.  Commercially the air is removed under vacuum and replaced with N2 or N2/CO2 mixes and the powder is hermetically sealed in metal cans. 

Introduction

EU regulation 1924/2006 on Nutrition and Health claims made on food was published on 18 January 2007. This is the first piece of scientific legislation to deal with nutrition and health claims and aims to provide a higher level of consumer protection as well as harmonise legislation across the EU to facilitate intra-Community trade.

The regulation will control nutrition and health claims by means of positive lists of authorised claims that can be made on food together with the criteria a product must meet to use them. The annex of the regulation contains the list of permitted nutrition claims and the regulation puts in place processes for the compilation of the list of authorised claims. EU regulations are directly applicable in Member States and this regulation will apply from 1 July 2007.

The purpose of this section is to provide some advice on how the nutrient density or energy content of foods is calculated and displayed on food labels. A calculator is also included to enable students producing new products to calculate the energy density using the chemical constituents of the food. The calculator can also be used as a food calorie calculator.

Food manufacturers in most countries are legally obliged to make several declarations on food labels. The UK Food Standards Agency has a very good overview of labelling from a consumer perspective including an interesting review of public perception of labels .

Summary in Italian

Nel Mondo vi è un elevato numero di bevande ottenute dalla fermentazione alcolica di liquidi zuccherini quali succhi vegetali, miele, latte ecc., ma le più importanti per diffusione e quantità prodotte sono senza dubbio il vino, la birra ed il sidro. Lo scopo di questo breve articolo è quello di riassumere la storia e la tecnologia produttiva di una di queste bevande, ottenuta dalla fermentazione dell'uva, il vino. Conosciuto già dagli Egizi, il vino ha accompagnato con alterne vicende l'uomo in tutta la sua storia, divenendo nella cultura cristiana simbolo, con il pane, dell'unione stessa con Dio. Prodotto in quasi tutto il modo anche in virtù dell'ampio areale di coltivazione dell'uva, il vino si presenta al consumatore in varie tipologie (rosso, bianco, rosato, dolce, secco, spumante ecc.) volte ad interpretare al meglio le caratteristiche della materia prima ed a soddisfare le esigenze del consumatore stesso. Alla base di queste diverse tipologie di prodotti vi sono altrettante tecnologie venutesi a definire nei secoli ed i cui aspetti fondamentali vengono descritti in queste pagine con la speranza di stimolare il lettore ad approfondirne lo studio sui numerosi testi specialistici attualmente disponibili.

Introduction

There is a wide range of alcoholic beverages obtained by the fermentation of sweet liquids (vegetable juices, honey, milk) but the most important are wine, beer and cider. Wine is an alcoholic beverage produced by the fermentation of the juice of fruits, usually grapes, although other fruits such as plum, banana, elderberry or blackcurrant may also be fermented and used to obtain products named "wine". In this short article the word "wine" refers to the product obtained from grapes. This product is probably the most ancient fermented beverage and was mentioned in the Bible and in other documents from Asiatic peoples. Exactly where wine was first made is still unclear. It could have been anywhere in the vast region, stretching from Portugal to Central Asia, where wild grapes grow. However, the first large-scale production of Commercial grape production
wine must have been where grapes were first domesticated, Southern Caucasus and the Near East. In Egypt, wine played an important role in ancient ceremonies and winemaking scenes are represented on tomb walls. Outside Egypt much of the ancient Middle Eastern peoples preferred beer as a daily drink rather than wine. However, wine was well-know especially near the Mediterranean coast and was used in the rituals of the Jewish people. The Greeks introduced wine to Europe and spread the art of grape-growing and winemaking across the Mediterranean hence modern wine culture probably  derives from the ancient Greeks. Wine

was known to both the Minoan and Mycenaean cultures and referred to as "Juice of the Gods". Dionysus was the Greek god of wine and wine was frequently mentioned in Homer's and Aesop's operas. Many of the grapes grown in Greece are grown nowhere else and are similar or identical to varieties grown in ancient times. Greek wine was widely known and exported throughout the Mediterranean basin, and amphorae for Greek wines have been found extensively in this area.

I get lots of queries from companies and individuals either requesting recommendations for people who might be suitable for dairy science, dairy technologist, food technologist jobs or for advice from food job seekers on vacancies in particular job areas. I regret that I can no longer respond directly to these queries, I simply do not have the time to do so.

I will use  this page to  publicise posts connected with the subject areas covered by this site and will consider publicising the details of people searching for work here also. If you wish to advertise a vacancy on this site please use the contact form to discuss your vacancy. Companies placing adverts normally make a small donation towards the running costs of the Dairy Science and Food Technology website or link to this site.  

You can also obtain information about careers and current vacancies in food science and food technology in the links section of this site. I will try to keep these updated and have added a number of  recruitment company links. Note that there is a world wide shortage of food scientists and technologists and that pay and working conditions in many countries now reflect this new reality. Food scientists and technologists with postgraduate qualifications are particularly well paid in the US and the remuneration situation is now improving significantly in the UK, Ireland and in other parts of Europe.

This article provides students with an overview of why employers are increasingly attempting to recruit graduates with entrepreneurial skills. It also explores why economies within the European Union need more people with imagination and drive to think and act in an entrepreneurial manner to create exciting opportunities for themselves and others. Entrepreneurship is not something special that a few people are born with. Entrepreneurship is a way of thinking that can be nurtured in any environment, not just business start-ups but also in existing private and public organisations. Therefore, it is not surprising that schools and colleges are interested in producing more enterprise-savvy graduates; and governments are committed to equipping people with enterprise skills in all walks of life. This article outlines how important it is for everyone to cultivate his or her entrepreneurial spirit.

The Ulster Farmers Union has Insurance and Agriculture Business Opportunities at  Senior Group Manager and Assistant Group Manager level in Northern Ireland.  More information is available at the UFU website.


COMMUNICATIONS OFFICER: 

Based in Belfast., Northern Ireland

Salary:

£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 or download the application form from www.ufuni.org.

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 tonyc@nmr.co.uk), 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 hannah.gilman@vso.org.uk .


 

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  kate_yuxl@hotmail.com

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:

Mr Jaffri's Email address is: Razajaffri@aarknet.com


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 Diane@mkandassoc.com 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.




Technologists producing acidic foods such as pickles and sauces often find it difficult to get information on the processing conditions required to obtain commercial sterility or how to calculate the processing time at a higher temperature. Following the experience of working with processors experiencing technical issues, including spoilage problems and difficulties in exporting products, I have produced a concise Ebook (Thermal processing of acid fruit and vegetable products. Significant microorganisms, recommended processing time / temperatures, and public health significance of spoilage) that may be helpful. Currently the Ebook (figure 1):

Many students have problems in understanding the mathematics describing the destruction of microorganisms by heat. Log reductions of pathogens and equivalent time-temperature treatments along with the associated lethalities account for a large part of the harder to understand topics. The quiz below is a simple test of of some of the basic concepts. Note Z value is not dealt with in this quiz. If there is sufficient interest I will provide the answers.

Heat Processing Quiz

Introduction

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.

Typical pots of UHT milk

Summary

This article investigates how to calculate the lethal effects of UHT treatment and the usefulness of TTIs for differentiating sterilised, direct and indirectly processed UHT-treated milk. The importance of accessing accurate temperature time-data and knowing holding tube dimensions, flow rate, average and minimum holding time and the flow characteristics (Reynolds number) are discussed. The reliability of a model developed by Claeys et al. (2003) to predict the effects of UHT-processing on hydroxymethylfurfural, lactulose and furosine concentrations in milk is discussed. Free On Line calculators for calculating holding time, average flow rate, holding tube length in UHT and HTST plants are provided. A free On Line calculator programmed using the thermal constants calculated by Claeys et al. (2003) is provided to calculate hydroxymethylfurfural, lactulose and furosine concentrations following heat treatment in skim, semi fat and full fat milks. This calculator also calculates F0, B*, C* and % destruction of thiamine. Two methods of numerical integration are used to measure the cumulative lethal and chemical effects of UHT treatment, namely the Trapezoid and Simpson's rules.

Introduction

Typical UHT treatments involve heating milk to 137 to 150 in a continuous-flow process and holding at that temperature for one or more seconds before cooling rapidly to room temperature. The milk is then aseptically packaged to give a product that is stable for several months at ambient temperature.

In Europe, UHT treatment is defined as heating milk in a continuous flow of heat at a high temperature for a short time (not less than 135 °C in combination with a suitable holding time, not less than a second) such that there are no viable microorganisms or spores capable of growing in the treated product when kept in an aseptic closed container at ambient temperature (Reg EC 2074/2005).

Can you destroy Mycobacterium avium subsp. paratuberculosis (MAP) by pasteurization? How important is holding time compared with holding temperature?  Use the powerful free tools in this section to answer these questions.

An article on thermal process modelling has been added. This article calculates the effect of HTST treatment on the number of log reductions of major milk pathogens and discusses the temperature milk should be pasteurized if Mycobacterium avium subsp. paratuberculosis (MAP) was designated as a human pathogen. The log reductions refer to log10 or decimal (10 fold) reductions in the concentration of viable bacteria.

 Effect of HTST treatment on the number of log reductions of major milk pathogens.

 Dry heat sterilisation is widely used for glassware and materials that are not suitable for sterilisation using saturated steam. A range of temperatures and times are used.  Currently a temperature of at least 170°C for 30-60 minutes is widely used. The term is not particularly precise since variable concentrations of water may be present in the oven used (Sandle, 2013).

Spreadsheets for calculating F, B*, C* values of thermal processes and the concentration of Time Temperature Indicators.

Introduction 

DSFT has an extensive range of free-On Line resources for undertaking a wide range of thermal process calculations including dry heat sterilisation (FH) and depyrogenation (FD or FP). This page provides access to a range of Microsoft Excel spreadsheets that can be downloaded for a small donation and will work on a PC or Mac without access to the Internet. In general these spreadsheets are similar to their corresponding free applications on this website.

A number of the spreadsheets have lite or demonstration versions for evaluation prior to purchase. If you want to test a version that does not offer a test version contact me and I can arrange to provide this.

These donations are important. They contribute towards the running costs of the website and enable me to provide free access to the website rather than require a subscription.

MICROSOFT EXCEL LETHAL RATE CALCULATORS AND TEMPERATURE TIME INTEGRATORS FOR THERMAL PROCESSES

Introduction

This section provides the context to using Excel to calculate the cumulative lethal effects (at all stages during processing) of heat on microorganisms and provides an explanation of how the Excel spreadsheets and On Line calculators available for download from the Dairy Science and Food Technology (DSFT) work.

Here we provide an overview of the background, including a summary of the underlying mathematics, required to produce an Excel spreadsheet for performing basic thermal processing calculations. Note I am not providing a guide to using spreadsheets but basic information that a competent Excel user should be able to use to make their own thermal processing spreadsheet.

Download Excel Thermal Processing Spreadsheets.

The Dairy Science and Food Technology website contains several free, On Line calculators, for determing the cumulative lethality (F, B*, P or PU) of thermal processes, the concentration of Thermal Process Indicators (TTI) following UHT treatment of milk and several other process indicators.

These calculators are listed on the Calculators and Models page under Thermal Processing e.g.

The lethality calculators convert temperature readings to lethal rates, plot the lethal rates against time, and determine appropriate lethality values or chemical indicators for a heat process whether using hot water, saturated steam or dry heat. The area under the time-lethality curve is determined by numerical integration using the industry standard method, the trapezoid rule or the more accurate Simpson's rules or both for comparitive purposes. In general the more values, the more accurate the value for F or P will be. One of the calculators will also upload CSV files of a thermal process and provides a facility for free, independent validation of a thermal process.

DSFT provides a range of thermal processing consultancy services to food and pharmaceutical manufacturers. These include:

  • Independent validation of the antimicrobial effectiveness of the heat treatments used in processing.
  • Calculation of the average holding time used in processing HTST and HHST products.
  • Determination of the flow type and calculation of the minimum holding or residence time of the fastest flowing particles in HTST and HHST products.
  • Determination of the F values and the number of logarithmic (log10) reductions of designated microorganisms following heat treatment.
  • Advice on equivalent heat processes to meet legislative and other requirements.
  • Benchmarking of company processes against statutory and international best practice.
  • Advice on alternative methods to microbiological examination for providing additional assurance of adequate heat treatment e.g. the phosphatase test is of no value in providing assurance that a temperature >80°C was used in milk processing. Additional tests that confirm higher temperatures than e.g. normal milk-pasteurization temperatures can be provided. The merits of incorporating these into routine quality assurance testing will be explained.

Small, and even large companies, frequently find it difficult to contact potential new supplier or service partners. This is a particular problem for some small companies attempting to operate testing laboratories.

However, there are companies who provide exemplary customer service and work hard to meet customer needs. The following is a list of these companies that provide exemplary customer service in the laboratory service area.

The nature of polyphosphate

Inorganic polyphosphate (polyP) is a linear, unbranched polymer of orthophosphate residues linked by phosphoanhydride bonds (Figure 1.1).  PolyP ranges in size from three to over one thousand orthophosphate residues (Kornberg et al., 1999).  PolyP is widespread in bacteria and yeasts and has been found in plant and animal cells (polyP is also formed by dehydration and condensation of phosphate at the elevated temperatures of benthic and volcanic vents (Kornberg et al., 1999).

Linear structure of polyphosphate
PolyP was first found in yeast cells by Liebermann (1888). Further work by Wiame (1947), Kornberg (1956) and others through the 1940s and 1950s established the role of polyP, or 'volutin' as it was then known in the accumulation of phosphate and in energy storage by microorganisms. PolyP was observed in many microorganisms as metachromatic particles and was historically used as a diagnostic tool for certain pathogens such as Corynebacterium diphtheriae (Robinson & Wood, 1986). PolyP, like other anions, shifts the absorption of basic dyes such as toluidine blue, to a shorter wavelength (630 to 530nm) therefore giving rise to a metachromatic effect. When viewed by electron microscopy intracellular polyP appears as dark, electron dense granules. The presence of polyP in cells may also be detected by other techniques such as 31P-NMR analysis (Glonek et al., 1971) and by fluorescence of 4-6-diamidino-2-phenylindole (DAPI) (Allan & Miller, 1980).

The articles on the Lactoperoxidase system by Michael Mullan include material produced with former colleagues, in particular Professor Lennart Bjorck (SE), Dr Ir. J Stadhouders (NL) and Professor Dr W Heeschen (DE), on International Dairy Federation Group IDF F19, 'Indigenous antimicrobial proteins in milk'.

The work of the group was initially focused, after a request in 1982 from the Joint FAO/WHO Committee of Government Experts for technical advice from IDF on the use of the lactoperoxidase system for preservation of raw milk. This work resulted in a "Code of Practice", which was published in 1988 (Bulletin of IDF No. 234/1988).

 In the 1985, IDF through Group F 19 "Indigenous antimicrobial proteins in milk" working in collaboration with the Federation of European Microbial Societies (FEMS) organised a symposium titled "Antimicrobial systems in milk".

The author presented a paper on behalf of the Group entitled"Significance of the Antimicrobial Proteins of Milk to the Dairy Industry" at the IDF Cheese Week at Rennes, France 1988. This draft Django platform.document formed the basis of a more extensive monograph entitled the 'Significance of the indigenous antimicrobial agents of milk to the dairy industry' published by IDF in 1991 (IDF bulletin . 264/1991). More recently a monograph,'Determination of indigenous antimicrobial proteins of milk' (IDF No. 284/1993), detailing methods for the analysis of these antimicrobial proteins in milk was published.

Michael Mullan also gratefully acknowledges collaborative work with former colleagues Dr Bob Crawford (deceased), Dr Bo Ekstrand, Dr Nigel Wade, Dr Tony Waterhouse and the late Mr Arthur Walker at the WSAC at Auchincruive. The WSAC is now part of the SRUC.

The animal feeding trials at Auchincruive were led by Dr Tony Waterhouse. Studies on the production of lactoperoxidase containing feeding materials and the development of a milk replacer containing a stable and functional lactoperoxidase system were led by the author. Michael Mullan gratefully acknowledges the detailed biochemical work by Dr Bo Ekstrand that was critical to these developments and the excellent scientific support work undertaken by Margaret McDougall and Marion Muir. Bo Ekstrand's post doctoral research was funded by Astra-Ewos. The low heat skim milk powder that formed the lactoperoxidase source for the milk replacer was produced in collaboration with Mr John Hynd, the manager of the Scottish Milk Marketing Board creamery at Stranraer in Scotland.

Arthur Walker died in 2002. Arthur was a person dedicated to the education of young people and had an extraordinary positive attitude to life. He isolated many of the bacteriophages that were in the Auchincruive phage collection when I went to Scotland in 1977. Most of these had been isolated from technical investigations of slow-acid problems with single-strain starters such as C2 at the then SMB factories at Stranraer and Dalbeattie. Hence my designation of the C2 phage that I studied as part of my PhD, as ØC2(W).

Some of the work on phage enumeration discussed by Michael Mullan was undertaken at University College Cork, Ireland working with Professors Charlie Daly and Pat Fox. Their generous help and advice over many years is gratefully acknowledged.

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Dairy Science and Food Technology website

 

This article explains how to convert numbers to scientific notation and back again to standard format. It also contains two calculators that will enable calculations to be checked and that provide feedback on common data entry input errors.  

How do you convert numbers to scientific notation?

In mathematics, science and engineering students frequent have to work with very small, e.g. 0.000005, and very large, e.g. 3200000000 numbers. For example, students in microbiology are often required to write the number of colony forming units (CFU)/mL or gram in scientific notation. To avoid dealing with these large and small numbers mathematicians, scientists and engineers have developed a particular way of expressing numbers; this is called scientific notation.

There are a range of formulae that can be used to assess the readability of written text.  While these all have limitations, judicious use of several ‘readability' predictors can improve the clarity of writing of articles, theses, reports and assignments.

The software used here, an online readability calculator, will return a number of indicators including the average words per sentence, Fog index, Flesch reading ease score, and Flesch-Kincaid grade level. These readability indicators may be of help in editing and developing your written work.

It is unclear how useful computer programmes are for analysing scientific writing since the language used tends to be complex. However, some studies have shown that the indicators derived using the software here do have value.

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.

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