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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.
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).
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.
Characteristics - Cevrin di Coazze is a ripened cheese produced from a mixture of goats' and cows' milk. The concentration of cows' milk must be 60-70%. Cevrin di Coazze cheese is cylindrical with flat surfaces. The cylindrical shape has a diameter of 15-18 cm, an edge of 7-10 cm and a weight of 800-1500 g. Ripening lasts at least 20 days but is frequently longer than 120 days. The crust is smooth and regular but not elastic. The colour is wrinkled, hard, and reddish-grey with yellow and white highlights depending on its age. The dough is yellowish with small and sparse holes. The texture is soft and elastic. The odour is strong and persistent. The taste is very savoury and mainly hot, salty and acid in ripened products.
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.
Characteristics of Listeria monocytogenes
DSFT provides a range of consultancy services to ice cream, gelato, sherbet and sorbet manufacturers. These range from help in formulating recipes, reducing costs by replacing expensive imported additives, problem solving, courses in advanced product manufacture, advice on all aspects of HACCP including process validation, providing assistance in discussions with regulatory authorities to independent audits of plant, process and external advice received. Independent nutritional advice on the manufacture and safety of low or sugar-free gelato and ice cream products is also provided.
We can help with the development and commercial production of soya and dairy-free, high protein ice cream-like products with or without sucrose. There are better options than sorbitol and fructose. Science based advice on describing products intended for consumers with health issues can also be provided.
Despite work undertaken over 20-years ago by researchers in Canada many large scale ice cream producers have limited knowledge of the minimum holding time of ice cream mix processed using HTST or HHST heat-processes. Furthermore many lack the evidence that they meet regulatory requirements for holding time. DFST can use your plant data to calculate average holding time, flow type, minimum residence or holding time, the log reductions of major pathogens and advise on any remedial action required.
Note this article is still in draft form and is available On Line to facilitate editing. It is scheduled to be completed by June 2015.
PHP has become particularly popular and is fairly easy to learn. Classic ASP is very easy to learn but is increasingly being replaced by ASP.NET. Virtually anyone who can put a spreadsheet together is capable of learning a basic language such as ASP.
The purpose of this article is to show how the calculator for predicting salmonella growth on tomatoes was written in ASP. I would like to encourage lecturers and students to learn how to programme. While ASP is being replaced by ASP.NET the basic premises using in ASP coding can be applied to other languages and even if you decide to learn PHP which is a particularly versatile web language you will be able to apply the concepts learned
Constructing the data entry form
The HTML and ASP code used to construct the data entry form is shown below. For simplicity web page header information, value information in ASP and some form security information has not been shown.
The input form was constructed by writing the code for a table in HTML and adding in HTML text boxes to allow initial number (no), temperature (t) and incubation time (hr) to be entered.
<form id="form1" name="form1" method="post" action="sam1.asp">
<table width="75%" border="1" cellspacing="0" cellpadding="1">
<th colspan="2" scope="col">Predict the growth of salmonella in cut tomatoes at 10°C to 35°C</th>
<td width="41%">Initial number of salmonella / gram</td>
<td width="59%"><input name="no" type="text" id="no" value="<%=no%>" /></td>
<td><input name="t" type="text" id="t" value="<%=t%>" /></td>
<td height="20">Incubation time, hours</td>
<td><input name="hr" type="text" id="hr" value="<%=hr%>" /></td>
<td height="20" colspan="2"><div align="center">
<input type="submit" name="Predict number of samonella" id="Predict number of samonella" value="Predict number of salmonella" />
Writing the data processing script
A simplified version of the processing script is given below. The notes which are preceded by a ' explain how the script works.
<% Option Explicit
'Use of option explicit will ensure that error messages are displayed if there are coding problems. These are helpful in finding solutions. %>
'no, t and hr are values that have been entered on the form
'r,g,gen, pop are the products of calculations that will be undertaken
'We will now obtain the information from the entry form to perform the calculation
'Taking information from the form we will calculate r,g, gen and pop. This could easily be done in one calculation. The calculation has been broken down into its component parts so that it can be followed more easily.
'For an explanation of the calculation please see http://www.dairyscience.info/index.php/food-model/258-predict.html
g=1/(r*r) 'note r is the square root of the growth rate, we need to obtain the growth rate by multiplying r by r
pop = no*2^gen
'We next need to provide the results of the calculation for pop which is the total number of salmonella after growth at the temperature chosen for the time inputted.
If t >9.99 AND t <35.01 THEN ' basic validation to ensure that the results are within the temperature parameters modelled
'The 'If Statement' is used to make a decision to execute code if some condition is True.
response.write ("The predicted number of samonella after" & " " & (hr)& " " & "hours has been calculated as" & " " & round(pop,0) & " " & "CFU/g.")
'END IF is used to indicate the end of code execution
IF t < 10 THEN
Response.Write (" Caution. This model as not been validated at temperatures <10°C.")
IF t > 35 THEN
Response.Write (" Caution. This model as not been validated at temperatures >35°C")
About the data processing script
To be added.
I learned ASP, how to use Access Databases and HTML from a former colleague Dr Raymond Martin. Raymond generously helped me correct concatenation and many other errors and though his help I gradually learned how to write quite sophisticated data-base driven ASP applications. I gratefully acknowledge Raymond's help over many years.
How to cite this article
Mullan, W.M.A. (2015). [On-line]. Available from: https://www.dairyscience.info/index.php/cheese-starters/209-articles.html?start=80 . Accessed: 11 December, 2019.