Heat treatments for raw milk

1. HEAT TREATMENTS FOR MILK
Presented By:- Sourabh Kale
M. Tech. (Dairy Technology)
SMC, College of dairy science, AAU, Anand.

2. Content:-
Introduction
Commonly used heat treatments
 Thermization
 Stassanization
 Pasteurization
 Batch Sterilization
 UHT Treatment
 High Pasteurization (ESL)
Heat treatments for specific dairy products.

3.  After the introduction of pasteurization (Batch method -1885), heat
treatment of milk has attracted a huge amount of research attention.
 Any intentional heating above 50 ° C for a sufficient time such that
there is a reduction in the concentration of one or more microorganisms
is considered as heat treatment. (IDF Factsheet, 2018)
 Thus, the heat treatment concept covers an infinite number of
combinations of time and temperature.
 The treatments can be categorized into those used for milk for direct
consumption and those used for specific dairy products.
Introduction

4. Thermization
 Thermization is a generic description of a range of sub pasteurization
heat treatments (57 to 68°C for 15 s) that markedly reduce the number
of spoilage bacteria in milk with minimal heat damage.
 Thermization is a heat treatment applied to raw milk aimed at reducing
the number of organisms in milk and permitting longer storage of the
milk prior to further processing. The heating conditions are 62 to 65 °C
for 15 to 20 seconds. Thermized milk must be phosphatase
positive(CAC, 1999).
 Destruction of some non-spore forming pathogens and psychrotrophic
spoilage bacteria.

5. Stassanization
 Henri Stassano invented it in France.
 This method of pasteurization is carried out in a tubular heat
exchanger consisting of three concentric tubes.
 Passing milk between two water-heated pipes through the narrow
space of 0.6 to 0.8 mm.
 The milk is heated to about 74 ° c for 7 sec. and then promptly
cooled

6. Pasteurization
 According to FSSAI and Codex- Pasteurization, Pasteurized and similar
terms means a microbicidal heat treatment aimed at reducing the
number of any pathogenic micro-organisms in milk and liquid milk
products, if present, to a level at which they do not constitute a
significant health hazard.
 Pasteurization conditions shall be designed to effectively destroy the
organisms Mycobacterium tuberculosis and Coxiella burnettii.
 By LTLT or HTST and cooling it immediately to a temperature of 4 °C or
less.
 Phosphatase test should negative.

7. Pasteurisation Unit (PU)
 One PU results from heating at a temperature of 60 °C (140 °F) for 1
min. The equivalent. z-value is 10 °C (18 °F), which is high for
vegetative bacteria. Thus, the number of pasteurization units for a
heating temperature (T,°C) and heating time (t, min) is given by ;
 63 °C for 30 min would have a value of approximately 60 PU,
whereas HTST conditions (72 °C/15 s; originally 161 °F or 71.7
°C/15 s)would give only 3.96 PU (Wilbey, 1993).
 pasteurization destroys neither the spores nor the toxins secreted
in the milk by organisms that lived in it prior to its heat treatment.

8. Sterilization
 Referred to in-container batch wise heating process.
 According to FSSAI Sterilization when used in association with milk
or milk products, shall be taken to refer to the typical process of
heating milk or milk product in sealed containers continuously to at
least 115ºC for 15 minutes to ensure preservation at room
temperature for a period not less than thirty days from the date of
manufacture.
 Codex guidelines suggest using minimum temperature-time
conditions which achieve an Fo value of 3 min.

9.  The temperatures for sterilization are in the range 110 to 125°C in
combination with appropriate holding times such as 121°C for 3
minutes or 115°C for 13 minutes.
 Turbidity test should be negative.
 12 log reduction of Cl. Botulinum is essential.

10. UHT treatment
 UHT treatment referred to high-temperature/short-time heat treatment
aimed at producing a commercially sterile product which can be
stored at room temperature.
 According to FSSAI, UHT refers to the process of heating milk or milk
product to at least 135ºC for one second or more in a continuous
flow and then packing under aseptic condition in hermetically sealed
containers to ensure preservation at room temperature for a period of
not less than fifteen days from the date of manufacture.

11.  The total heat treatment is equivalent, in terms of its effectiveness
against heat-resistant bacterial spores, to a minimum Fo value of 3
min.
 The main requirement is to reduce spores of Cl . Botulinum.
 Reduction of B. stearothermophilus to minimum 2 log is
considered to be good .
 Turbidity test is positive.
 UHT-treated milk and cream are packaged aseptically into
sterilized, hermetically sealed containers.

12. High Pasteurization
 It is a continuous heat treatment between HTST pasteurization and UHT
sterilization, and is used to produce extended shelf life (ESL) milk.
 An exact, generally accepted definition of the term ESL milk with regard
to shelf life does not yet exist.
 EU legislation (EU, 1992) states that pasteurized milk, which shows a
negative reaction to the peroxidase test, must be labelled ‘high
temperature pasteurized milk’.

13.  Treatment is carried out at 120 - 135°C for 1-4 sec
 The combination of microfiltration(average pore size of 1.4 μm) and
pasteurization has proved to be a very efficient way to produce ESL
milk (Hoffmann et al., 1996).
 Commercial ESL milk has a shelf life varying from 30 to 90 days at
4°C.
 Low original bacterial count in the raw milk is recommended. A
microbial count of 100,000 cfu should not be exceeded
(TeGiffel et al., 2005).

14. Comparison
(Ozer and Akdemir - Evrendilek, 2014)

15. Innovative steam injection(ISI)
 To overcome problems which are inherently present in UHT milk and to reduce the
appreciable amount of denaturation of whey proteins, the Innovative Steam Injection (ISI) is
introduced.
 very short heating is combined with very high temperatures: less than 0.1 s at 150–200°C
 The heating is directly followed by flash cooling in a vacuum vessel.
 The process costs of the ISI technology are some 10% higher than the prevailing UHT
process.

16. Comparison of ISI with
conventional Heat treatments
Technology Time(s) Temperature
(°C)
Denaturati
on of whey
proteins
(%)
Log reduction B.
stearothermophilus
spores
Pasteurizatio
n
15-1 72-80 4-8 0
Indirect UHT 20-5 130-145 75-90 6
Direct UHT 6-2 142-150 60-85 6
ISI 0.1 160-180 25 6
Tamime (2009)

17. Heat treatments for specific
dairy products
72–120°C 15
sec to 30min
Heating
before
concentratio
n
Reduction of
microbial
load, inactivate
enzymes
Stabilizing the proteins
or controlled
denaturation of
proteins
70–95°C
(outlet) and
180–230°C
(inlet) Few
seconds
Heating of
milk
concentrate
in a spray
dryer
Reduced water
activity, reduced
chances of
microbial
survival
Drying, Product can be
stored at room
temperature for more
than a year

18. Scalding at
40°C
Scalding of
cheese curd
Felicitates
growth of
starters
Sufficient to expel whey
Whey separation, final
product moisture
control and cheese
body
80°C 30 min or
90°C for 10
min
Heat
treatment of
milk for
yoghurt
Reduction of
bacteriophages,
microbes etc.
Improve viscosity and
texture of yoghurt in
addition to reduction
in
microbial load

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