The pasteurization of liquid whole egg

115 Pages·012.215 MB·English

by  Greco, Philip Anthony

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'S»; PAS TEUR IZATION W LIQUID 1B0UE Wm
by
Pill lip Anthony Sr#b©
A fbssis Submitted to the Graduate Faculty
for the Degree of
DOCTOR m PHILOSOPHY
Major Subjects: Poultry Products
Sanitary and food Bacteriology
Approved:
Iowa State College
1945
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UMI Number: DP11900
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T A G i S , E 4 u
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m BLS OF CONPEMTS
Fags
IRTRODUC TIOH . . ........................... : , 1
REVIEWO P LITERATURE .... ... * * * » . . , * ........* 8
Sources of Microorganisms la Liquid whole Egg . * . . . . 8
General . . 8
The Shell Sgg . . . . . . . . . . . . . . . . . . . . * 9
Possible modes of penetration 10
Before laying . . . * . . . * * .. . . . . . * 10
After laying * -* * . . . . . ................. 14
Factors affecting the growth of
microorganlsma within the shell egg. . . . . . . . 18
Mucilaginous coating.......................18
Shell and shell membranes .* * * . « * . . . » 19
Bacteriostatic properties ................... 19
Las chts chenko * s factor . . . . . . . . . . . 20
Lysozyrae............................... 21
pH . . . . . . . . . . . . . . . . . . . . . . 22
Indigestibility of native proteins
and viscosity . . . . .♦ . . . . . . . . . . . 23
Per cent of eggs infected . . . 24
Fresh eggs 24
Stored eggs . . * 27
Types of mleroorgan!sms found in eggs . ......... 29
From The Breaker . . . . . . . . . . . . . . . . . . . 81
' From The Utensils 31
The Effect of Heat on Liquid Whole Egg . ... . . . . * . » 32
Efficacy of pasteurization on Foods . . . . . . . . . . . . 34
Theoretical Aspects ....... . ......... . . . . . 35
Practical Applications . . . . . . . . . ......... * 38
lllk 39
Bactericidal efficiency................... 40'
Oream for butter-making . . . . . . . . . . . . . . 41
Apple juice 42
f*
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Hi
previous Attempts to Reduce the
Bacterial Content In Eggs . . . . *. * . , 42
The Shell Egg ♦ 43
The Liquid Whole Egg 43
Summary of Historical . . . . . . . . . . . . . . . . . 45
mwmma-fi.il* * . . . . . . ............ 47
Methods . . . . * *, 47
General * ». « * . * ,*...........* * * * * *■ » , . 47
Sources of eggs * , . . . 47
Heating technique . . *.■*«**»•**,* , . , , 47
Bacteriological * ........... * . * * 49
Shell egg , , , . . . . . . . . . . . . . 49
Liquid whole egg . . . * . . . . . . . . . . . . 51
Bacterial cultures . . . . , « . . . . . . . . * S3
Culture media ............................ 54
Viscosity . * . . . . . . . . . . . . . . . . . . . .
Results and Discussion .» * . * . • * . . . . . * . . . 5®
Bacterial Content of shell Eggs . • * . . . . . . ♦ 56
Heat Denaturatlon of Liquid Whole Egg . . . . . . . 57
Thermal Death Point Studies » • « * * . * . . . . . 65
Thermal Death Rate * * . . . . . * * . . . . . . . . 66
General ............ 66
Culture H-, in melange prepared
from fresh and aged eggs . . . . . . . . . . . . 77
Effect of pH . . . . . . . . . . . . . . . . . . 80
Effect of short growth period . . . . . . . . . . 82
Comparison of thermal death rates of
culture in raw milk and liquid whole egg . . . 84
Thermal Death Studies on a Mixture of Microorganisms 87
Commercial Trial ... * * . . . . . . . . . * * . . 90
Microorganisms Isolated from Commercially
Prepare d Melange During Pasteurization # . . . . * . 94
CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . * 96
SUMMART . . . . . . . . . . . * . 97
LITERATURE C l ® . . . . . . . . . * . . . . . . . . . . . 99
m m r n m x m & m . . . . . . . . . * * . . . . . . . * . . 109
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- I -
INTRODUCTION
History records the effort* of man to discover and. Invent
method# for preserving food. Various procedures have been
used* the freezing of fish, the burying of potatoes and other
vegetable## the drying of fruits, meat# and vegetable# by the
son, and the smoking, and pickling of food#.- lore recently
the um of high temperatures ha#, bee*# an .additional method*
©a# egg has been subjected to all these fossa* of preser­
vation. Perhaps on# of the earliest method# was that of the
Chinese* The product was and still Is called “Pldan®, The
shell-egg# mmm placed in a mixture of salt and ashes and
stored for a period of time, usually *i* months, after which
the egg# were consumed, fanner (1932) has presented a more
detailed discussion of this product.
low temperatures have been frequently used 'in the
preservation,of foods, fhe shell-egg must be stored at tern-
#•
peratures above it# freezing point because of the deleterious
effect# resulting from freezing the contents of the egg in
the shell. Cold storage, 'however, has been found, to retard
the .spoilage in eggs,- but not to- prevent it. It has been
found by various workers that growth of some microorganism#
occurs even at t»peratures as low as 0°C. m inert gas,-
such as carbon dioxide, when added to- the atmosphere of the
storage chamber in order to create anaerobic or reduced oxygen
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conditions, inhibits the growth of aerobic organisms, whisht
'haw been reported to b© the worst offenders. The us# of
carbon dioxide also lowers the pH of the egg which helps to
maintain the physical and organoleptic qualities of the shell-
egg. This procedure Is utilised on the European continent
under the trade name of H;Lescard©”.
She limitations of storing eggs., in the shell pared the
way for the development of a new method of preserving them*
This new procedure was the breaking out of the contents of
the shell-egg -and freezing It as whole egg, yolk or albumen.
The frozen egg- industry started .about thirty years ago as an
offshoot of the shell-egg Industry* It was found that "leakers8,.
•dirties** ”cracks”, ©to. could be broken out and preserved
better in the frozen state than m sheli-egg#. Prom this small
beginning the industry has grown both la the quality of Its
«
product and in the amount of its production. Today freezing
■eggs is recognized as a very efficient .and profitable means
of preserving eggs. fig. 1 show# the yearly production of
frozen eggs for the past 20 years.*
The bakers, noodle .and aayosetais.® manufacturers., etc*,
have found that the frozen product Is of uniform and good
quality throughout the year {most of the eggs are broken and
frozen In the spring when the quality is good) 'and teat it le­
tters suitable for their purpose# than are shell-eggs. Then,
too, tee price of shell-eggs Is low In tee spring 'When most
of tee frozen egg# are produced.
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Some other reasons for the growth of the Industry are the
continual »el«etioa of better eggs for breaking, better sani­
tation of the plant and the worker, better methods of freezing,
transportation, merchandizing, and, of course, lower cost.
These factors all contributed -in producing a frozen egg product
upon which the tasker -end other mm®, can rely,
Radabaugh (1989) presented a brief resume of the %tnah~
room'* growth of this- industry. He stated that the cost -of
handling- and storing one dozen sheil-egg# (for the average
storage period) is slightly lower than the cost of producing
and storing an equivalent amount of frozen eggs-. However,- the
labor costs saved by -manufacturers using large quantities -of
frozen egg#, the fact that the prices of frozen eggs remain
sore nearly constant throughout the year,, the uniformity of
the product and toe lower transportation cost# more than off­
set tois difference in cost.
During toe infancy of toe tofejstry, toe bacteriological
qualities and wholesomeneas of frozen eggs were far- from satis­
factory. Because of toes© fact# toe United State# Dep&rtmert
of Agriculture undertook to study toe factors responsible for
th® questionable quality in this food- prefect* Stiles and
Bate# {1912) examined Sit .sample# of' commercially frozen eggs,
of which they found only 20 per cent contained less toam
1,000,000 microorganisms per gram. On toe other hand, they
found that frozen eggs prepared in their- laboratory from
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