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PROMOTI:ON OF BROWNING
m
TEE DEVELC>BU!NT OF NEW DAIRY HWDUC!.ISA niesi.s Presented to
the Faoul ty of the Department of Food Science and Biotechnology Massey University
In Partial Ful.:f'ilment
of the Requirements for the Degree Jlaster of Food Technology in Food Processing
by
Wa.rwi.ok David Ward July 1967
"It is not enough to know; -we must turn 'tlhat we know to account. It is not enough to mil; we must do.11
- Goethe
ACKNOWLEDGEKENTS
'.I.he author wishes to thank the supervising camni ttee o£ Mr. H. A. L. Morris (Convenor), Dr. E. L. Richard.a, and Dr. R. M:. Dolby. Sincere appreciation and grati tud.e go to Mr. H. A. L. Morris for his encouragement, and particularly for his keen interest in this study. His practical experience, willingness to talce part in lengthy discussions, and help in the planning and presentation of this thesis has proved to be invaluable.
'.Ihanks are due to the Dairy Prod.uc ti on and Marketing Board and the San- itarium Health Food Canpany for financial assistance.
Special thanks to Miss D. Scott for the excellent photography and printing of the graphs and photographs, and also to Miss
c.
Ki tohell f'or her hand in the photographs, studio work, and fixing of the graphs and photographs.For much frui tt'ul help and discussion, the author is indebted to the willingness o£ Mr. J. G. Clarke, Dr. W. B. Sanderson, and Kr. D. Box, of the New l.ealand Dairy Research Institute.
To the l.mtiring help and patience ofhis sister, Miss :M. Ward, in the prep- aration and typing of this thesis the author is gratefully indebted for the final presentati.cn. 'lhe author also wishes to thank his family and close friends for their encouragement, and for their help in so many ways to make this work an enjoyable experience.
nie assistance and interest of numerous other people "tilo have contributed in many eya is also muoh appreciated and baa made the "WOrk on this thesis that muoh more interesting.
TABLE OF CONTEN'IS
PART A. BASIC SWDIES ON 'IHE BROWNING OF MIIK SOIIDS
SECTION I. A REVIEW OF PREVIOUS RESEARCH INTO 'IHE BROWNING OF
DAIRY PRODOO'IS
•
• •• • • •
• • • ••
• • I. Introduoti on• •
•• • •
•• •
• • • • • II. Reao tan ts and Jleohani sm•
•• •
•• .. • • •
III. :Ehencmena Associated with Browning•
• ••
• •• •
A. Ccmpound fomation
•
•• • • • • • •
•B.
Reducing substa.noes• •
• ••
•• • • • •
o.
Strecker degradation• • • •
•• • • • • •
D. loss of nutritive value• •
• • • ••
• • •E.
!Dss of protein solubility •• • • • • • • •
IV. Caramelized Flavour • !• • •
•• •
• •• •
•v.
Factors Atteoting the Bate of the Browning Reao ti on• •
VI. Salient Features of Previous Work
• • • • •
•• •
SECTION II. DEVEIDBrnNT OF A KEMOD FOR MEASURING '1HE DEGREE OF
BROWNING IN A DAIRY PRODUCT SISTml • • • • • • • •
I.
Chemical Jlethods •• • • •
•• • • • • • • •
A. Literature review• • •
•• • •
•• • • •
B. Selection of a method for studies
an
adva:noed browning in sweetened condensed milk• •
•• • • • •
n.
Development of a Method. of Measuring Product Colour as an Index to the Progress and Rate of the Browning Reaction •PAGE
1 2
3 8
910 10 11 11 13 15 17
19
20 20
24
28
PAGE A. Li. tera ture review •
• •
• • • • ••
• •B.
Development of a method tor the measurement ofbrowning - based
an
product colour ••
••
••
o.
A new method of plotting reflectance results tod.etel11line the rate of' browning • • • • • • • III. Correlation Between Chemical (HMF) and :Ehysical (Reflectance)
.Methods for the lleasurement of the Rate of Browning •
•
IV. Summary
•
•• • •
• • • ••
• • • • •. . .
SECTIOO" III. A BASIC STUDY OF FACTOBS INFUJENCDlg. BROWNING
m
SWEETENEDI.
II.
III.
CONDENSED MILK • • •
•
• ••
• • • ••
• • Studies on the Effect of Temperature on the Developmentof Dairy Caramel • • • • • • • • • • • • Study of the Effect of Moisture Concentration on the Rate
of' Browning of Sweetened Condensed Milk • • • • • •
A.
Effect of moisture concentration on browning insweetened condensed milk
•
• • • • • • • •B.
Effect of moisture content on broming in a modelsystem oonta1 ning skim milk pawder • • • • • •
c.
A proposed theory to explain the effect of moisture oonoentratiai on browning in liquid systems - arisingout of the previous study of sweetene~ condensed milk and glycerol-milk powder systems
• •
• • ••
D. Changes in moisture concentration during browning of sweetened condensed milk
• •
• • • •• •
• Studies an the Ef:feot of pH on Browning in SweetenedCondensed lti.lk • • • • • • • • •
•
•• • • 28
29
32
36 39
41
1+3
49
49
51
55
58
61
PAGE
IV. Canparisan of the E:fteot of Two Sugars on the Brcnming
Reaction in Concentrated llilk •
•
• • • ••
•66 A.
Effect on the rate of browning•
• •• •
•• 69
B.
Rate of solubility decrease • ••
•• • • • 69
v.
Summary of Factors Influencing Browning in SweetenedCondensed Milk •
• • • • •
•• •
•• • •
• 70PART B. DEVEU>PlmlT OF NEf PRODUCTS BY PROMOTING BROWNING
m
MIIK SOLIDSSECTICN IV. S'IDDIES ON 'lHE DEVEIDFMENT OF A SWEETENED CARAMELIZED DAIRY
SffiEAD
•
•• • • • • •
••
• • •• • • 74
I. In trod.uo ti on • • • • •
•
•• •
• • • 75 II. Flavour Development• •
• ••
•• •
•• • •
•76
A. '.Iheory• • •
••
••
••
•• • • •
•• 76 B.
Teohnologioal applications•
•• •
••
•• 78
III. Texture Development
•
••
• •• • •
• • •83
A. '.Iheoretioal study
•
••
• ••
• •• • •
•83 B.
Teohnologl.oal applioati.ons• • • •
•• ' • •
100IV. Possible Camneroial Production Methods • • • • •
•
102 A. Caramelization in the packaging container• •
••
102B•
Carameliza ticm
before packaging• • • • •
••
107c.
Possible oamneroial product types• • • • • • •
111v.
Studies en the Changes O:Jourring During Storage otCaramelized Sweetened Ccmdensed Mille.
•
~ ~ •• •
• 112VI.
Summary.• • • • • •
•• •
•• • - · • • • •
122SECTION V. STUDIES W mE DEVELOPMENT OF A POROUS WAFER FROll
I.
II.
III.
IV.
MIIK SOLIDS Introduction
•
• • • • • • • • • • • • • •
• •
•• • • •
~eoretical Background Discussion A. Bubble mechanics • • • • B. Foam preparati
an • • • •
•
•
•
•
• • •
•• •
• • • •
••
• • • •
••
• • • •
• • Studiesan
Methods of, and Factors Affecting Aerationot
lfilk Solids Solutions • • • • • • • • • A. Methods of aeration • • • • • • • •
1. Whipping and/or injection o£ gas (air)
2.
Cb.emical leavening• •
•• • 3.
~ennal liberation of moisture vapour4.
Vacuum expansion •B. Factors a.f'fecting aeration
•
•
•
•
• •
• •
•
•
•
• •
•
•
•
•
•
•
•
•
• •
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•
•
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•
•
•
•
•
•
• 1 • Introduction and literature review •
• • • 2.
Experimental ~tudies3.
Conclusions • • • Method of Drying to a Solid FoamA. Oven or hot air drying • B. Vacuum foam drying •
•
•
•
•
•
• •
••
••
• •
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• •• • •
• ' ' •
•' • • • •
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• • • • •
PAGE
• 125
• 126
• 127
• 127
• 131
• 132
• 132
• 132
• 132
• 135
• 135
• 137
• 137
• 141
• 159
• 161
• 161
• 167
v.
Possible Camneroial Aspeots of this Wafer Typeot
Product • 176 A.Texture • • • • • • • • • • •
! • ! • • 1 76 B. Flavour• • • • • •
•o.
Use of f'ull cream milk solids D. Packaging and storage • • •• •
• •
•
•
• • •
•
• •
•• •
•
•
' 177
. 1n
• 178 TI • Stumnal'y • • • • • • • • • • • • • • • • • • 180
PAGE SECTION VI. S1UDIES ON 'lHE DEVEWBIENT OF A CONC:ElimATED CARAMEL
FLAVOUR BASE • • • • • • • • • • • • • • • 182 I. Introduction • • • • • • • • • • • • • 183
II. Liquid Concentrate • • • • • • • • • • • • • • 183
III. Powiered Caramel Flavour • • • • • • • • • • •
•
185SECTION VII. SUGGESTICNS FOR FURmER STUDY • • • • • • • • • • 190
• • • •
•
• • • • • • • • • • • • • • • • • 195BIBLIOGRAEHY
• • • • • • • • • • • ••
• • • • • • • 203One readily demonstratable effect resulting fran the prolonged heat treatment of milk is browning. A form of non-enzymic browning due to inter- action of aldoses with free amino-groups occurs in many foods, and hence this reaction is of broad significance in the food field; e.g., dry milk products (29), processed potatoes (95), dried fruit (-l 02), dried whole eggs ( 73), dried meat (99),
and. liquid and. concentrated milk products (33,83). fue significance of browning in food technology has
two
aspects - the desirable and the undesirable.In many areas of the world today people are undernourished, malnourished, and. even starved. At the same time in other parts of the world, food is abundant to the point of substantial excess. Although many factors contribute to this unbalance, food spoilage is an important considers.ti.en. Sane emess food oan be processed and. stored in a practical manner involving little or no deter- ioration, but sane of i t faces spoilage despite man's preventive efforts. One vexing problem of food spoilage is browning 'Whi~h may atteot many food. products.
1hese include dried food such as milk, eggs, f'rui ts, fruit juices, meat, fish and vegetables ( 12) ; canned milk, fruit, and vegetables; and. other foods such as molasses. Loss of palatability and nutri ti.ve value as well as undesirable ohanges in physical properties frequently attend the brOWling of f'ood. to va.ry.i.ng degrees of' intensity, depending an the stage to llhich the reaction has progressed.
~s is the undesirable aspeot of br01llling.
On the other hand, the Maillard reaction can make a positive cantributicn to food. technology by producing desirable colours, flavours and arcmas in ~
foods auoh as re~to-serve oereal.s, toffees, roasted coffee, malted barley, and baked goods (65). ibasting, bald.ng, roasting, and frying are processes
aimed at intentionally browning the f'ood.. Although there is acme loss of amino acids llhen these flavours are produced, the loss is not usually of much import- 8ll0e and is accepted as a price 1'0rth paying. 'lhe Maillard. reaction can be explai ted for particular purposes by the ad.di ti on of reduoing agents to the food. For example, the inclusion of milk powder in a loaf of bread peDrl. ts more even toasting at a lower temperature because of the presenoe of lactose.
Another example is the production of chiaken and meat-like flavours by heating amino acids w1. th pentose sugars and. aldehydes. 'lhe distinotive caramel and buttersootoh flavours derived frc:m dairy produots result from the bro"WDing of milk or milk cc:mponents. 'Illus, it is clear that bro..Ung has two aspects, both
of "filioh canoern the acceptability of man• s food.
It is the latter aspect
ooh
is of principal interest in the present work. By prc:moting browning in milk solids to varying degrees of intensity, a range of palatable caramel flavours may be obtained. It is clear that dairy- caramel flavours are appetizing by the fact that caramelized milk products are very popular, and are eaten extensively in South America, India, and Europe.Tradi ti anal products produced d.onestioally include 'Dulce de leohe' (Argentina, Uruguay), 1Manyar blanco' (Cbile), and 1Khoa1 (India). In Argentina, 2,800 tons of 'DuJ.oe de leohe' are camnercially produced per annum;
98%
of this produa:tian is consumed intenial iy. Clearly then, many people enjoy d.airy~aramel flavours"lilen purposely produced. With the realization that a potential market is already present, the purpose of this thesis is to explore the possibility of diversifying New Zeal.and. dairy produots by the prcmoted oaramelisatian of milk solids.
A review of previous research into the browning reaotiai in milk showed that muoh 'WOrk has been done and copious literature exists, but most of this neglects the beneficial effects of nai-enzymio browning in millt and oanoentrates
on the deteriorative effects. Consequently, methods of measuring bl'O'ming mainly involve measurements of the reactants and early intemediates as a basis for inhibiting the early stages of browning. As a result· of this bias in
previous research, the first task of this study was to develop a method of measuring pranoted browning ("caramelization") in milk. '.!he method finally chosen was the reflectance measurement of colour.
A reliable method of measuring pranoted browning made possible a study of the factors affecting pranoted browning, and caramel f'lavour development, in S11eetened condensed milk. fue study was restricted to br01ll'li.ng in "liquid"
systems as the factors affecting browning in "dry" milk powder have been well documented
(65,83 ).
In this context, there were t\'IO principal areas of interest with regard to browning and associated changes in milk systems. One is practical and conoerns the manipulation of prooess and produot variables suoh as tempera- ture, time, pH, and moisture content, to obtain a controlled amount of browning.'.!he other is f'und.amental and concerns me.king the knowledge of milk and its behaviour as canplete as possible.
Without incorporation into palatable food structures and textures any flavour is of little value as food. Henoe, the remainder of this thesis is an exploration of the possibilities ot incorporating dairy caramel flavours into conventional food textures, struotures, and types ?ihich are of proven palat- ability. A survey of present food tonns marketed,. and a consideration of recent trends in food marketing suggests that the following product types are of proven consumer acceptance and worthy ot further study and development.
1. Sweet caramelized spread for use in the same way as jams; i.e., spread, pie filling, cakes, etc.
2. Porous waf'er or bisoui t type of product - pe:rilapa for use as a high protein supplement in a form llh:i.ch the consumer is familiar with.
3.
Concentrated dairy caramel flavour in pawder or liquid concentrate foxm for general food flavouring.4. Oanfeotions - sweets, toffees, milk caramel, hokey-pokey, etc.
( fue production of caramel confections is '91811 documented and
was
not studied further.)With an aim of developing these general produot types a :f'undamental study 118.S
undertaken to define the factors affecting flavour, colour, and texture of browned milk solids.
