Interactions of Food Proteins - ACS Publications - American Chemical

Chapter 5

Milk Protein Ingredients Their Role in Food Systems

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Steve J. Haylock and Wayne B. Sanderson New Zealand Dairy Research Institute, Private Bag, Palmerston North, New Zealand

The roles which milk protein ingredients play in food systems are diverse. In multi-component food products, interactions occur between ingredients. The characteristics of these food products depend considerably on interactions. Predicting changes in the characteristics of food products from the physico-chemical properties of ingredients is difficult at present. The results of interactions between ingredients can be evaluated by measuring the changes in food product characteristics, caused by changes in the levels of ingredients. Examples showing the application of milk protein ingredients in a water-added ham and a yellow layer cake are discussed. In both cases desirable product characteristics have been optimized through the interaction of milk protein ingredients with other components in the food system. Milk protein ingredients are used by many sectors of the food industry (1-3). These ingredients are produced with a number of different properties and they are used i n food systems for a wide range of purposes. Studies on the functional properties of isolated milk protein products continue to be carried cut and the results from these illustrate the versatility of milk proteins in the range of physicochemical or functional properties which they are able to demonstrate (4=5). Rather less information though, has appeared in the literature on the roles which milk proteins assume in food systems. Some of the reasons for this are the confidential nature of many food formulations but equally responsible i s the complex nature of many of todays formulated foods and the difficulty i n interpreting the functional contribution of individual ingredients.

0097-6156/91/0454-Ό059$06.00/0 © 1991 American Chemical Society In Interactions of Food Proteins; Parris, N., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.

INTERACTIONS OF FOOD PROTEINS

60 Milk Proteins

There are two fundamentally different groups of proteins present i n milk, the casein proteins and the whey proteins. I t i s possible to distinguish between these two groups of proteins on the basis of the properties they exhibit. A number of these properties are shown i n Table I (3).


Table I.

Properties of milk proteins

Protein Type

Properties

Casein

Contains strongly hydrophobic regions Contains l i t t l e cysteine Random c o i l structure Heat stable Unstable in acidic conditions

Whey

Balance of hydrophilic and hydrophobic residues Contains cysteine and cystine Globular structure, much helical content Easily heat denatured Stable in mildly acidic conditions

Milk protein manufacturers use these different characteristics as the basis for isolating or separating different protein components from milk. Casein proteins are isolated from skimmed milk using precipitation. Ihis can be brought about by acidification of the milk to pH 4.6, or, by encouraging the hydrophobic interaction of casein molecules by removing the hydrophilic part of the molecule with the action of rennet enzyme. Whey proteins are far less sensitive to acidic pH conditions and consequently after removal of the casein proteins, these can be purified from the remaining carbohydrate and mineral material by filtration, ion exchange or heat-precipitation techniques. The protein products which are isolated from casein and whey consists of a number of individual proteins. Table II shows the major proteins in each group and their percentage contribution to the total protein i n milk (3). Ihe isolation of individual casein and whey proteins i s possible in the laboratory and i n some instances i n the pilot plant and manufacturing plant (6-7). A potentially rewarding area of research w i l l be the isolation of usable quantities of individual proteins for evaluation of their functional properties and their performance i n food systems. Ingredient Manufacture and Usage The isolation and separation techniques used for casein and whey proteins form the basis of designing specific milk protein ingredients. The manufacturers of these ingredients though, use a number of other techniques along with these isolation procedures i n creating dairy ingredients with the required properties. Some of the more important techniques used by manufacturers to modify the properties of the milk proteins are shown in Table III (8). In Interactions of Food Proteins; Parris, N., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.

5.

HAYLOCK AND SANDERSON

Table II. Protein Type

Casein


Whey

Milk Protein Ingredients

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Major protein components i n milk Individual Proteins

Total Milk Protein (%)

a casein β casein Κ casein casein β lactoglobulin α lactalbumin Proteose peptone Immunoglobulins Bovine Serum Albumin

45-55 23-35 8-15 3-7 7-12 2-5 2-6 2-3 ca 1

s

Much of the information detailing how these techniques are able to affect the properties of milk protein ingredients i s proprietary to ingredient manufacturers. Some information has been published though, on p^/temperature/time treatments and the adjustment of mineral balance (9-12). One or a number of these techniques may be selected in order to enhance the properties of the ingredients required. The reasons why dairy ingredients based on milk proteins are used so extensively by food manufacturers l i e with the varied range of functional properties which they exhibit, their excellent nutritional quality and their overall ability to contribute beneficially to formulated food systems. Much has been written about the functional properties exhibited by milk proteins and a number of these which have been discussed in the literature are listed in Table IV (4.5.13-15). Many of the functional properties which have been discussed i n the scientific literature relate to properties exhibited by those proteins i n simple solutions rather than in complex, multi-component systems which are typical of todays formulated foods. There i s no doubt that dairy proteins are extremely useful ingredients to the food manufacturer. There i s also no doubt that these proteins exhibit a broad range of functional properties in simple systems. What i s not clear however, i s the relationship between these simple functional properties and the role of proteins, as ingredients, in complex food systems. Experiences in our laboratories confirm findings in the literature which show that as soon as other components are added to proteins in simple test situations then the original functional properties of the protein become considerably modified (16). This creates a problem for the dairy ingredient chemist i n not being able to relate functional properties to a required response i n a food system. However, on the other hand the fact that other ingredients in food systems are capable of modifying the functional properties of milk proteins means that there i s an additional challenge to food technologists. That i s , to understand which significant interactions w i l l occur between ingredients and how to exploit these to bring about desirable properties in food systems.

In Interactions of Food Proteins; Parris, N., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.


62 Table III.

Protein Modification Techniques Used i n Ingredient Manufacture

Adjustment of mineral balance (cations and anions) Hydrolysis Temperature/time treatments pH/time treatments


Selection of protein concentration Use of complementary ingredients

Table IV.

Functional Properties Exhibited by Milk Proteins

Functional Property

Protein Type

Foam formation and stability Emulsification and fat binding Gelation Heat stability Water binding Viscosity and texture modification Solubility - neutral pH - acidic pH Solution opacity

Casein and Whey Casein and Whey Whey Casein Casein and Whey Casein Whey and casein Whey Casein

Food Systems Using Milk Protein Ingredients Although there i s difficulty in determining the relationship between simple solution functionality and complex food system functionality, nevertheless many different protein products are used in a wide range of foods. Table V shows a number of the more significant food applications where milk protein ingredients are used (17-23). It i s likely that in a l l the food products shown i n Table V, interactions w i l l occur between the milk proteins and other components i n the formulation, particularly where the milk protein i s used for a functional purpose as compared to a nutritional purpose. Given the nature of the molecular structures of the milk proteins i t i s possible to envisage a number of different mechanisms for interactions between milk proteins and other food ingredients. These include hydrophobic interactions, hydrophilic interactions, salt bridges, hydrogen bonding and sulphydryl reactions (15).


5. HAYLOCK AND SANDERSON


Table V.


Food Products Utilizing Milk Protein Ingredients

Category

Product Type

Protein Used

Analogue dairy products

Whipped topping Coffee whitener Imitation cheese Margarine Low fat spreads

Casein Casein Casein Casein Casein

Bakery

Egg replacers - cakes & pastry

Whey

Beverages

Acidic beverages

Whey

Confectionery

Marshmallow Caramel

Casein Casein, Whey

Meat

Sausage products Ham products Fish products Poultry products

Casein Whey Whey, Casein Casein, Whey

Nutritional products

Diet formula Infant formula

Casein, Whey Whey, Casein

Dairy products

Processed cheese Yoghurt

Casein Casein, Whey

Interactions i n Food Systems Formulated foods can contain a wide variety of ingredients: fats, proteins, salts, stabilizers, emulsifiers, acidulants, simple sugars etc. In assessing the likelihood of potential interactions i t must be assumed that i f an ingredient i s present then i t i s likely to be able to interact with the other ingredients in the food formulation (6). Making predictions then, about the properties of a food system on the basis of interactions which are likely to occur i s a d i f f i c u l t way to determine the value of ingredients to a particular system. The results of interactions with protein ingredients i n food systems, though, can be measured. This can be done by measuring the response of particular food system parameters to changes i n the concentration of the protein ingredients. Two food systems which have been studied in this way are the water-added ham and the yellow layer cake. Ham Products. These products are popular i n many parts of the world. They range from traditional dry cured bone in ham products, through to products where the raw meat can form only 50% of the finished article. Intermediate within this range are a number of cured pork products where the pork meat i s only 60-75% of the cooked product.


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At lower extension levels the extraction of myofibrillar meat proteins using salt and phosphate i s generally sufficient to provide the gelling and waterbinding properties required i n ham products. Higher levels of extension though are often the norm i n many countries and as a consequence of this, a range of food ingredients are permitted i n these products. Both caseinate and whey protein ingredients are used i n these systems for their waterbinding and gelling properties. These ingredients are able to interact with and complement the soluble myofibrillar meat proteins. A series of water-added ham products were prepared i n order to optimize the ratio of two milk protein ingredients, Whey Protein Concentrate (WPC(x)) and Total Milk Proteinate (TMP(y) ). A formulation which gave a 60% extension of the original pork meat was used. The steps involved i n the manufacturing process for these hams are shown i n Table VT. Food products can never be characterized by a single property and water-added hams are no exception to this. There w i l l always be a balance between a number of properties which w i l l combine together to make an acceptable product. The factors which are considered to be of major importance i n a water-added ham product are shown i n Table VII along with the relative weighting of these factors. The concentration of WPC(x) was varied between 1.0% and 2.5% while the concentration of TMP(y) was varied between 0.5% and 1.5%. So that the concentration of the raw meat and brine was not varied, lactose was used to balance the formulation. The combined addition level for WPC(x), TMP(y) and lactose was 3.5%.

Table VT.

Manufacturing Process for Water-Added Ham Products

Raw Meat Preparation

Milk Protein Hydration

(fat tximming, tenderising grinding)

(water, WPC(x), TMP(y)

Brine Pn^Hration

(water, ice, salt, dextrose, sodium tripolyphosphate, sodium hexametaphosphate, sodium erythrobate, sodium nitrite)

Tumbling under Vacuum Forming Into Impermeable Casings Cooking or Smoking


5.

HAYLOCK AND SANDERSON Table VII.

Product Characteristics for Water-Added Ham Products

Product Characteristics

Percentage Weighting

Cooked yield

35

Syneresis

20

Texture - Breakstrength - Rigidity - Elasticity Downloaded by UNIV OF GUELPH LIBRARY on July 1, 2012 | http://pubs.acs.org Publication Date: February 19, 1991 | doi: 10.1021/bk-1991-0454.ch005


15 12.5 17.5

Cooked yield was determined by dividing the weight of the cooked ham by the weight of the raw ham. Syneresis was determined by measuring the moisture loss after storage of sliced product for 14 days i n vacuum packs. Texture measurements were carried out using an Instron Universal testing machine. The break-strength was defined as the pressure required to break a 60 mm slice of ham. The rigidity was defined as the pressure required to deform the ham by 8 mm. Ihe elasticity was defined as the distance the ham was compressed prior to breakage, divided by the thickness of the slice. Figures l ( a - c) and 2(a and b) show response surface diagrams of the product properties which were measured and how these were affected by the changing levels of the two protein ingredients. I t i s apparent from these figures that the optimization of a formulation for a certain product property w i l l often be to the detriment of other properties. Under these circumstances a cxjmpromise must be reached. The relative importance or the weighting assigned to the different product properties may be varied depending on the product required. Hie weighting factors are generally assigned subjectively by an experienced worker i n the area. Figure 2c shows a further response surface diagram. In this case the ζ axis i s the compromise metric which takes into account each of the measured properties. Ihe best compromise formulation with regard to the levels of WPC(x) and IMP(y) i s when ζ i s at a ininimum value. Egg Replacer. Whole eggs are regarded as multi-functional ingredients i n a number of food systems i n which they are used (24). This i s because they consist of a complex mixture of proteins, lipids and phospholipids (25). I t i s not surprising that ingredient manufacturers who have attempted to imitate the functionability of egg products, by supplying single component products as egg substitutes have met with, at best, moderate success to date. While the development of a universal egg substitute i s perhaps seme way off, i t i s possible to imitate the functionality of egg, to a substantial degree, in some specific food applications.


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(a)

Figure 1. Response surface diagrams for water-added ham products, (a) Cooked yield, (b) Syneresis, (c) Break-strength.




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(a)

WPC (x)

Figure 2. Response surface diagrams for water-added ham products, (a) Rigidity, (b) Elasticity, (c) Coi^rcmise metric.




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In a yellow layer cake or madeira cake, the major functional contributions to the product from the whole egg could be considered to be foam stability, emulsification and gelation (26). Whey protein concentrates, however, are also able to demonstrate these functional properties (27). There are a number of broad similarities between egg proteins and whey protein concentrates. The greatest similarities between these two groups of proteins are i n their globular structure, their ability to undergo heat denaturation and their significant content of sulphur containing amino acids. A series of yellow layer cakes were prepared to evaluate the performance of whey protein concentrate as an egg replacer by i t s e l f and i n combination with other interactive ingredients. Ihe formulation used for the control cake formulation containing whole egg i s shown in Table VIII. Whey protein concentrates were evaluated by replacing the dried whole-egg power with WPC on a protein basis. Cakes were assessed on the basis of crust characteristics, specific volume and compressibility. Measurement of crust colour was carried out using a Hunterlab Colour Quest. The a scale (red-green) was found to be most appropriate for measuring the extent of crust browning. Subjective assessments were made on other characteristics of the cake crust. Ihe specific volume was measured by rape seed displacement and the compressibility by a penetration test. Table IX shows the performance of these cakes in terms of their product properties. 1

Table VIII.

Ingredient Butter shortening Castor sugar Salt High ratio cake flour Baking powder Pregelatinized starch Dried whole-egg powder Colouring Flavouring Emulsifier Water

Formulation of Yellow Layer Cake Containing Whole Egg

Percentage 13.0 28.0 0.2 25.8 1-2 0.5 3.6 0.125 0.175 1-0 26.4



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Table IX. Performance of Cakes Using Egg and Whey Protein Concentrate

Protein Type Whole Egg

Property


Crust-colour -characteristics Specific volume (cm/g) Compressibility (mm)

SM = smooth NS - non-sticky

18 Ρ, S, SH 3.18 3.8

8 SM, NS, Μ 3.36 4.7

M = matt Ρ = pitted

WPC

S = sticky SH = shiney

The WPC-containing cake in comparison to the whole egg containing cake was characterized by a red-brown sticky crust, a slightly lower specific volume and a lower compressibility. Ihe WPCcontaining cake was not acceptable on the basis of the crust characteristics and the texture (compressibility). Cakes prepared with a range of additional interactive ingredients and WPC were able to highlight some of the areas where the WPC was functionally deficient. After careful selection of ingredients a series of optimization t r i a l s were carried out and the performance of the best WPC-containing cake i s shown i n Table X. Table X.

Performance of Cakes Using Additional Ingredients and WPC

Property

Whole Egg

WPC

Additional ingredients and WPC

Crust-colour -characteristics Specific volume (cm/g) Compressibility (mm)

8 SM, NS, M 3.36 4.7

18 P, S, SH 3.18 3.8

10.5 SM, NS, M 2.79 5.6

Here i t i s apparent that the cake formulation with the added ingredients has brought about a substantial improvement to the crust characteristics. The specific volume though, has been reduced to an unacceptable level with significant collapse on cooling and the texture of the cake has become crumbly as indicated by the compressibility data. A further series of ingredients were investigated for their ability to interact i n the cake system and overcome the low specific volume and the high compressibility. The performance of these cakes i s shown i n Table XI.



70 Table XI.

Performance of Cakes with Best WPC-GDntaining Formulation

Property


Crust-colour -characteristic's Specific volume (cm/g) Compressibility (mm)

Whole Egg Formulation

Best WPC-Containing Formulation

8 SM, NS, M 3.36 4.7

10.5 SM, NS, M 2.96 4.8

Ihe cake resulting from the best WPC-œnteining formulation i s acceptable albeit that the specific volume i s a l i t t l e lower than optimum. These results show that i t i s possible to replace whole egg in a yellow layer cake or madeira cake with a WPC-based ingredient, and produce an acceptable product. This has been achieved only through the optimization of interactions in the cake system. In this case an iterative procedure was required. Here the i n i t i a l formulation optimization did not produce a l l the required product properties and the optimization process needed to be repeated to arrive at the acceptable formulation. Conclusions These two examples of the application of milk protein ingredients i n food systems illustrate why these products are used and perhaps give an indication of the mechanisms which control their usage. In both cases the functionality exhibited by the dairy protein i n the food system i n question has been modified by other ingredients present i n the food product. It i s accepted that the functional properties exhibited by proteins i n simple systems do not always translate well to their use in formulated food systems. The most immediate challenge to the scientists and technologists working in this area i s to narrow the gap between the fundamental science of functional property elucidation and the technology of protein application into food systems. From the technologists point of view i t i s important that the roles which ingredients play in food systems are more clearly understood. From the fundamental scientist's point of view i t i s important that functional property evaluations are extended beyond simple systems to include other typical food ingredients so that the extent of ingredient interactions can be quantified. In conclusion then, the roles of milk proteins in food systems are many and varied. Their wide use within the food industry has stemmed from both the range of functional properties which they exhibit and also their continued success in promoting desirable properties in formulated food systems. Much s t i l l remains to be learnt though, i n attempting to bring about the convergence of these two areas of milk protein research.




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Actocwledgments The original research work referred to in this paper was carried out within the Food Ingredients Section at the New Zealand Dairy Research Institute. The authors would like to thank Miss Sue Croft, Ms Melanie Gordon, Mr Rowland Cocup and Mr Tony Fayerman for supplying original material for publication. The authors would also like to thank Dr Lance Broad for his contribution in carrying out statistical analyses.


Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

Sanderson, W. B. Bulletin of the International Dairy Federation. 1988, No. 224 33-35. Southward, C. R.; Walker, N. J. In CRC Handbook of Processing and Utilization in Agriculture; Wolff, I. A. Ed.; CRC Press, Boca Raton, Fla. 1982; Vol. 1, p 445. Evans, E. W. In Advances in Food Research; Academic Press Inc., 1987; 31, Chapter 4. Mulvihill, D. M.; Fox, P. F. Bulletin of the International Dairy Federation; 1987; No. 209, 3-11. Leman, J . ; Kinsella, J. E. Critical reviews in food science and nutrition; 1989; 28 (2) 115-138. Marshall, K. R.; Harper, W. J. Bulletin of the International Dairy Federation 1988, No. 233, p 21-32. Modler, W. H.; Jones, J. D. Food Technology 1987, 41, 10 p 114. Kirkpatrick, K. J . ; Fenwick, R. M. Food Technology 1987, 41, 10 p 58. Towler, C. New Zealand Journal of Dairy Science and Technology 1976, 11, 24. Roeper, J. New Zealand Journal of Dairy Science and Technology 1977, 12, 182. Connolly, P. B. U.S. Patent 4 376 072, 1982. Ottenhof, H. A. W. Ε. M. U.S. Patent 4 519 945, 1985. Kinsella, J. E. Critical reviews in Food Science and Nutrition 1976 p 219. Morr, C. V. in Developments in Dairy Chemistry; Fox, P. Ed.; Applied Science Publishers, London, 1982; Chapter 12. Schut J. The Role of Milk Proteins Added to Foods; The Dutch Dairy Bureau: Cort van Lindenstraat 7, 2288 Ε V Rijswijk, The Netherlands, 1980. Harper, W. J . ; Peltonen, R.; Hayes, J. Food Prod. Dev., 1980, 14, 10 p 52-56. Anon. Bulletin of the International Dairy Federation, 1989 No. 239. Cocup, R. O.; Sanderson, W. B. Food Technology, 1987 41, 10 p 86. Harper, W. J. Proc. APV Symposium for the Soft Drink Fruit Juice; Dairy and Food Industry, Auckland, New Zealand, p 40. Lim, D. M. Leatherhead Food R.A. Scientific and Technical Survey, No. 120, 1980.


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21. van den Hoven, M. Food Technology, 1987, 41, 10 p 72. 22. McDermott, R. L. Food Technology, 1987, 41, 10 p 91. 23. Kjaergaard, Jensen, G.; Ipsen, R. H.; Ilsøe, C. Food Technology, 1987, 41, 10 p 66. 24. Baldwin, R. W. In Egg Science and Technology; AVI Publishing Co. Inc., Connecticut, 1977, Chapter 16. 25. Powrie, W. D. In Egg Science and Technology; AVI Publishing Co. Inc., Connecticut, 1977, Chapter 6. 26. Shepherd, I. S.; Yoell R. W. In Food Emulsions; Ed.; S. Friberg; Marcel Dekker Inc., New York, Basel, 1976, Chapter 5. 27. De Wit, J. N. Neth. Milk Dairy J. 1984, 38. RECEIVED

August 14, 1990


Interactions of Food Proteins - ACS Publications - American Chemical

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