Making cheese guilt free indulgence

Making cheese a guilt free indulgence

5:11 AM, 16th February 2018
Making cheese a guilt free indulgence
Bubble collapse event resulting in the formation of a microjet and Cross-sectional image of a double emulsion droplet, consisting of a large oil droplet holding smaller internalised water droplets.

A mouthwatering low-fat cheese sandwich is the dream of every diet conscious individual. Researchers from the ARC Dairy Innovation Hub have made this dream of low-calorie cheese come true with their double emulsion process.

The ARC Dairy Innovation Hub, University of Melbourne, Australia researchers include Dr Thomas Leong, Research Fellow, School of Chemistry; Dr Gregory Martin, Senior Lecturer, Chief Investigator, Department of Chemical Engineering and Professor Muthupandian Ashokkumar, Chief Investigator, School of Chemistry.

Research insight.

The development of milk streams with functionalized properties is of high interest to the dairy industry to add significant value to existing processes and product lines. The ARC Dairy Innovation Hub’s “Functionalized Milk Streams” project aims to develop and apply the platform technologies of double emulsions, ultrasound, homogenization and microfiltration to bring improved yield, quality and consistency of products such as cream cheese, mozzarella and low-fat cheddar.

The project is developing an improved understanding of the interplay between dairy fats and proteins within novel dairy products.

Double emulsion process to reduce the calorie value of cheese.

Emulsions are very important food systems. Water and oil do not readily mix together. An emulsion is a stabilized mixture of oil droplets in water (or water droplets in oil), whereby small droplets of one liquid phase are dispersed and stabilized in the other liquid phase. This stability is provided by an amphiphilic chemical species, known as an emulsifying agent. An emulsifier positions itself at the interface of oil and water, and by doing so limits the ability of the droplets to combine with neighbouring droplets, therefore preventing separation of the phases. Examples of natural emulsifiers widely present in food systems include proteins and fatty acids.

Some everyday examples of emulsions are milk and mayonnaise, which have oil droplets stabilized within an outer water phase, and butter which is an emulsion of water droplets stabilized within a fat structure.

Double emulsions are essentially an emulsion, that is dispersed within another emulsion. The type of double emulsion we are interested in is what we term water-in-oil-in-water type emulsions, which consist of water droplets that are emulsified within an oil phase, which in turn are emulsified into a surrounding water medium. The result is an emulsion of fat droplets that contain within them, an emulsion of tiny water droplets.

These types of emulsions offer great potential for producing tastier low-fat dairy products by retaining the same overall volume of fat droplets within the microstructure of the food while reducing the actual fat content by displacing some it with internalized water so that the total calorific value of the fat within the food is reduced. For example, this can be used to produce cheeses with reduced fat that can trick our tongues into believing that there is more fat in the product.

Technologies used in the research.

The functionalization of milk streams involves the use of processing technologies to control the fat and/or protein interactions in milk.

To produce double emulsions, we need to be able to disperse fat into water (and vice versa) effectively and efficiently, and to do this we use several novel processing technologies. One such technology is ultrasound, which involves the application of high-frequency oscillating sound waves into a fluid to initiate the violent collapse of microbubbles within the fluid. The collapse of these bubbles, a process known as acoustic cavitation, generates a large amount of energy in the form of intense mixing and shearing, which can be harnessed to facilitate the efficient dispersion of tiny emulsion droplets into a bulk continuous phase. The powerful collapse events also generate temperature hot-spots within the fluid, which can facilitate partial denaturation/modification of the proteins present in milk. This partial denaturation is critical to the formation of stable emulsions, as it enables the proteins to provide higher emulsifying stability.

Another processing technology to produce emulsions is known as high-pressure homogenization where we force fluid to move through a narrow valve opening. As it passes through the opening, the liquid experiences a large change in pressure, generating intense shearing and mixing forces. These forces are, again, very useful for the generation of tiny emulsion droplets.

The proteins that are in dairy streams play a key role in their functionality. In milk systems, there are 2 main classes of proteins, these being the casein and whey proteins. Casein and whey proteins differ markedly in their functional characteristics, eg. heat stability, solubility, gelation properties. One of our project goals is to understand how to tailor milk streams to achieve a desired functional character e.g. improved heat stability and gel formation, by specifically manipulating the interactions between casein and whey.

To understand and study their interactions on a fundamental level, we fractionate these proteins from milk through a separation process known as microfiltration. This process involves passing milk through a membrane filter with a controlled pore size of ~0.1 μm. Casein proteins, which are present in milk as aggregates that are generally larger than 0.1 μm, do not pass through the membrane, whilst whey proteins which are much smaller, do pass through the membrane, enabling their specific separation from milk.

We make use of ultrasound, high pressure, and heat treatment to specifically modify desired characteristics of dairy proteins in milk. For example, we have found that it is possible to enhance the gel-forming kinetics of milk streams, by applying strong shear from ultrasound especially to casein protein.

Stabilizers used to produce double emulsion cheese.

Cheese is a tasty food product that many of us enjoy. Much of the texture and creamy flavour of cheese, is contributed by its fat content, which unfortunately for those of us trying to maintain a healthy weight, is very high. Low-fat cheeses, which have a lot of fat removed, do not taste as creamy and tend to have an undesirable rubbery texture. A double emulsion cheese is essentially a cheese that contains the same volumetric contribution of fat in its food structure, but because the fat is displaced with an inner volume of water droplets, the actual calorific content of the cheese is reduced. By doing so, we can create cheeses with sensory profile and texture similar to full-fat cheese, but with reduced fat content.

The types of emulsifiers we use to create our double emulsions are food grade emulsifiers (in small concentrations) or are naturally present in milk. One of the ways we have been able to reduce the number of emulsifiers required to create our double emulsions is to make use of the proteins present in milk to stabilize fat droplets. The bigger challenge for double emulsions is to stabilize water droplets in fat, but we have found an effective combination of proteins (e.g. casein and whey proteins), food grade emulsifiers (eg, polyglycerol polyricinoleate) and phospholipids (e.g. lecithins) to facilitate this stabilization.

Uniqueness of the research.

Low-fat cheeses that taste better are attractive to consumers and hence are a lucrative opportunity for dairy producers. Some examples of methods to improve low-fat dairy products include the microparticulation of protein into cheese to mimic the presence of fat globules, or to try to increase the overall moisture content of a low-fat cheese so that the texture of the cheese is less hard. These techniques, however, may affect other flavour properties of a cheese e.g. increased bitterness, rancidity development etc., as the additives interact directly with the cheese microstructure

Double emulsion cheeses attempt to retain the same volumetric fat content, but the water droplets are ‘hidden away’ within the fat droplets themselves. In this way, there is a minimal interaction of the water with the cheese microstructure, and the size of the fat droplets is the main contributor to improved cheese texture.

One of the challenges of double emulsions is they often require the use of large amount of emulsifiers, which in food products, is not desirable. We are aiming to address this disadvantage of double emulsions by utilizing the proteins naturally present in milk streams to stabilize the emulsions, reducing requirement for additional emulsifiers.

Challenges faced during the research.

Formulating stable double emulsions with minimal non-dairy additives is a challenge but one that we are beginning to address with our combination of novel processing technologies and knowledge of protein/fat interactions. The ultimate goal would be to produce double emulsions with no emulsifier additives, which would enable the creation of clean-label, healthy, low-fat products that taste fantastic.  

Research benefit for the dairy industry.

Fat is a valuable dairy resource. If high-quality cheese can be made using less fat by using the double emulsion technology, this fat can be utilized in other products or be used to make more product, thereby enhancing the potential revenue. As mentioned, the ability to make low-fat cheeses taste better may open up new lucrative markets that will add value to the bottom line for producers.

Commercializing the technology.

We are currently working closely together with a number of dairy companies in Australia as part of the ARC Dairy Innovation Hub to advance our double emulsion technology towards marketable products.

Plans for future research.

We plan to investigate the viability of incorporating double emulsions into a range of cheese and other functional dairy products. The success of these products will be underpinned by fundamental research we are doing in parallel with product development and sensory analysis, to better understand how to improve key properties in these products.

Areas in the dairy industry with research potential.

Value-added products are critical to differentiating from simple low-value, high-volume streams eg. skim milk powder. Higher valued products are very important to improve profit margins in a very competitive global industry where fluctuating milk prices can erode the bottom line for milk producers and processers.

© Chemical Today Magazine


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