Formation of cheddar cheese analogues using canola oil and ultrasonication – A comparison between single and double emulsion systems

Abstract

Cheddar cheese analogues were produced from skim milk in which canola oil was emulsified using ultrasound to form either single (O/W) or double emulsions (W1/O/W2). The double emulsion cheese analogues (DECH) had a distinct microstructure and retained small skim milk droplets, dispersed in the fat phase, for more than 7 months of ageing at 4 °C. The single emulsion cheese analogues (SECH), prepared with the same fat content as control cheeses, produced comparable yields of cheese and whey, with similar composition, although the fat droplets were more spherical and showed greater coalescence. The DECH cheese with skim milk encapsulated in the oil droplets was harder, melted less and showed more free fatty acid development over 7 months of aging than the control cheeses. The SECH cheeses were softer than the control and also melted less effectively but did not show greater free fatty acid development.

Introduction

Developing reduced-fat cheeses with sensory attributes comparable with those of full-fat cheese is challenging, but has considerable commercial potential. One promising approach is the use of double emulsions (Garti, 1997), in which emulsion droplets themselves contain an inner emulsion of the opposite phase. For reduced fat cheeses, a water-in-oil-in-water type emulsion (W1/O/W2) can be used to displace some of the fat present in cheese with water. In such a system, water droplets can be emulsified within emulsified fat droplets that are themselves surrounded by the aqueous phase of the cheese.

Simply reducing the fat content by omission detrimentally affects texture, making the cheese firmer. By including water within the fat droplets, double emulsions can potentially reduce fat without significantly altering cheese structure. A double emulsion droplet can effectively occupy the same volume as a fat droplet in a regular emulsion, but with the calorific content reduced due to displacement of the oil with internalised water droplets. Double emulsions have been proposed to reduce the fat content of various food products including salad dressings (Gaonkar, 1994), Gouda cheese (Felfoul, Bornaz, Baccouche, Sahli, & Attia, 2015) and white fresh cheeses (Lobato-Calleros et al., 2006, Lobato-Calleros et al., 2007, Lobato-Calleros et al., 2008). However, achieving stability is a key challenge in the development of double emulsion products. The need for large amounts of surfactant to stabilise both the inner and outer phases (Matsumoto, Kita, & Yonezawa, 1976) has restricted the use of double emulsions in the dairy industry due to the cost and the use of non-dairy emulsifiers such as Span 80, Tween 80 (Felfoul et al., 2015), and DATEM (Lobato-Calleros et al., 2008). There are ongoing efforts, however, to use natural emulsifiers like proteins and polysaccharides as replacements for synthetic surfactants (Benichou et al., 2002, Shanmugam and Ashokkumar, 2014).

Recently, an approach that reduces the amount of synthetic emulsifier needed for stable double emulsions was reported by Leong, Zhou, Kukan, Ashokkumar, and Martin (2017) where double emulsions were prepared using sunflower oil, in which the internal water droplets were stabilised by small amounts of lipophilic emulsifier and the outer oil droplets were stabilised by proteins in the skim milk. As the bulk aqueous phase in these preparations is skim milk, this ingredient has potential to be readily transformed into cheese-like products. In principle, these emulsions could be produced with droplets of similar size to fat globules in cheese milk. This modified milk stream could then be used to create a cheese microstructure similar to that of full-fat cheese, but with the fat content reduced by the skim milk entrapped in the internal phase.

Ultrasonication is an effective method to create double emulsions with an efficiency comparable with that of conventional homogenisation and rotor stator type devices (Walstra, 1993). An advantage of ultrasound is that the applied energy density can be readily tuned to tailor the droplet size and enable a high yield of encapsulation in the double emulsions (Tang and Sivakumar, 2012, Tang et al., 2013). The ability to control droplet size could also help improve the sensory quality of reduced-fat products (Goudédranche, Fauquant, & Maubois, 2000). The ability to produce small double emulsion droplets at high yield with a high displaced volume of fat would provide complementary benefits due to the increased effective fat volume and increased surface area. Ultrasonication can also provide synergistic effects, such as partial denaturation of proteins that can help improve emulsion stability (Shanmugam & Ashokkumar, 2014). The effects of ultrasonication on protein denaturation (Chandrapala and Leong, 2015, Stathopulos et al., 2004) and/or lipid oxidation (Chemat et al., 2004, Juliano et al., 2014), however, need to be characterised further in the context of finished cheese products, as these factors can potentially affect cheese functionality and flavour development.

Double emulsions can be used to displace fat in cheese and also to replace dairy fat with less expensive oils of plant and vegetable origin. For example, canola oil is less expensive than milk fat and has a higher proportion of healthy polyunsaturated and ω-3 fatty acids. The use of non-dairy liquid oils in cheese production has to date been limited. So far, olive oil (Felfoul et al., 2015) has been used for the production of Gouda cheese, while canola oil has been evaluated in the production of soft white cheese (Lobato-Calleros et al., 2007). No study has yet evaluated the use of ultrasonically prepared double emulsions for the creation of Cheddar-cheese analogues. Furthermore, there are, to our knowledge, no prior studies that have evaluated the use of ultrasonication to produce simple emulsions formulated with liquid vegetable oils that can be converted into hard cheese-like products.

This study investigated the properties of pressed Cheddar cheese analogues created from single and double emulsions of canola oil formed using ultrasonication. The cheese analogues were compared with an established Cheddar cheese model using milk fat from cream. The effects of the ultrasonic treatment on the protein and fat content of the milk used to make cheese, the cheese itself and the whey were assessed. The microstructure and functional properties of the cheeses, including melting capability and texture were analysed. This study provides information that will be useful for developing new cheese products with a reduced and modified fat content.