Impact of processing conditions on microstructure, texture and chemical properties of model cheese from sheep milk
Introduction
The technological conditions used during cheese processing, particularly curd cutting and cooking process, have a direct effect on cheese composition, yield and compound losses in the whey. During cutting and cooking, syneresis of curd occurs and this is affected by several factors well documented in the scientific literature such as: milk composition, firmness of the gel at cutting, gel acidity, temperature, time of cutting, speed of rotation of the cutting and stirring tools and the surface area of the curd (Banks, 2007; Dejmek and Walstra, 2004; Everard et al., 2008; Johnston et al., 1991, 1998; Walstra et al., 2006).
While some authors (Johnston et al., 1991; Whitehead and Harkness, 1954) have suggested that the size of the curd grain plays an important role in the moisture of the final cheese product, others have found that different curd cutting intensities have little effect on the extent of syneresis, although enhanced losses of fat and casein fines were reported (Everard et al., 2008). The relationship between fat and protein losses from the curd and a reduction in cheese yield with curd grain size has been shown to be influenced not only by the cutting revolutions but by a combination of the total revolutions applied during cutting and cooking processes (Everard et al., 2008; Johnston et al., 1991, 1998). Even though cheesemaking processing conditions affect chemical properties of cheese, the studies about the interactions of cutting and cooking settings with microstructure and texture are scarce. Additionally, the comparison of cutting and stirring conditions in this prior studies is made difficult due to technical differences in the cheesemaking processes applied. In this study, the curd grain size was assessed by image analysis to provide information about the curd grain size obtained at the end of the cutting or cooking processes (Aldalur et al., 2019). This method may reduce some of the comparative issues described by other authors, such as the use of different vat designs and sizes, cutting knives, stirrers and cutting and stirring conditions (Everard et al., 2008; Johnston et al., 1998).
Temperature is another factor that enhances moisture expulsion from curd grains, as the permeability of the curd matrix increases at higher temperatures (Fagan et al., 2007). A rapid increase in temperature, however, may lead to a shrunken outer layer of the curd grain, impairing permeability and slowing syneresis (Dejmek and Walstra, 2004). Moreover, temperature greatly affects the properties of fat globules and the spatial arrangement of other components in cheese, which ultimately determine the structure of the cheese and its physico-chemical and sensory properties (Lamichhane et al., 2018; Lopez et al., 2006). As a result, the microstructural observation of cheese and samples taken during the cheesemaking process can be very useful to predict and control the properties of the final cheese product (El-Bakry and Sheehan, 2014). Confocal laser scanning microscopy (CLSM) is a powerful tool, which allows two-dimensional (2D) thin optical sections of a sample to be digitally captured and reassembled to obtain three-dimensional (3D) information (Gunasekaran and Ding, 1998). This imaging allows both fat and protein to be visualised and quantified, providing numerical information about the size, shape and distribution of key components of the curd and cheese matrix. In addition, cryo-scanning electron microscopy (cryo-SEM) provides a detailed image of the surface features of hydrated samples without chemical staining and conventional sample drying (Ong et al., 2011).
Cheese produced from raw sheep milk is particularly important in European countries such as France, Italy, Greece, Spain and Romania (EUROSTAT, 2016). This type of milk is suitable for cheesemaking due to the higher concentration of milk components and improved coagulation properties compared to cow milk (Kammerlehner, 2009; Park et al., 2007). While considerable differences have been observed, the effects of the conditions used during the cheesemaking process using sheep milk in the cheese product, compound losses and yield have been scarcely reported.
The objective of the current study was to investigate the effect of the processing parameters curd grain size, assessed by image analysis, and cooking temperature on the microstructure, texture, composition and yield of cheese from sheep milk.
Section snippets
Experimental design and sampling
A two-level full factorial experimental design was employed, which looked at the effects of curd grain size (CGS) and cooking temperature (CT) on the final cheese product (Table 1). Two levels of CGS were selected: big and small, and two levels of CT: 36 °C and 45 °C, all other cheesemaking conditions remained fixed. The four experimental cheeses were made in two consecutive days using the same bulk raw ewe milk collected from a local farm (Meredith Dairy, Truganina, Victoria, Australia) one
Curd grain size and cooking temperature
Cheesemaking experiments were performed where the curd grain size (CGS) and cooking temperature (CT) were varied to assess the impact of these parameters. The area of the large curd grains assessed by image analysis was significantly (P ≤ 0.05) greater than the area of the small curd grains (Table 1). As expected, this difference was significant for grains assessed both after cutting (FCG) and after cooking (SCG), indicating the effectiveness of the manual wire mesh technique and number of
Conclusions
This study indicates that curd grain size and cooking temperature affect the structural and textural characteristics of cheese made using raw sheep milk, in addition to affecting the yield and composition of the whey generated during the cheesemaking process. The cooking temperature had a major effect on cheese composition, increasing the dry matter content of the cheese due to the enhanced syneresis during cooking. A higher cooking temperature significantly altered the texture of the cheese,
Acknowledgements
The authors thank Meredith Dairy for supplying the milk used in this study. Financial support was provided by The University of the Basque Country (PA16/04) and The Basque Government (IT944-16) A. Aldalur thanks The Basque Government for the research fellowship. The research was supported by The Australian Research Council (ARC) Industrial Transformation Research Program (ITRP) funding scheme (Project Number: IH120100005). The ARC Dairy Innovation Hub is a collaboration between The University
References (40)
- et al.
Characterization of curd grain size and shape by two-dimensional image analysis during the cheesemaking process in artisanal sheep dairies
J. Dairy Sci.
(2019) - et al.
Cheddar cheese yields in New York
J. Dairy Sci.
(1984) - et al.
Removal of lactic acid whey using electrodialysis
Sep. Purif. Technol.
(2016) - et al.
The syneresis of rennet-coagulated curd
- et al.
Analysing cheese microstructure: a review of recent developments
J. Food Eng.
(2014) - et al.
Invited review: a commentary on predictive cheese yield formulas
J. Dairy Sci.
(2010) - et al.
Effects of cutting intensity and stirring speed on syneresis and curd losses during cheese manufacture
J. Dairy Sci.
(2008) - et al.
Cheese structure and current methods of analysis
Int. Dairy J.
(2008) - et al.
Effect of cutting time, temperature, and calcium on curd moisture, whey fat losses and curd yield by response surface methodology
J. Dairy Sci.
(2007) - et al.
Effect of milk protein standardization using different methods on the composition and yields of Cheddar cheese
J. Dairy Sci.
(2006)
The influence of cheese manufacture parameters on cheese microstructure, microbial localisation and their interactions during ripening: a review
Trends Food Sci. Technol.
Effect of various cutting and stirring conditions on curd particle size and losses of fat to the whey during Cheddar cheese manufacture in Ost vats
Int. Dairy J.
Milk fat thermal properties and solid fat content in Emmental cheese: a differential scanning calorimetry study
J. Dairy Sci.
Development of the milk fat microstructure during the manufacture and ripening of Emmental cheese observed by confocal laser scanning microscopy
Int. Dairy J.
Native vs. Damaged milk fat globules: membrane properties affect the viscoelasticity of milk gels
J. Dairy Sci.
The effect of pH at renneting on the microstructure, composition and texture of Cheddar cheese
Food Res. Int.
The addition of calcium chloride in combination with a lower draining pH to change the microstructure and improve fat retention in Cheddar cheese
Int. Dairy J.
Physico-chemical characteristics of goat and sheep milk
Small Ruminant Res.
Fat in raw milk, Babcock method, Method Nº 989.04
Cheese yield
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