Impact of processing conditions on microstructure, texture and chemical properties of model cheese from sheep milk

Abstract

Cutting and cooking settings have a strong effect on curd particle features, whey syneresis and cheese properties. In the present study, the impact of curd grain size and cooking temperature on the microstructure, texture and composition of cheese, whey losses and cheese yield was studied with specific focus on sheep milk. Cooking temperature especially affected cheese microstructure, texture and composition, while cutting process was largely responsible for fat losses in the whey. Additionally, cheese yield increased with a bigger curd grain size and lower cooking temperatures. Higher cooking temperatures reduced the moisture content of the curd grains and cheese and lead to cheeses with reduced porosity and more free fat in their structure, resulting in harder and chewier cheeses. Interactions between the microstructural arrangement of fat and textural parameters were also observed. These results contribute with new data on the relationships between curd grain size and cooking conditions on the microstructure and physicochemical properties of cheese. In addition, reducing the compound losses in whey would have a direct effect on the improvement of processing, cheese quality and yield, and the ulterior byproduct management.

Relationships between cheese-processing conditions and curd and cheese properties to improve the yield of Idiazabal cheese made in small artisan dairies: A multivariate approach

“…The microstructure of the curd grains significantly (P ≤ 0.05) changed during cooking but, only when high cooking intensity was used. The porosity of the protein network significantly (P ≤ 0.05) decreased (Table 3; Figure 3E and F) due to the increased syneresis (reduced SCG moisture) induced by the long time, high speed, temperature raise (38°C), and consequent pH drop during cooking (Figure 4), as observed by other authors (Ong et al, 2011;Aldalur et al, 2019b). The size, shape, and distribution of the fat droplets also changed (P ≤ 0.05) during cooking, decreasing the sphericity and the volume of globular fat, and increasing the nonglobular or coalesced fat volume (Table 3; Figure 3F, white arrows).…”

“…reported by Aldalur et al (2019b). Briefly, a minimum of 20 adjacent micrographs were used for the reconstruction of 3D images with an observation depth of a minimum of 10 μm.…”

“…Fat volume, fat globule or fat droplet diameter, sphericity, and protein-network porosity were determined. As previously described by Aldalur et al (2019b), 2 fat globule populations were defined: globular fat droplets (fat globule diameter <6 μm) and nonglobular or coalesced fat droplets (droplet diameter >10 μm). The percentage of fat volume contributed by globular or nonglobular fat was quantified.…”

“…Additionally, the time, speed, and their combination used during cutting and cooking processes also have a remarkable effect on component losses. On one hand, an excessive cutting step, either for a long process, a high speed, or both has been reported to increase whey losses (Kammerlehner, 2009;Aldalur et al, 2019b). On the other hand, the combined effect of an insufficient cutting process followed by higher stirring speed settings enhances fat and casein losses (Johnston et al, 1998;Everard et al, 2008).…”

“…Confocal laser scanning microscopy (CLSM) allows for observation and quantification in 3 dimensions of the changes in casein compaction and fat globule conformation, which could have further implications in the texture and flavor of cheese (Everett and Auty, 2017). Recently, it has been suggested that curd-grain size could be related to a higher nonglobular fat amount due to a higher level of compaction during pressing (Aldalur et al, 2019b). Additionally, cheese texture is determined by its microstructure and physicochemical composition (Lamichhane et al, 2018), but the effect of in-vat cheesemaking settings on microstructure and texture has not been widely reported.…”