Investigating casein-polymer interactions as a platform technology for cheese for Asian consumers
The focus of the global cheese industry on accessing new markets for cheese is driving a greater need for innovation in cheese products. Increasing opportunities for cheese have been identified in many Asian countries, due to factors such as rising income and a change away from traditional lifestyles (e.g., appeal of fast-food chains to young people). The objectives of the work presented in this thesis were: to gain a better understanding of consumers in emerging markets; to identify texture or flavour characteristics of cheese that may be preferred by such consumers; and to explore the potential of incorporation of different non-dairy polymers in different processing steps of cheese manufacturing to achieve such sensory properties. Consumer focus group methodology was applied to understand the preference for, and consumer behaviour towards, cheese products by a cohort of young, internationally mobile Chinese consumers. Participants in the focus groups had general positive expectations towards cheese due to associations with western-style foods and nostalgia; however, many participants had low perceived ability to select cheese and had limited motivation to engage with cheese due to low perceived relevance of cheese to their daily food life. Innovative cheese products such as cheese snacks or cheese energy bars may be developed to better fulfil important choice motives. Participants generally preferred cheese with a mild and milky flavour and a soft texture, which agreed with trends emerged from a parallel literature review. The effects of addition of konjac glucomannan (KG, neutral charge), soy soluble polysaccharides (SP, negatively charged), or chitosan (CH, positively charged) on rennet coagulation and rennet-induced casein gels were investigated to assess the potential of incorporating these polysaccharides prior to rennet coagulation to modify cheese texture. Addition of either KG (0.02%, 0.04%) or SP (0.25%, 0.5%) enhanced rennet coagulation properties by reducing rennet coagulation time (RCT) and promoting development of gel firmness. The addition of CH, on the other hand, hindered rennet coagulation by decreasing the maximum gel firming rate. The two non-interactive polysaccharides (KG and SP) affected rennet coagulation by a depletion flocculation mechanism, and hydrated KG or SP particles may act as inactive filler particles in rennet-induced gels. Larger hydrated KG particles provided weak points in the gels, while smaller SP particles did not significantly affect microstructure or properties of rennet-induced casein gels at the concentrations studied, which, combined with relatively low retention rate in curd, limits its use for modification of cheese texture. Interactions of CH with caseins hindered aggregation of hydrolysed caseins, and gave less interconnected gel structures. The incorporation of KG or CH affected rennet coagulation and gel structure through different mechanisms, but could both result in a casein matrix that is softer and more easily broken down, which may be harnessed to develop cheese preferred by Asian consumers. The effects of addition of SP/KG/CH (0.5%) at dry salting of Cheddar-style cheese manufacture on characteristics of the cheeses were examined. Addition of KG at dry salting resulted in formation of a KG gel at milled curd junctions, retaining significantly (p<0.05) higher levels of moisture and salt, and higher salt-in-moisture (S/M) level compared to the control without polysaccharide addition. A significant (P<0.05) reduction in salty whey level was also observed with addition of CH, although to a lesser extent compared to KG addition, with a concurrent significant (p<0.05) increase in salt and S/M levels. The changes in compositions of these cheeses also impacted texture and volatile compound profiles over a ripening period of 90 d, although no difference in overall consumer acceptability was observed by a cohort of Chinese consumers. Dry salting is thus a promising step to incorporate different polysaccharides into Cheddar-style cheese, which could also help with salt retention and reduction in salty whey production, as well as modifying cheese characteristics (e.g., composition and texture), which may be of interest to manufacturers and researchers from sustainability and/or product development perspective. Cheese puffs (manufactured using microwave vacuum drying: MVD) produced from Cheddar curds with or without polysaccharide addition at dry salting were characterised. MVD was shown to be a promising technology to produce dried cheese snacks with minimal changes in properties such as colour and volatile compounds. The volumetric expansion during puffing process was significantly (p<0.05) decreased by addition of KG, and increased by addition of CH, respectively; this showed that polysaccharides may be used in modifying texture of cheese puffs. Overall, the work undertaken provides a technological platform for industry to help access Asian markets and contributes to the understanding of use of polysaccharides in development of novel cheese products.
Cheese, Cheese structure, Polysaccharide, Emulsion gel, Rennet coagulation, Asian consumers, Salty whey
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