Increasing the protein content of yogurts would be a good strategy for enhancing their satiating ability. However, the addition of protein can affect product palatability, contributing astringency or an inhomogeneous texture. Increasingly, studies mimicking oral tribology and oral lubrication have been attracting interest among food researchers because of their link with oral texture sensations. In the present study, four double-protein stirred yogurts were prepared by adding extra skimmed milk powder (MP) or whey protein concentrate (WPC) and by adding a physically modified starch to each (samples MPS and WPCS, respectively) to increase the consistency of the yogurts. The lubricating properties of the four yogurts were examined by tribological methods with the aim of relating these properties to the sensory perception described by flash profiling. Samples were also analysed after mixing with saliva. The tribology results clearly showed that addition of starch reduced the friction coefficient values regardless of the type of protein. Saliva addition produced a further decrease in the friction coefficient values in all the samples. Consequently, adding saliva is recommended when performing tribology measurements of foods in order to give a more realistic picture. The sensory results confirmed that the addition of starch reduced the astringent sensation, especially in sample WPC, while the MP and MPS samples were creamier and smoother. On the other hand, the astringency of sample WPC was not explained by the tribology results. Since this sample was described as “grainy”, “gritty”, “rough”, “acid” and “sour”, further studies are necessary to investigate the role of the number, size, shape and distribution of particles in yogurt samples, their role in astringency perception and their interaction with the perception of the tastes mentioned. Oral tribology has shown itself to be an in vitro technique that may aid a better understanding of the dynamics of in-mouth lubrication and the physical mechanisms underlying texture and mouthfeel perception.

The principal motivations for the worldwide trend towards reducing meat consumption are health, the environment and animal welfare. The present study investigated the willingness of omnivores to introduce mixed (beef-vegetable protein) and 100% vegetable protein products into their diet. The participants (n = 251) were young adult omnivores who consumed meat at least once a week. The stimuli were images of six different products representing two beef burgers, two mixed-protein burgers (50% beef and 50% seitan or soy) and two 100% vegetable protein burgers (seitan and soy). The participants were asked to write down spontaneous associations with each product (Word Association technique) and score their expected liking and purchase intention for them. In addition, they completed a questionnaire (36 statements) to evaluate their attitude towards meat reduction, considering six aspects: diet, habits, ethics, hedonism, health, and the environment. According to their response to these statements, they were classified into three attitude groups: anti- (ANTI, n = 106), intermediate- (INTERM, n = 89), and pro- (PRO, n = 56) meat reduction. All the participants expected to like the 100% beef burger most, the PRO group expected to like all six products to a similar degree and the ANTI group expected to like the mixed product significantly more than the 100% vegetable product, indicating that the introduction of mixed proteins could be a small first step towards meat reduction for those most attached to meat. The associations elicited by the different burgers were mostly the same but were mentioned with different frequencies, which also depended on the attitude group. These distinctive association patterns showed clear connections to the motives underlying each group's attitude towards meat reduction. It may be concluded that mixed products would be a reliable although timid option for consumers who are attached to meat to reduce their meat intake, while any of the products containing vegetable proteins would be an option for consumers who are more favourable towards meat reduction.