Tannin, pellicle effects

Many foods obtained from plants contain tannins. These are phenolic compounds that bind proteins, such as mammalian enzymes. It has been shown in vitro that tannic acid significantly reduces the lubricating qualities of human saliva both by decreasing its viscosity and increasing friction [55], This effect depends on the presence of salivary PRPs, which have a high affinity for tannins [56], It has been shown that the introduction of tannins into the diet can stimulate the production of PRPs in the saliva of rats [57], PRPs are a major component of salivary pellicle, and thus it would not be surprising to find that dietary tannins affect the viscosity of pellicle. 

Pellicle and tea-immersed pellicle were analyzed using nanoDMA (dynamic mechanical analysis) to see if the tannins had an effect on the viscoelasticity of the pellicle. NanoDMA is a technique used to study and characterize mechanical properties in viscoelastic materials. The method is an extension of nanoindentation testing [58, 59], An analysis of the nanoindentation load-depth curve gives the hardness (H) and reduced elastic modulus (E ), provided the area of contact, A, between the indenter tip and the sample is known [ 13]. By... 

In contrast to walnuts and pistachios, almond pellicle contains no hydrolysable tannin and therefore no gallic acid was detectable in the cultivars Nonpareil and Mission. This is consistent with their propensity to accumulate aflatoxins [9] and their ability to support aflatoxin biosynthesis. However, there are considerable differences in aflatoxin production in vitro between cultivars and these must be due to compounds other than hydrolysable tannins. Almond pellicle has been shown to contain other phenolic constituents, primarily phenolic acids and flavonoids, which may suppress aflatoxin production although less effectively than the tannins [27-29],... 

---