Evolution of tryptophan and its foremost metabolites’ concentrations in milk and fermented dairy products

Rapid Determination of Total Tryptophan in Yoghurt by Ultra High Performance Liquid Chromatography with Fluorescence Detection

“…However, Yılmaz and Gökmen [37] observed the presence of TRP, together with its derivatives, in the kynurenine pathway in commercial yoghurts, suggesting a fermentation effect on the level of TRP and its derivatives. Similar findings were reported also by Bertazzo et al [47], who observed TRP and its derivatives in both the serotonin and kynurenine pathways in milk and fermented dairy products. The authors also reported an increase in the free TRP levels with increasing fermentation, due to the proteolytic action of the added cultures, thus corroborating the hypothesis of Yılmaz and Gökmen [37].…”

“…On the contrary, our results are very high compared to those reported by Bertazzo et al [47] on similar food items (TRP = 0.7 µg/mL in yoghurt samples); the main difference is due to the fact that the authors [47] did not hydrolyze the commercial yoghurt samples, but carried out the HPLC analysis on the supernatants directly after centrifugation, so their results referred to the "free" TRP content of yoghurts. Furthermore, Yılmaz and Gökmen [48] reported similar results for free TRP in commercial yoghurts, with values ranging between 3.2 and 13.4 mg/kg dry weight.…”

“…Furthermore, Yılmaz and Gökmen [48] reported similar results for free TRP in commercial yoghurts, with values ranging between 3.2 and 13.4 mg/kg dry weight. The differences in the free amino acid contents observed by the authors [47,48] could be due to the different microorganisms involved in the production of the yoghurts, since free amino acid content has been shown to be influenced by the interactions between the microorganisms involved in the yoghurt fermentation [48], and by the different strains of the microorganisms employed [49].…”

“…However, yoghurt's shelf life is longer than milk's, and yoghurt can also be consumed by lactose-intolerant people. Furthermore, according to the study of Bertazzo et al [47], the TRP content in yoghurt does not decrease during the storage, so the TRP intake is guaranteed until the expiration date of the yoghurt. For all these reasons, yoghurt can be considered a good source of TRP, and its consumption should be encouraged, not only for ensuring the recommended daily intake of TRP, but also for its overall nutritive value, above all the probiotic properties and the calcium intake.…”

Development of Functional Dairy Foods

“…The effects on glucose metabolism seems to be mainly related with the improvement of glucose metabolism and insulin sensitivity, and reduction of muscle soreness [14,46]. The positive effects on inflammatory bowel diseases and other immune-related pathologies, including arthritis, sclerosis, fibromyalgia, migraine, and depression have been also increasingly evident, as also their modulatory effects at a level of brain and mood [14,49], still, however, being essential to deepen knowledge on this field. All the above described biological effects are briefly summarized in the Table 4.…”