90 J/g and 0.85 J/g, respectively. These authors attributed this enthalpy to gelatinization of starch and suggested that some starch granules retained their crystalline structure after extrusion under these particular extrusion conditions, since the other extrusion conditions did not present δH. Nevertheless, if this was this case, it is not possible to ascertain whether the δH is attributed to gelatinization starch or denaturation protein, ABT-888 in vivo because the starch was not pure (starch-rich fraction) and the temperature of this peak was not reported. Dynamic rheometry was employed to determine the temperature at which storage modulus increases
(TG′inc), and to ascertain storage modulus at the end of heating (G′h) and storage modulus at the end of cooling (G′c). Since the macromolecular substances responsible for network formation in BMS-354825 mouse food systems are primarily polysaccharides and proteins (Tabilo-Munizaga & Barbosa-Cánovas, 2005), the results for dynamic viscoelastic properties were interpreted taking into account the starch and protein content (around 70% and 15%, respectively). The storage and loss moduli analysis of native flours showed that the viscoelastic behavior of these
flours was characteristic of a gel, considering that G′ value was higher than G″ value (Fig. 3A and B). At lower temperatures storage modulus was lower than loss modulus, but at around 60 °C, G′ starts to increase and exceed G″. The temperature at which the storage modulus showed a sharp increase (TG′inc) was considered as the temperature the structure formation started (González et al., 2007). In fact, Carnitine dehydrogenase the native flour TG′inc values were lower (approximately 10 °C) than the Tonset values obtained on DSC analysis at the same concentration (20 g/100g). In fact, there is no consensus on the data obtained from DSC and rheometry techniques (Sandoval et al., 2009). Nevertheless, some authors (Eliasson, 1986 and ∗González et al., 2007b) hold that the initial increase of storage modulus
is related to the hydration and swelling process of the amorphous regions of starch granules, which would be in turn related to the prior development of TG′inc compared to Tonset values. Some reports in the literature state that in the specific case of starchy food products, DSC has not shown sufficient sensitivity to detect the glass transition (Champion, Le Meste, & Simatos, 2000). Based on our results, it seems that the initial swelling process is also not detected by this technique. From the above discussion, it can be concluded that in native flours TG′inc values represent starch gelatinization together with the gelation of protein that presents lower thermal stability (as outlined above). The temperature range in which the storage moduli of native flour reached the maximum values during the heating period was 75–80 °C.