Search

[Display omitted] • GSP roasting generally increased the abundance of PAC with DP ≤ 10. • Red varieties GSP had an increase in all PAC classes upon roasting except trimers. • Ortrugo GSP did not show a change of DP profile of PACs upon roasting. • Cyclic PACs were identified for the first time in GSP. • Cyclic PACs in GSP were unaffected by the roasting. Grape seeds are a valuable source of natural phenolic compounds, particularly flavan-3-ol derivatives such as condensed tannins. Recent studies have shown that grape seed powder can be applied to reduce the undesirable effects of protein instability in wine. One pretreatment method applied to grape seeds is roasting. Roasting causes the heavier proanthocyanidins (PAC) oligomers to break down, thereby increasing the concentration of smaller oligomers available for interaction with proteins. In addition, roasting can prolong grape seed storage. Among the subclasses of proanthocyanidins, oligomeric macrocyclic proanthocyanidins have also shown potential effects in terms of wine stabilization, particularly by presenting selective interactions with metal cations such as potassium and calcium. However, their composition in grape seed extracts has never been studied. Here, the characterization of condensed tannins according to the degree of polymerization in grape seeds, the profile of cyclic proanthocyanidins and the total polyphenol content were characterized in relation to different grape varieties and the application of roasting. Roasting greatly influenced the distribution of PAC according to the degree of polymerization, increasing the abundance of almost all classes of PAC. However, the overall effect of roasting was highly dependent on grape variety. PAC were analyzed according to the degree of polymerization. Grape seed roasting of red varieties (Croatina and Sangiovese) showed an increase in all classes of PAC except trimers. The white variety (Ortrugo) and the mix of Nebbiolo and Barbera varieties (80% and 20% w/w, respectively) showed no clear effect on the profile of PAC upon roasting. Notably, cyclic procyanidins were identified for the first time in grape seeds: a cyclic tetrameric procyanidin (ESI + m / z 1153) and cyclic pentameric procyanidin (ESI + m / z 1441) were found. The abundances of these cyclic PAC were found to be completely stable upon roasting, also in agreement with the already known stability of these compounds against depolymerizing conditions. Interestingly, the cyclic pentameric procyanidin was significantly more abundant in Ortrugo (white variety), than in Sangiovese and Croatina (red varieties). Besides, no effect of roasting occurred on the profile of cyclic procyanidins in grape seed powder. Finally, the total polyphenol content was evaluated, showing that roasting caused an increase of polyphenolic molecular species potentially available for protein stabilization, but only in GSP of red varieties. Overall, the grape variety was found to be a significant factor in determining how much the roasting would change the PAC profile, providing valuable information for future applications of GSP in enology. [ABSTRACT FROM AUTHOR]

A ne\Y functional processed cheese fortified with grape seed powder (GSP) and its extract (GSE) was developed. The chemical composition, physical, microbiological properties, texture profile and sensory evaluation of prepared processed cheese were followed throughout storage period at 5°C up to 3 months. The moisture, ash, fat/dry matter (F/DM) and protein dry matter (P/DM) of supplemented processed cheeses were higher compared to control. While salt/moisture (SIM) content was lower. Addition of GSP and GSE increased the pH, SN and antioxidant activity, but decreased the TVFA values and total bacteria count (TBC) compared with control, throughout storage. Significant differences were found between treatments and control processed cheese in texture profiles. Cheese fortified with up to 0.3% GSP and GSE exhibited better appearance, texture &body and flavour. Further increase in the added ratio, significantly decreased the sensory scores compared with control. [ABSTRACT FROM AUTHOR]