The effect of cropload on the volatile aroma characteristics of ‘Beihong’ and ‘Beimei’ red wine

Abstract

Beihong and Beimei were bred as winemaking cultivars released by Institute of Botany, the Chinese Academy of Sciences in 2008. The cultivars are selected from the population of ‘Muscat Hamburg’ (Vitis vinifera) ×V. amurensis. They are extended to most provinces in North of China because they have strong resistance to cold and disease and need not be buried in soil in winter. To better understand the effect of cropload on volatile compounds during wine-making, we surveyed volatiles composition and content of different cropload level in 3-years-old ‘Beihong’ and ‘Beimei’ vines which planted in east foot of Helan mountain of Ningxia (EHN). The cropload were controlled at 3 t, 5.2 t and 7.5 t/ha for ‘Beihong’, 3 t, 4.5 t and 6 t/ha for ‘Beimei’, respectively, through thinning clusters at the 2nd July in 2014. All clusters were sampled in 29th September. The volatiles compound were surveyed in ripening berry (RB), during fermentation processing (FP), completed fermentation (CF) and after 5 months of wine clarification (5MC). The lower cropload level had the less volatiles content in RB. The total volatile contents were 494.5, 1077.9 and 1610.9 µg/kg FW in 3 t, 5.2 t and 7.5 t/ha cropload in the berries of ‘Beihong’ and 1268.6, 1920.9, 3997.7 µg/kg FW in cropload of 3 t, 4.5 t and 6 t/ha for ‘Beimei’, respectively. During FP, the volatile compositions and contents increased sharply in all cropload levels in both cultivars, and increased more quickly in low cropload than that in high cropload. They increased 95.5, 45.5 and 29.3 times (in ‘Beihong’), and 34.2, 20.7, 8.8 times (in ‘Beimei’) from low to high cropload, respectively. The total volatile contents of low cropload were close or exceed to the high cropload when fermentation finished in both cultivars. During 5MC, the volatile compositions and the contents were reduced largely. The volatiles reduced more slowly in low cropload than that in high cropload. The remained total volatile contents after 5MC were 10.3%, 9.1% and 8.9% in ‘Beihong’, and 11.3%, 10.1% and 10.5% in ‘Beimei’, respectively. Consequently, the total volatile contents in low cropload were higher than that in high cropload in both cultivars. Thirty one and 35 volatile compounds were detected in ‘Beihong’ and ‘Beimei’ wine before bottling, respectively. Among these compounds, esters were dominant (86.3%-89.8% and 78.3%-87.3% of the total volatile in ‘Beihong’ and ‘Beimei’, respectively), and followed by alcohols (8.8% – 10.8% and 7.7%- 10.2%, respectively). In addition, two terpenoids compounds (1,6-Octadien-3-ol, 3,7-dimethyl- and 2,6-Octadien-1-ol,3,7-dimethyl-, (Z)-. 2) were found in ‘Beimei’ wine. The blind wine tasting showed that the assessment scores were higher in 3 t, 5.2 t /ha cropload than 7.5 t/ha cropload for ‘Beihong’, and 3 t /ha cropload was highest in ‘Beimei’.