The influence of raw materials, commercial yeast and nitrogen addition on cider quality

In this study, the effects of the nitrogen addition and commercial dry yeast on cider fermentation obtained from fresh and concentrated apple juice were investigated. Fresh apple juice was produced from Golden Delicious cultivar. Experiments were performed by spontaneously and inoculated with commercial dry yeast. Fermentations were performed at 18°C. Fermentations were daily monitored by a drop in specific gravity and pH. Also, the enumeration of yeast population was done. According to the results obtained, nitrogen addition led to increase for the utilisation of sugar and fermentation rates. Specific gravity dropped faster in nitrogen added musts compared to others. The maximum numbers of total yeast and non-Saccharomyces yeast in nitrogen added trials were counted as 9.62 log CFU/mL and 6.28 log CFU/mL on day 2, respectively. The pH values were slightly decreased and ranged from 3.12-3.27 at the end of the fermentation. Extraction of aroma compounds in ciders was made by using liquid-liquid extraction method. Identification and amount of aroma compounds were made using GC-MS-FID. 55 aroma compounds were determined, including 13 higher alcohols, 13 ethyl esters, 5 acetate esters, 9 volatile acids, 3 six-carbon alcohols, 5 phenolic compounds, 4 lactones and 3 carbonyl compounds. The overall quantity of aroma substances were identified as 85.18 mg/L in C1, 89.14 mg/L in C2, 72.8 mg/L in C3, 74.65 mg/L in C4, 75.26 mg/L in C5, 66.92 mg/L in C6, 62.4 mg/L in C7 and 70.3mg/L in C8 cider (p<0.05). According to the results of sensory analysis, C7 cider was ranked the highest followed by C6 and C5. Fruity and floral odours were dominant aroma in the ciders according to sensory analysis. Finally, C7 cider was valued as the best one.