## 3 Results and Discussion
### Volatile Compound Profile of Non-Fermented and Fermented Apple Juice and Cider Samples  
The main VC in non-fermented frozen AJ are shown in Figure 2; the whole VC profile is given in Table S1. More than 60% of all the VC in non-fermented frozen AJ were accounted for by acetic acid, butyl ester (10.9%), 1-hexanol (30.7%), and acetic acid, hexyl ester (18.7%). Acetic acid, butyl ester possesses a sharp, etherial, diffusive, fruity banana odour. The odour of 1-hexanol is pungent, etherial, fused oil, fruity and alcoholic, sweet with a green top note. The odour of acetic acid, hexyl ester is described as green, fruity, sweet, fatty, fresh, apple, and pear. The content of butanoic acid, hexyl ester in non-fermented frozen AJ was higher than 5.0%. The odour of this VC is described as green, fruity, esters, and vegetative with a waxy nuance. Other VC which are shown in Figure 2 were found in quantities lower than 5% but higher than 1% (1-butanol (3.3%), butanoate <butyl-> (3.6%), 1-octanol (4.6%), 1,3-octanediol (2.9%), cyclootene, 3-ethenyl- (1.0%), nonanoic acid (2.3%), 2-pyrazoline, 3-ethyl-1-isopropyl- (1.0%), and butyl caprylate (1.4%)). The odour of 1-butanol is fused oil, sweet balsam, and whiskey; butanoate <butyl-> has a pleasant aroma, being used in the flavour industry to create sweet, fruity flavours that are similar to that of pineapple. The odour of 1-octanol is waxy, green, citrus, aldehyde, and floral with a sweet, fatty, coconut nuance. The odour of 1,3-octanediol is musty; that of nonanoic acid is waxy, dirty, and cheesy with a cultured dairy nuance. The odour of butyl caprylate is described as buttery, etherial, herbal, and dank. The content of the other VC (in total, 14.4% of the whole VC profile), the individual content of which was lower than 1%, are given in Table S1. The main VC of C samples are shown in Table 12; the whole VC profile is given in Table S2. An increase in the content of 1-butanol, 3-methyl-; 1-hexanol; hexanoic acid; hexanoic acid, ethyl ester; octanoic acid; octanoate <ethyl->; nonanoic acid; 1-decanol;  
Figure 2: Volatile compound profile (% from the total volatile compounds) of non-fermented frozen apple juice. decanoate <ethyl>; and 7,9-di-_tert_-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione increased the overall acceptability of the C samples and positive correlations were found between overall acceptability and the above-mentioned VC (r = 0.5170, r = 0.8552, r = 0.6128, r = 0.5382, r = 0.6878, r = 0.6066, r = 0.1811, r = 0.1741, r = 0.2913, and r = 0.4030, respectively). 1-Butanol, 3-methyl- possesses a fusel, alcoholic, pungent, etherial, cognac, fruity, banana, and molasses odour. The odour of 1-hexanol is pungent, etherial, fusel oil, fruity, and alcoholic, sweet with a green top note. Hexanoic acid has a sour, fatty, sweaty cheese odour; a description of the odour of hexanoic acid, ethyl ester is given above. Octanoic acid has a fatty, waxy, rancid, oily, vegetable, cheesy odour and octanoate <ethyl-> possesses a waxy, sweet, musty, pineapple, and fruity odour with a creamy, dairy nuance. The odour of nonanoic acid is waxy, dirty, and cheesy with a cultured dairy nuance; that of 1-decanol is fatty, waxy, floral, orange, sweet, clean, and watery. The odour of decanoate <ethyl-> is sweet, waxy, fruity, and apple; and 7,9-di-_tert_-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione is one of the aroma components in mushrooms. The main VC in fermented AJ are shown in Table 13; the whole VC profile is given in Table S3. It was established that increasing the content of some of the VC increased the overall acceptability of the samples and positive correlations were found between overall acceptability and 1-butanol (r = 0.3239), butyrate <ethyl-> (r = 0.3239), acetic acid, butyl ester (r = 0.4962), butanoate <butyl-> (r = 0.4668), acetic acid, hexyl ester (r = 0.3018), 1-octanol (r = 0.5051), nonanoic acid (r = 0.2627), 2-pyrazoline, 3-ethyl-1-isopropyl- (r = 0.2488), \(n\)-decanoic acid (r = 0.8445), and 7,9-di-_tert_-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione (r = 0.6617).