## 3 Results
### Volatile Organic Compounds  
As expected, kiwifruit and cheeses were different in terms of the quantity and quality of the odorant compounds (Table 4). The total amount of VOCs from the kiwifruits was about seven times higher than from the cheeses. The most represented category of odorants in kiwi were aldehydes (about 85% of total VOCs), and carboxylic acids and ketones in the cheeses (65% of total VOCs). More specifically, (E)-2-hexenal and hexanal were the most abundant odorants in the kiwi extracts used in this experiment. These volatile aldehydes are produced during fatty acid oxidation by the lipo-oxygenase enzyme [31]. Other substances affecting odour were the ethyl esters of butyric and caproic acids, two alcohols (2-hexen 1-ol and 1-hexanol) and one ketone, 1-penten-3-one (Table 4). In terms of cheese, the most represented odorant was 2-butanone (a ketone), which was above 25% of the total VOCs in all the cheeses, followed by acetic acid, 2,3-butenedione (another ketone), caproic, caprylic and nonanoic acids (carboxylic acids). 2-butanone and 2,3-butenedione were not detected in the kiwi pulp, while acetic, caproic, caprylic and nonanoic acids were identified both in the kiwi pulp and in the buffalo and sheep cheeses produced, and both using calf rennet and kiwifruit extract. On the other hand, caproic, caprylic and nonanoic acids are typical components of both buffalo [32] and sheep milk [33]. Terpenes are typical components of kiwi pulp but not of cheese (except for \(\beta\)-phellandrene). Of the odorants that most characterize kiwifruit, in both buffalo and sheep cheeses we found only (E)-2-hexenal (representing about 80% of VOCs in pulp kiwifruit), ethyl caproate and 2-hexen-1-ol. Interestingly, in the kiwi-cheeses we found 3-methyl eicosane and dibutyl formaldehyde, which were found only in low quantities in the kiwi extract. Finally, cheesemaking was a significant variation factor for the total esters only in buffalo cheese, 3-pentanone 2-hydroxy and \(\beta\)-phellandrene, which was the only terpene we detected in the cheeses. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multirow{2}{*}{**Kiwi**} & \multicolumn{8}{c}{**Buffalo**} & \multicolumn{8}{c}{**Sheep**} \\ \cline{3-10}  & & \(\mathbf{BM_{C}}\) & \(\mathbf{BM_{K}}\) & SEM & \(\mathbf{S}\) & \(\mathbf{SM_{C}}\) & \(\mathbf{SM_{K}}\) & SEM & \(\mathbf{S}\) \\ \hline
**Acids** & & & & & & & & & \\ Acettic acid & 4.00 & 9.06 & 9.06 & 2.58 & ns & 2.58 & 3.03 & 0.43 & ns \\ Butyric acid & 1.56 & 2.26 & 1.58 & 0.48 & ns & 2.72 & 3.27 & 0.74 & ns \\ Caproic acid & 3.22 & 6.28 & 3.63 & 1.34 & ns & 7.65 & 9.65 & 2.38 & ns \\ heptanoic acid & 1.31 & 0.95 & 1.11 & 0.16 & ns & 0.79 & 0.57 & 0.07 & * \\ caprylic acid & 2.31 & 6.17 & 7.23 & 2.88 & ns & 10.53 & 13.95 & 2.83 & ns \\ n-nonanoic acid & 3.55 & 4.97 & 3.34 & 1.04 & ns & 3.83 & 4.83 & 0.83 & ns \\ n-decanoic acid & 1.69 & 1.78 & 2.61 & 0.76 & ns & 5.36 & 8.21 & 1.60 & ns \\ _Total_ & 17.64 & 31.46 & 28.56 & 6.77 & ns & 33.46 & 43.50 & 8.21 & ns \\ \hline
**Alcohols** & & & & & & & & & \\
2-methyl-3-pentanol & - & 1.00 & 2.03 & 0.28 & * & 2.15 & 0.58 & 0.14 & *** \\
2-methyl-1-undecanol & - & 1.39 & 1.98 & 0.53 & ns & 1.83 & 0.90 & 0.13 & *** \\
2-butyl-1-octanol & - & 0.77 & 0.81 & 0.19 & ns & 1.65 & 0.88 & 0.35 & ns \\
1-pentanol & 2.92 & 0.51 & 0.49 & 0.06 & ns & 0.87 & 1.29 & 0.16 & * \\
1-hexanol & 11.12 & 1.31 & 0.91 & 0.16 & ns & 0.67 & 0.91 & - & ns \\
3,4-hexane diol & - & 3.31 & 6.11 & 1.26 & ns & 3.67 & 9.52 & 0.98 & ** \\
3-hexen-1-ol & 1.67 & - & - & - & - & - & - & - & - \\
2-hexen 1-ol & 12.96 & - & 0.34 & 0.05 & ne & - & 0.46 & 0.07 & ne \\
1-octen-3-ol & 0.99 & 0.30 & 0.49 & 0.03 & ** & 0.11 & 0.15 & 0.01 & * \\
2,4,7,9-tetramethyl-5-decyne-4,7-diol & 1.49 & 2.84 & 0.82 & 0.23 & *** & 1.61 & 2.73 & 0.77 & ns \\ _Total_ & 31.11 & 11.42 & 13.97 & 1.64 & _ns_ & _12.56_ & _17.41_ & 1.79 & ns \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Volatile organic compounds of chees made with kiwifruit extract or calf rennet (ug/kg of raw matter) (Part 1).