# Does Organic Farming Increase Raspberry Quality, Aroma and Beneficial Bacterial Biodiversity?
## 4 Discussion
### Volatilome and Bacterial Contribution to Fruit Aroma  
Raspberry aroma is a key component for consumers' perception of sensory quality [5]. Monoterpenes are the largest class of compounds, among which terpinen-4-ol, geraniol, linalool, limonene, nerol, \(p\)-cymene, terpinolene, \(\alpha\)- and \(\beta\)-phellandrene, \(\gamma\)-terpinene and \(\alpha\)- and \(\beta\)-pinene are the most frequently reported [5]. However, only few of the several VOCs identified in the literature are recognized as important descriptors of raspberry aroma, namely 4-(4-hydroxyphenyl)butan-2-one (also known as raspberry ketone), which contributes to the pure raspberry aroma; \(\alpha\)-ionone and \(\beta\)-ionone (whose odour is described as violet-like), which are responsible for the overall fruit aroma [97]. In this work, raspberry ketone could not be detected because its linear retention index (LRI) lies outside the detection limit of this work. Interestingly, IPM fruits were richer in \(\beta\)-ionone and 5-methylfurfural. The first compound is characterized by sweet and fruity odour, with seedy nuances, whereas the second one typically has almond and cherry notes. These VOCs possibly conferred more intense floral and fruity notes to the aroma of IPM fruits, which were also characterized by the presence of hexanal. The presence of this compound, a green-odour leafy compound, conferring grassy notes to fruit aroma, corroborates the hypothesis that IPM strategy delayed ripening of berries. A higher content of 2-heptanol and _trans_-geraniol in organic raspberries was observed. Interestingly, both compounds are known for being emitted by flowers of many species and to be effective insect repellents [98; 99], thus suggesting that they have been produced as a defence-related response in organic fruit where pest attacks are less controlled. During post-harvest handling, raspberry fruits are highly susceptible, to fungal diseases, in particular grey mould caused by _B. cinerea_[100]. Remarkably, in this work IPM fruits were lacking \(\beta\)-caryophyllene, which is one of the volatile organic compounds proven to lower the susceptibility of fruits to _B. cinerea_[100]. Identification of VOCs present in raspberry fruits have been recently extensively reviewed [5]. In addition to VOCs previously described, we observed the presence of tetradecanal, 3-heptene isomers and 1-octyl acetate. The latter was found to be emitted in a significant higher amount in basil plants treated with NaCl [101]. In our work, this compound was significantly more abundant in organic raspberries which might suggest that these plants underwent and seek to react to a more stressful condition with respect to IPM ones. Overall, these results might be explained by the lack of use of pesticides and fertilizers in the organic management. Indeed, these conditions might stimulate plant self-protection mechanism and promote the synthesis of secondary metabolites in plants and fruits [102]. Bacteria produce VOCs that act as direct plant-protectants against pathogens, induce plant defences or promote plant growth and nutrition [103]. Here, we observe a difference in the microbiome and volatilome of raspberry fruits originating from different cultivation methods. Although demonstrating the bacterial origin of a particular volatile compound requires dedicated research, it is interesting to note that emission of acids by raspberry fruits is highly correlated to the presence of _Glucobacter_ bacteria (Figure 7). In our work, among the volatile compounds belonging to the acids, part of the acetic acid emitted by fruits might be of bacterial origin. Indeed, _Glucobacter_ spp. is known to colonize sugar-rich niches (such as fruit skin) and to efficiently convert sugars to acetic acid [104]. _Rosenbergella_ is a distinctive and abundant colonizer of IPM grown raspberries, here correlated with ketones and monotereness emissions. The draft genome of _R.