# Development and Evaluation of a Fermented Pistachio-Based Beverage Obtained by Colloidal Mill
## 3 Results and Discussion
### Volatile Organic Composition of the Fermented Pistachio-Based Beverage  
The fermented pistachio-based beverages were further analyzed for their volatile compound profile. The HS-SPME-GC/MS analysis of the samples detected the presence of major and minor volatile compounds, recognized as being responsible for the aroma of these fermented beverages. A total of 23 volatile compounds were detected, belonging to aldehydes (2), ketones (4), esters and acetates (1), acids (2), alcohols (7), terpenoids (6), and benzene derivatives (1) (Table 5). In the samples analyzed, the most detected volatile compounds belonged to ketones, terpen, and acids, whereas small quantities of aldehydes, esters, and acetates and other substances, such as methylpyrrole, were found. Aldehydes were present in small amounts and in a few samples, the most representative being 2-methylbutanal and 3-methylbutanal. Among ketones, 2,3-butanedione and acetoin were the most frequent in almost all the samples, with the exception of the control sample. Traces of 4-methyl-2-heptanone and gamma butylolactone were found. The beverages fermented with the _Leuc. pseudomesenteroides_ PD4 and _C. kimchi_ PU2 strains were characterized by the highest amount of ketones. In particular, the sample fermented with _Leuc. pseudomesenteroides_ PD4 had the highest amount of 2,3-butanedione and acetoin, compounds that are highly valued for their pleasant buttery, fatty, and fruity notes associated with a yogurt-like aroma, kefir, or a sweet cheese flavor [34]. Samples fermented by _C. kimchi_ PU2 and _L. plantarum_ PV2 were also characterized by high amounts of 2,3-butanedione and acetoin. In the beverages fermented by _L. plantarum_ PT1, _C. alimentarius_ PG3, and _L. paraplantarum_ PN4, acetoin was found in traces. It is known that acetoin and diacetyl are produced by LAB and contribute to butter flavor and aroma, especially in dairy products, so the acetoin production of different LAB such as _Leuconostoc_[52], _Lactococcus lactis_[53], and _Companilactobacillus_ and _Limosilactobacillus_ species [54] has been investigated. However, the production of butter aroma compounds in commercial plant-based fermented dairy alternatives (PBDA), including coconut, oat, rice, hemp, pea, hazelnut, and soy milk, was also determined by [PERSON] et al. (2024) [55]; these authors demonstrated significant variations in PBDA fermentation performance by using different strains. [PERSON] et al. (2024) [55] found different lactic acid bacteria species producing acetoin and diacetyl in different amounts, including _Leuconostoc_ spp., _L. paraplantarum_, _L. plantarum_, as well as _E. casselflawus_, _L. brevis_, _L. paracasei_, _L. hannosus_, _L. sakei_, and _P. pentosacus_. Furthermore, other authors [56] investigated the ability of different LAB isolates from plants to produce acetoin in the liquid fractions of brewers' spent grain. They found that strains of _Leuconostoc pseudomesenteroides_ seem to be the most suitable LAB for the production of acetoin at the highest value, with acetate as the only major by-product. Among esters and acetates, traces of ethyl lactate were only detected in the sample fermented with the strain _L. paraplantarum_ PN4.