Volatile Components and Preliminary Antibacterial Activity of Tamarillo (Solanum betaceum Cav.)

Abstract

Tamarillo is a nutrient-dense fruit with a unique aroma from its volatile compounds (VCs). In this study, we aimed to compare the volatile profiles: (i) of fresh and freeze-dried tamarillo; (ii) detected using Thermal Desorption–Gas Chromatography–Mass Spectrometry (TD–GC–MS) and Solid-Phase MicroExtraction–Gas Chromatography-Mass Spectrometry (SPME–GC–MS); (iii) of freeze-dried pulp and peel of New Zealand grown tamarillo. The possible antibacterial activity of freeze-dried tamarillo extracts was also investigated. We show that freeze-drying maintained most of the VCs, with some being more concentrated with the loss of water. The most abundant VC in both fresh and freeze-dried tamarillo was hexanoic acid methyl ester for pulp (30% and 37%, respectively), and (E)-3-Hexen-1-ol for peel (36% and 29%, respectively). With the use of TD–GC–MS, 82 VCs were detected for the first time, when compared to SPME–GC–MS. Methional was the main contributor to the overall aroma in both peel (15.4 ± 4.2 μg/g DW) and pulp (118 ± 8.1 μg/g DW). Compared to water as the control, tamarillo extracts prepared by water and methanol extraction showed significant antibacterial activity against E. coli, P. aeruginosa, and S. aureus with zone of inhibition of at least 13.5 mm. These results suggest that freeze-dried tamarillo has a potential for use as a natural preservative to enhance aroma and shelf life of food products.

Effect of Tamarillo Fortification and Fermentation Process on Physicochemical Properties and Nutrient and Volatiles Content of Yoghurt

“…These esters mainly originate from tamarillo [ 44 , 45 , 46 ] and can minimize the sharpness and bitterness imparted by fatty acids and amines in yoghurt [ 41 ]. The concentration of ethyl hexanoate in fortified yoghurts was significantly lower than the original amount present in tamarillo fruit [ 16 ]. This may have been due to the matrix effect of yoghurt, where proteins and exopolysaccharides, as well as physicochemical interactions between components like pectin and sucrose, affect the release of volatile compounds [ 42 ].…”

“…A 1–2 g yoghurt sample was quickly introduced into a 10 mL headspace vial. Ten μL of internal standard (6.5 mg/L solution of dichlorobenzene in water) was added to the vial and vortexed for 30 s. GC-MS coupled with SPME fibre was used for volatile analysis according to our previous study [ 16 ]. The total run time was 37 min.…”

Essential Oils and Their Major Components: An Updated Review on Antimicrobial Activities, Mechanism of Action and Their Potential Application in the Food Industry

“…Several researchers have examined the antibacterial activity of various other fruit peels such as tamarillo [60], bergamot (Citrus bergamia) [57,61], sweet lemon (C. limetta) [53,62], C. deliciosa [63], kumquat (C. japonica) [64] and feijoa (Acca sellowiana) [65]. Surprisingly, Diep et al [60] and Mandalari et al [61] revealed that the tamarillo and bergamot peel flavonoids, respectively, exhibited strong antibacterial activity against Gram-negative bacteria such as E. coli, Pseudomonas putida, S. enterica serovar Typhimurium and P. aeruginosa, while Gram-positive bacteria (B. subtilis, L. innocua, S. aureus) were resistant. Similarly, El-Hawary et al [63] found that C. deliciosa EO extracted from its leaves and peel was more effective against Gram-negative bacteria than the Gram-positive bacteria.…”

“…Due to the difference in their cell wall structure [34], Gram-positive bacteria are more susceptible to EOs than Gram-negative bacteria [23,40,54,66]. However, published data have shown no clear differentiation between Gram-positive and Gram-negative bacteria [60,63]. The reason for this contradictory result is discussed in Section 4.…”

Nutritional and Volatile Characterisation of Milk Inoculated with Thermo-Tolerant Lactobacillus bulgaricus through Adaptive Laboratory Evolution

“…Volatile components of the inoculated milk samples were analysed according to the methods used by the same research group [ 27 ] with slight modifications.…”