Summary:
Aim/background:
Asam sunti is an indigenous fermented product of bilimbi (Averrhoa bilimbi L.) that used as an Acehnese traditional seasoning. Asam sunti has a brown color, flat oval shape, soft texture, and dry appearance. Having a specific unique flavor, this fermented fruit is widely used for seasoning in Acehnese cuisine, such as asam keueng, ikan tongkol, and sambal teri. Fermentation made asam sunti has stronger aroma than bilimbi. The potency of asam sunti as natural seasoning, especially its flavor, may increase the economically benefit of bilimbi as well as preserving the knowledge of natural flavor from local source. However, the aroma compounds in bilimbi and asam sunti have not been investigated further.
Methods:
Physical, chemical, and sensory characterization of bilimbi and asam sunti:
Color analysis was done using the Method of Hutching with Minolta CR-300 chromameter for physical characteristic. Proximate analysis done by AOAC (2002) for chemical characteristic. Quantitative Descriptive Analysis (QDA) used ASTM (1981) for sensory characteristic.
Aroma compounds of asam sunti:
Selection the best extraction method of asam sunti between maceration extraction (Wijaya et al. 2002) and Lickens-Nickerson extraction (Wijaya et al. 2002). The most resemble extract use to further analysis, GC-MS and GC-O analysis. GC-MS was used to identify the volatile compounds while GC-O was used to identify aroma compounds. GC-MS and GC-O procedure described by Pino et al. (2004). Aroma compounds were identified by nasal impact-frequency (Kirshinbaum et al., 2012). OAV calculation was used to considered potential volatile compounds that contribute to asam sunti aroma.
Result:
Bilimbi was predominantly yellow to green and lighter in color compared to asam sunti which was predominantly yellow to red in color. Asam sunti has lower water content and higher ash content comparing to fresh bilimbi. QDA showed that green odor was significantly higher in bilimbi, while rancid odor and salty tastes were significantly higher in asam sunti. Umami attribute has also been detected in asam sunti. Maceration extraction produced the extract with the closest aroma to fresh samples of both bilimbi GC-O analysis revealed 22 odor active compounds in asam sunti. (E)-2-tetradecenal (OAV=49000), (E,Z)-2,4-decadienal (OAV=18428), nonanal (OAV=4850), pentadecanoic acid (OAV=3970), alpha-methyl ionone (OAV=1301), and (E)-2-octen-1-ol (OAV=1040) had high contributions to asam sunti aroma.
Conclusion
The physical, chemical and sensory characteristics of bilimbi and asam sunti were significantly different. The green odor intensity was dominant in bilimbi, while the rancid odor as well as salty and umami taste intensity were significantly higher in asam sunti. Analysis using GC-MS highlighted 83 volatile compounds. (E)-2-tetradecenal (OAV=49000), (E,Z)-2,4-decadienal (OAV=18428), nonanal (OAV=4850), pentadecanoic acid (OAV=3970), alpha-methyl ionone (OAV=1301), and (E)-2-octen-1-ol (OAV=1040) are proposed as aroma-active compounds of asam sunti.
Key words: aroma compounds, fermented bilimbi, asam sunti, OAV, traditional seasoning
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