Physicochemical characteristics, microbial safety and biological activities of fermented black sesame (Sesamum indicum L.) seeds dregs
Utilization of dregs has been widely used, especially in Indonesia, such as peanut dregs into local Indonesian food known as “oncom”. Sesame seed dregs are derived from the process of making sesame oil. The seed dregs were then proceeded with spontaneous fermentation for 7 days at room temperatur...
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| Format: | Thesis |
| Language: | English |
| Published: |
2020
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/98235/1/FSTM%202021%2015%20-%20IR.pdf |
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| Summary: | Utilization of dregs has been widely used, especially in Indonesia, such as
peanut dregs into local Indonesian food known as “oncom”. Sesame seed dregs
are derived from the process of making sesame oil. The seed dregs were then
proceeded with spontaneous fermentation for 7 days at room temperature (23-
27°C). During fermentation, physicochemical characteristics of the food product
may undergo changes with microorganisms and bioactivities involvement in the
process. The aims of this study were to analyse physicochemical characteristics
and microbiological safety and quality of black sesame seed dregs during
fermentation, to determine antimicrobial and antioxidant activity, and to identify
bioactive compounds in raw black sesame seeds and fermented seed dregs
extract. Physicochemical characteristics including internal temperature, pH
value, total soluble solid (TSS), water activity (aw), colour determination,
proximate analysis and texture profile analysis of seed dregs during fermentation
were analysed using Association of Analytical Communities (AOAC) methods for
food analysis. The present of microorganisms including total plate count (TPC),
Escherichia coli, Salmonella spp., Pseudomonas aeruginosa, Bacillus cereus,
Staphylococcus aureus, lactic acid bacteria (LAB), coliform bacteria, mould and
yeast in seed dregs during fermentation were isolated using microbial selective
media. The collected samples for analysis were raw seeds and seed dregs at
day 0, 1, 3, 5 and 7 of fermentation. Raw seeds and fermented seed dregs (day
7) were extracted using water and ethanol and the extracts were further
determined for antimicrobial activity against foodborne pathogens using Clinical
and Laboratory Standard Institute (CLSI) methods. The total phenolic content
was determined using a Folin-Ciocalteu assay and antioxidant activity was
determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging
assay. The bioactive compounds in ethanol extract of raw seeds and fermented
seed dregs were determined using Gas Chromatography-Mass Spectrometry
(GC-MS) and Liquid Chromatography-Mass Spectrometry (LC-MS). The results
showed that internal temperature, pH and TSS showed no significant differences while aw shows the significant increased from 0.53 to 0.92% during fermentation.
The colour determination of final product had the highest lightness and
yellowness but had the lowest redness. Moisture was significantly increased
while ash, crude protein and carbohydrate were decreased and crude fat and
fibre were showed no significant differences during fermentation. A gradually
increased in hardness and decreased in springiness, chewiness and resilience
were observed while cohesiveness showed no significant differences. Microbial
counts were reduced in number of P. aeruginosa and B. cereus while increased
in number of TPC, S. aureus, lactic acid bacteria, coliform bacteria and mould
and yeast. The extraction yield using ethanol showed higher yield than water.
Diameter of inhibition zones of extracts against 16 pathogenic microorganisms
were in the ranged from 6.50 to 11.00 mm. Minimum inhibitory concentrations
(MICs) of water extract were in the range from 3.13 to >50.00 mg/mL, mostly
effective against B. cereus ATCC33019. Meanwhile, MICs of ethanol extract
were in the ranged from 6.25 to 50.00 mg/mL, mostly effective against P.
aeruginosa ATCC9027, B. megaterium ATCC14581 and C. albicans
ATCC10231. Minimum bactericidal/fungicidal concentrations of water and
ethanol were spread from 6.25 to >50.00 mg/mL and 25.00 to >50.00 mg/mL,
respectively. Time-kill curve study showed S. aureus ATCC29737, E. coli
ATCC43895 and B. cereus ATCC33019 were completely killed when exposed
to ethanol extract of raw seeds and fermented seed dregs in 0.5 h incubation at
4× MIC. One hour had been taken to completely killed P. aeruginosa ATCC9027
and Candida albicans ATCC10231 after exposing to raw seeds extract while two
hours had been taken after exposing to fermented seed dregs extract at 4× MIC.
The fermented seed dregs extract showed higher total phenolic contents rather
than raw seeds and seed dregs extracts. IC50 of the fermented seed dregs
extract showed lower concentration than raw seeds and seed dregs extracts.
There were 19 bioactive compounds in raw seeds and 24 compounds in
fermented seed dregs extract detected by GC-MS including sesamin and
sesamolin. Six compounds were identified to be the first time reported in sesame
seeds by LC-MS which were cyclo(L-leucyl-L-prolyl), docosahexaenoic acid
(DHA), enoxolone, α-eleostearic acid, 16-hydroxyhexadecanoic acid and
oleanolic acid. In conclusion, there were changes on physicochemical
characteristics during fermentation and fermented seed dregs had low level of
microbial counts, rich of lactic acid bacteria and detected bioactive compounds
were potentially good for antimicrobial and antioxidant activities. |
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