Harsi Dewantari Kusumaningrum

This study aims to design a high-efficiency Pulsed Electric Field (PEF) device for bacterial inactivation in food at a laboratory scale. Bacterial inactivation is closely affected by the consistency, intensity, and duration of the applied electric field; thus, although multiple circuit topologies can be employed in PEF devices, not all provide compactness and efficiency. For this study, an iterative design approach was used to evaluate solid-state cascade PEF topologies by comparing transformer-based (2 A and 5 A) and ignition coil-based (mini-cylinder, cylinder, and canister) configurations. The results show that PEF devices employing a 2 A transformer current and a mini-cylindrical ignition coil offer superior reliability and compactness, making them suitable for treating liquid, semi-solid, and solid samples. Experimental validation of the PEF effect on bacterial membrane damage, using the Vibrio parahaemolyticus strain, demonstrated that an electric field intensity of 10.5 kV/cm caused significant cell damage. Extended treatment durations led to progressively higher bacterial mortality (p < 0.05), as confirmed by flow cytometry and Scanning Electron Microscope (SEM) observations of cell morphology. Therefore, this study successfully developed a PEF device that potentially replaces the traditional Pulse Forming Network (PFN) with a mini-cylindrical ignition coil, thereby improving replicability and accessibility for laboratory-scale applications.

Pado adalah pangan fermentasi tradisional dari Provinsi Sumatra Barat, terbuat dari ikan pelagis yang dicampur dengan ampas kelapa dan cacahan daging biji picung (Pangium edulee) kering. Bakteri asam laktat merupakan bakteri yang dominan ditemukan pada produk fermentasi dan umumnya dapat mensekresikan metabolit yang berperan dalam membantu memperpanjang masa simpan produk pangan. Supernatan bebas sel yang dinetralkan (NCFS) dari isolat tersebut diduga mengandung peptida bioaktif, yaitu peptida antibakteri. Penelitian ini bertujuan untuk menentukan NCFS murni parsial yang dihasilkan oleh isolat asal pado dengan aktivitas penghambatan terbaik terhadap Salmonella Typhimurium dan Staphylococcus aureus menggunakan metode agar difusi. NCFS kasar diperoleh dari tujuh isolat pado dengan sentrifugasi media pertumbuhannya dan menetralkan supernatannya. Sifat protein dari NCFS kasar dikonfirmasi dengan memaparkan enzim pepsin proteolitik. Ultrafiltrasi digunakan untuk memurnikan NCFS kasar secara parsial. Peptida antibakterinya dikarakterisasi menggunakan liquid chromatography-high resolution mass spectrometry (LC-HRMS). Semua NCFS menunjukkan aktivitas antibakteri terhadap S. Typhimurium, tetapi hanya tiga isolat yang menunjukkan aktivitas penghambatan terhadap S. aureus. Isolat Lactiplantibacillus plantarum B3Iw4 dipilih untuk penelitian lanjut. Fraksi NCFS dengan berat molekul rendah (dalam rentang 317,20 Da hingga 1.494,70688 Da) setelah ultrafiltrasi dengan membran 3 kDa menunjukkan peningkatan aktivitas spesifik tiga kali lipat terhadap S. aureus dibandingkan dengan NCFS kasar. Analisis LC-HRMS mengidentifikasi 20 peptida dalam NCFS murni parsial. Satu peptida, AAERAGAAALAMHGR, diprediksi memiliki aktivitas antibakteri setelah dicocokkan dengan basis data BIOPEP-UWM, dengan sekuen yang cocok AA. Peptida ini memiliki sifat hidrofobisitas yang relatif tinggi dan menarik untuk diteliti lebih lanjut.

Squid are susceptible to bacterial contamination by Vibrio parahaemolyticus, with a prevalence of 80%. Squid preservation is generally achieved by drying after brine salting, which does not always completely stop the growth of V. parahaemolyticus. To reduce bacterial numbers, a boiling process is usually conducted before drying. This study aimed to determine the optimal electric field and duration for inactivating V. parahaemolyticus and evaluating the effectiveness of pulsed electric fields (PEF) technology on salted squid. PEF technology specifications with a current strength of 2 amperes using electric fields (3.5, 7, and 10.5 kV/cm) and time durations (10, 20, and 30 s). Bacterial reduction by electric fields was observed using colony counts, followed by counting of dead cells using a flow cytometer. Bacterial damage was observed using a scanning electron microscope. The results showed that PEF with the highest intensity (10.5 kV/cm for 30 s) reduced V. parahaemolyticus by 66.12% at high contamination levels (approximately 106 CFU/g) and 97.63% at low contamination levels (approximately 102 CFU/g) in salted squid. These results were comparable to those obtained after boiling treatment (2 min, 85°C). Damage to the bacterial cell membrane increased due to the increasing electric field, as observed by increasing in red fluorescing cells by flow cytometry and cell damage by SEM. PEF is a promising alternative technology for producing salted squid.

Different species of marine macroalgae have been reported to demonstrate antimicrobial activities against numerous bacteria, with varying results. According to the studies, other antibiotics have been used as positive controls. This study evaluated the effect of crude extracts and sulphated polysaccharides from Chlorophyta, Phaeophyta, and Rhodophyta in inhibiting bacterial growth in terms of the diameter of inhibition zones (DIZ) using a systematic review and meta-analysis approach. A total of 835 data, extracted from 23 selected articles, were analyzed using OpenMeesoftware by comparing the standardized mean difference (SMD) and 95% confidence interval (CI). The largest DIZ that Chlorophyta showed was 35 mm, Phaeophyta was 27.3 mm, and Rhodophyta was 25.66 mm, which was categorized as a very strong activity. The crude extract revealed a better inhibitory activity than the sulphatedpolysaccharides. The overall effect size for crude extracts was with SMD = -1.72 (CI = -1.96 to -1.48, I2 = 84.65%, p 0.000) and for sulphated polysaccharides with SMD = -13.07 (CI = -16.00 to -10.14, I2 = 85.8%, p 0.000), respectively. Subgroup analysis showed that when ciprofloxacin was used, the SMD value was -12.88 (CI = -14.50 to -11.25), whereas if ampicillin was used, the SMD value was 1.81 (CI = 1.27 to 2.35). This study proved that Chlorophyta, Phaeophyta, and Rhodophyta revealed promising antibacterial activities. However, the overall effect size was affectedby the antibiotic used when comparing the SMD of the DIZ using a meta-analysis approach. Other factors, such as extraction methods and bacterial strains that likely affect the overall effect size, are subjected to further analysis in the next study.

Terasi is a traditional fermented product that is popularly used as condiment in several Indonesian cuisines. Based on its raw materials, namely shrimp and marine fish, terasi provides a substrate for various protease-producing microorganisms. This study aimed to isolate protease-producing bacteria from terasi and to assess their crude enzyme as meat tenderizer. Seven terasi samples from different regions were used as sources for proteolytic bacteria. They were inoculated on skim milk agar media, on which 137 isolates were found with 1-2 cm clear zones and 41 isolates with more than 2 cm clear zones, implying their proteolytic activity. Most of the isolates were Gram-positive bacteria. The crude enzymes from twenty selected isolates were assessed for meat tenderization, by dipping the meat cut into solution of crude proteolytic enzymes. Measurement of the shear force value (SFV) of meat treated with crude enzymes from 20 isolates showed that 14 of the 20 treatments had lower SFV (21.52 to 34.12 g/cm²) than the control (34.77 g/cm²). The three isolates that showed the best meat tenderizing activity were isolates Tr18, Tr13 and Tr4 with SFV 21.52 g/cm², 21.54 g/cm², and 25.77g/cm², respectively. These isolates are interesting to be used in the future study for further characterization.

The plant of Metroxylon sago Rottb. which is found abundantly in Indonesia, Malaysia, Philippines, and Papua New Guinea, is famous as carbohydrate producing plants. The sago fruit has not been yet extensively used, although they are rich in oligosaccharides which is potential as prebiotic. Sago fruit flour was studied as growth substrate for five selected probiotics and phytochemical profile of its methanol extracts were determined. All bacteria grew well up to 24 h on the growth medium containing sago fruit flour as carbohydrate substitute. However, Lacticaseibacillus rhamnosus FNCC 0099 and Lactobacillus acidophilus FNCC 0051 showed viability stability up to 72 h, while the others were slightly decreased. The sago fruit flour contained 20.4 mg/g total sugars, 14.8 mg QE/g flavonoids, and 36.7 mg GAE/g phenolics. After extraction of the fruit flour with 80% methanol using an ultrasonicator at 55 °C at 40 kHz for 40 min, the extract was analysed for its phytochemical profiles using untargeted LC-MS/MS screening with negative ionization mode. Seven compounds categorised in three distinct groups i.e., sugar alcohol, plant glycosides and fatty acids, have been identified as having possible prebiotic activity. These include ((1xi)-1,5-anhydro-2,3,6-tris-O-(carboxymethyl)-1-methyl-4-O-methyl-D-glucitol), quercitrin, (15Z)-9,12,13-trihydroxy-15-octadecenoic acid, corchorifatty acid F, 3,5-dihydroxy-2-(4-hydroxyphenyl)-4-oxo-3,4-dihydro-2H-chromen-7-yl-hexopyranoside, gynocardin, and (4-methylumbelliferone)-b-D-glucopyranoside. As the sago fruit flour has been proved as potential prebiotic in this study, its extensive prebiotics activity, prebiotic index, and stability under digestive condition will be subjected for further study.

Noni (Morinda citrifolia) is a popular plant in Asian countries and has great potential as pectin source for thickening agents in food products. In general, ethanol has been widely used to precipitate pectin, but the proportion can affect the quality of the product. Therefore, this study aimed to characterize the physicochemical properties of pectin from noni fruit. Extraction was performed using 0.1 N HCl at pH 1.5 and heated at 80°C for 15 min, followed by precipitation with different proportions of 96% ethanol including A (1:1), B (1:2), and C (1:3) v/v, while commercial orange pectin was used as a reference. The results showed that all pectin extracted belonged to the high methoxyl category. The FTIR spectra confirmed the presence of important functional groups including OH-hydroxyl, CH3-saturated aliphatic methyl, C=O carbonyl, and -O- cyclic ether. Furthermore, the crystalline and amorphous structures of noni pectin were confirmed by X-ray diffraction observation. The highest yield was achieved using the proportion of 1:3, followed by 1:2, and 1:1 on a wet basis. The MeO and AUA content of sample B (1:2) were relatively similar to those of the reference. Based on extraction results, noni possesses good characteristics and has the potential for commercial pectin production.

This study investigated the effect of commercial sterilisation treatment (121 °C for 15 min) on durian rind pectin. The change of structure was observed by NMR (nuclear magnetic resonance) and the antibacterial activity was assessed by microdilution method to obtain the minimum inhibitory concentration (MIC) value. NMR spectra revealed the rhamnogalacturonan-I and homogalacturonan structure, with lower methyl-ester in sterilised pectin. Native pectin was unable to inhibit Escherichia coli and Staphylococcus aureus at the highest tested concentration (MIC > 25 mg/mL), but sterilised pectin showed inhibitory effect against E.coli (MIC 12.5 mg/mL) and S. aureus (MIC 6.25 mg/mL). Membrane filtration to obtain fraction < 20 kDa enhanced the inhibition against S. aureus further, but not for E.coli. The antibacterial effect was possibly correlated to the decrease of molecular weight (MW) and degree of esterification (DE) of durian rind pectin. E. coli was more resistant to pectin than S. aureus.

Summary: Bacteriocins are antimicrobial peptides synthesised ribosomally by bacteria that can be used as natural preservatives. One potential bacteriocin‐producing bacteria that has yet to be widely studied is Streptomyces sp. Bioinformatics analysis has been conducted on the purified and identified bacteriocin‐like inhibitory substances (BLIS) produced by Streptomyces sp. The BLIS fraction, purified by reversed‐phase high‐performance liquid chromatography, showed significantly increased specific activities against E. coli, L. monocytogenes, S. aureus and S. typhimurium (1.2–189.4 folds). Identification of four purified BLIS fractions using HR‐LC‐ESI‐MS/MS revealed molecular mass from 1287.51 to 1812.85 Da with the sequences of TAEAEAAEGAEEAAP (fraction AS531), TQGGINANKTGSQGYG (fraction AS822), SGGYGGMGAGGIGGQRSGPQ (fraction AS857) and PGGAKGGFGGGGRPGGQGMPGG (fraction AS1121). These peptide sequences have a minimum of 2 hydrophobic amino acids, a net charge of −4 to +2, an isoelectric point of 2.68–11.71 and a hydrophobicity of 20.44–27.46 kcal mol⁻¹. The results of molecular docking analysis between purified BLIS and the penicillin‐binding protein 3 (PBP‐3) receptor by methicillin‐resistant Staphylococcus aureus (MRSA) also showed that four fractions had low binding energy (−7.5 to −8.1 kcal mol⁻¹) with 17–25 hydrogen bonds and distances in vitro characterisation revealed that the four purified‐BLIS have a low to moderate LC₅₀ (68.81–200.35 μgmL⁻¹) against A. salina and the ability to maintain 50% antibacterial activity against E. coli up to 100 °C for 30 min and in the pH range of 2.0–8.0, especially fractions AS531 and AS822. Based on the antibacterial spectrum, physicochemical characteristics and peptide sequence, BLIS produced by Streptomyces sp., is a novel bacteriocin with promising applications as a food preservative.

The online food delivery (OFD) is known to be a fast-growing business in Indonesia, with the largest platforms, namely GoFood and GrabFood. Hence, the level of knowledge and awareness of the stakeholders, including restaurants, delivery partners, and customers on the safety of the ready-to-eat food is important to ensure that the delivery does not rise a potential health hazard. This study aimed to determine the factors affecting the delivery process of ready-to-eat food, via the OFD system, in terms of educational backgrounds, experience, implementation of regulations, as well as knowledge and awareness of safety among the stakeholders. The research location was Depok, a growing city nearby Jakarta, which is known to support the growth of OFD, with a relatively dense population, sufficient internet network, educational level, and employed individuals. The survey was conducted in regard to hot soup and fried/grilled food restaurants, delivery partners, and customers that are members of GoFood and GrabFood, with 110 respondents from each group. The results presented an overview of the OFD system during the COVID-19 pandemic since it was conducted between December 2020 to March 2021. The food safety knowledge profile of the stakeholders in regard to OFD was relatively good. This knowledge was not significantly affected by educational background, experience, training, or practical monitoring. However, their food safety awareness still needs to be improved. It is further suggested that the visitation frequency to restaurants by the local health authority should be increased, the hygiene monitoring team should be reporting via application, regular inspection by the delivery partners, and organizing food safety campaigns for the customers. This study also showed that there are significant differences between food safety knowledge and awareness among the stakeholders. This condition should be mitigated by improving safety awareness, during the process of OFD, involving continuous training delivery partners, consistent visitation of the OFD provider, the improvement of system and facilities, provision of a special container, and promoting the usage.