Utilization of areca nut (Arecha chatechu L.) extract for tannin based colorimetric indicator in smart packaging

Areca nut contains tannin which has a great potential to apply as natural colour agent in food industries. Tannin offers specific colour and alter its colour due to environmental sensitivity. This study aims to fabricate a tannin-based colour indicator from areca nut in smart packaging in the form of a strip type and to characterize the indicator at different storage conditions and at various pH solutions. The indicators were synthesized using filter paper (No.1 and No.42) soaked in a solution with 1, 3, and 5% areca nut ethanolic extract. Then the indicators were stored at room temperature and 4-7°C for 10 days, then their Red Green Blue (RGB) coefficient values were measured. Characterization of the indicators at pH 3-10 were also determined by RGB coefficient. The results showed that the indicator stored at 4-7°C had more stable RGB coefficient than the indicator stored at room temperature indicated the indicator was influenced by the temperature factor. The indicator offered a potential to be used as a sensor on packaging of temperature sensitive foods. The indicator using Whatman paper No.42 with 1% of extract steadily decreased in RGB coefficient and changed its colour to darker in basic pH solution while the indicator with other treatments had unstable alteration RGB coefficient and colour.

Characterization of tannin based colorimetric indicator and its application on fish packaging

This study aims to determine characteristics of the gel-type colorimetric indicator at various pH and under different storage conditions, then determine the indicator characteristic in the packaging of fish fillets during storage. The gel-type color indicator was synthesized with a concentration of 1%, 3%, and 5% gambir powder. The FT-IR spectra of the color indicator showed the presence of tannin functional groups, namely C=C aromatic rings, C-C phenolic, and C-H groups, respectively at wavenumbers 1517-1519, 1440-1475, and 752-761 1/cm. Moreover, the coefficient value of the Red-Green-Blue (RGB) of the indicator was changed over pH and did not appear to be consistent. Based on the Analysis of Variance (ANOVA) test, the concentration of gambir powder and duration of color indicator storage, respectively, had a significant effect (P <0.05) on the value of the RGB coefficient. The color indicator exposed to sunlight had a smaller RGB coefficient value than the RGB coefficient value of the indicator stored at room temperature and 5-7°C. The application of color indicators with a 1% Gambir powder concentration in fish fillet storage has been tested for 5 days at a temperature of 5-7°C. They showed that the RGB coefficient value of the indicator was proportional to changes in the pH value of fish fillets but not in line with changes in Total Volatile Based Nitrogen (TVBN) of fish fillets.

Two target genes based multiple cross displacement amplification combined with a lateral flow biosensor for the detection of Mycobacterium tuberculosis complex

Background Tuberculosis (TB) is a serious chronic infectious disease caused by Mycobacterium tuberculosis complex (MTBC). Hence, the development of a novel, simple, rapid and sensitive method to detect MTBC is of great significance for the prevention and treatment of TB. Results In this study, multiple cross displacement amplification (MCDA) combined with a nanoparticle-based lateral flow biosensor (LFB) was developed to simultaneously detect two target genes (IS6110 and mpb64) of MTBC (MCDA-LFB). One suite of specific MCDA primers designed for the IS6110 and mpb64 genes was validated using genomic DNA extracted from the reference strain H37Rv. The MCDA amplicons were analyzed using a real-time turbidimeter, colorimetric indicator (malachite green, MG) and LFBs. The optimal amplification temperature and time were confirmed, and the MCDA-LFB method established in the current report was evaluated by detecting various pathogens (i.e., reference strains, isolates and clinical sputum samples). The results showed that the two sets of MCDA primers targeting the IS6110 and mpb64 genes could effectively detect MTBC strains. The optimal reaction conditions for the MCDA assay were determined to be 67 °C for 35 min. The MCDA assay limit of detection (LoD) was 100 fg per reaction for pure genomic DNA. The specificity of the MCDA-LFB assay was 100%, and there were no cross-reactions for non-MTBC strains. For sputum samples and MTBC strain detection, the positive rate of MCDA-LFB for the detection of MTBC strains was consistent with seminested automatic real-time PCR (Xpert MTB/RIF) and higher than acid-fast staining (AFS) and culture assays when used for sputum samples. The MCDA-LFB assay was a rapid tool, and the whole procedure for MCDA-LFB, including DNA template preparation, MCDA reaction and amplification product analysis, was completed within 70 min. Conclusion The MCDA-LFB assay targeting the IS6110 and mpb64 genes is a simple, rapid, sensitive and reliable detection method, and it has potential significance for the prevention and treatment of TB.

Multicolor PEGDA/LCNF Hydrogel in the Presence of Red Cabbage Anthocyanin Extract

Colorimetric indicator gels were developed by incorporating anthocyanin (AC) obtained from red cabbage into poly (ethylene glycol) diacrylate (PEGDA)-based hydrogel containing lignocellulose nanofiber (LCNF). The PEGDA-based hydrogel was prepared by mixing all of the mentioned components at the specific composition, and the hydrogels were cured under UV light (245 nm) for 1 min. The pH-response, UV absorption, swelling ratio, and mechanical properties of PEGDA/LCNF were determined. It was further found that PEGDA and LCNF mount play an important role in adjusting the mechanical properties of PEGDA/LCNF. In general, the presence of LCNF improved the mechanical properties and swelling ratio of PEGDA. The incorporation of red cabbage anthocyanin into the PEGDA/LCNF film showed multicolor response when specific pH buffers were introduced. Based on the multicolor response of PEGDA/LCNF/CA, this gel film indicator can be developed as a food freshness indicator that focuses on the detection of ammonia and amine compound.