Development of chitin nanofiber coatings for prolonging shelf life and inhibiting bacterial growth on fresh cucumbers.

The widespread usage of petroleum-based polymers as single-use packaging has had harmful effects on the environment. Herein, we developed sustainable chitin nanofiber (ChNF) coatings that prolong the shelf life of fresh cucumbers and delay the growth of pathogenic bacteria on their surfaces. ChNFs with varying degrees of acetylation were successfully prepared via deacetylation using NaOH with treatment times of 0-480 min and defibrillated using mechanical blending. With longer deacetylation reaction times, more acetamido groups (-NHCOCH3) in chitin molecules were converted to amino groups (-NH2), which imparted antibacterial properties to the ChNFs. The ChNF morphologies were affected by deacetylation reaction time. ChNFs deacetylated for 240 min had an average width of 9.0 nm and lengths of up to several µm, whereas rod-like structured ChNFs with a mean width of 7.3 nm and an average length of 222.3 nm were obtained with the reaction time of 480 min. Furthermore, we demonstrated a standalone ChNF coating to extend the shelf life of cucumbers. In comparison to the rod-like structured ChNFs, the 120 and 240-min deacetylated ChNFs exhibited a fibril-like structure, which considerably retarded the moisture loss of cucumbers and the growth rate of bacteria on their outer surfaces during storage. Cucumbers coated with these 120 and 240-min deacetylated ChNFs demonstrated a lower weight loss rate of ⁓ 3.9% day-1 compared to the uncoated cucumbers, which exhibited a weight loss rate of 4.6% day-1. This protective effect provided by these renewable ChNFs holds promising potential to reduce food waste and the use of petroleum-based packaging materials.

Garvieacin Q, a novel class II bacteriocin from Lactococcus garvieae BCC 43578.

Lactococcus garvieae BCC 43578 produces a novel class II bacteriocin, garvieacin Q (GarQ), 70 amino acids in length and containing a 20-amino-acid N-terminal leader peptide. It is cleaved at the Gly-Gly site to generate the mature GarQ (5,339 Da), which is especially inhibitory against Listeria monocytogenes ATCC 19115 and other L. garvieae strains.

Biogenic amine formation in Nham, a Thai fermented sausage, and the reduction by commercial starter culture, Lactobacillus plantarum BCC 9546.

Biogenic amines are of concern for sausage due to their toxicological effects on nervous, blood pressure, gastric and intestinal systems. In this study, the influence of raw pork meat quality and starter culture inoculation on biogenic amines accumulation in Nham, a Thai traditional fermented pork, were studied. Before Nham processing, pork meat was stored at 30°C for 6h, and at 4 and -20°C for 2days. Formation of biogenic amines (cadaverine, putrescine, histamine and tyramine) was significantly higher in Nham processed from stored meat. Accumulation of these biogenic amines in Nham reduced significantly by the addition of Lactobacillus plantarum BCC 9546, a commercial Nham starter culture. The results highlight the importance of using fresh meat products and the inclusion of an appropriate starter culture to minimise the formation of biogenic amines during the process of Nham fermentation.