The probiotic Lactobacillus acidophilus KBL409 was encapsulated with alginate (Al) and alginate-chitosan (Al/Chi) through extrusion method. The sizes and zeta potentials of microspheres were measured to confirm encapsulation. To evaluate the protective effect of microspheres against gastrointestinal fluids, all the samples were exposed to simulated gastric fluids (SGFs, pH 1.5) at 37°C for 1 or 2 h, followed by incubation with simulated intestinal fluids (SIFs, pH 6.5) for 2 h. The mucoadhesive ability of microspheres was evaluated using the intestinal epithelial cell line HT29-MTX. To extend the shelf-life of probiotics, lyoprotectants such as disaccharide and polysaccharide were mixed with free or encapsulated cells during the freeze-drying process. The size of the microspheres demonstrated a narrow distribution, while the zeta potentials of Al and Al/Chi-microspheres were −17.9 ± 2.3 and 20.4 ± 2.6 mV, respectively. Among all the samples, Al/Chi-encapsulated cells showed the highest survival rate even after exposure to SGF and SIF. The mucoadhesive abilities of Al and Al/Chi-microspheres were higher than 94%, whereas the free L. acidophilus showed 88.1% mucoadhesion. Ten percent of sucrose showed over 80% survival rate in free or encapsulated cells. Therefore, L. acidophilus encapsulated with Al and Al/Chi-microspheres showed higher survival rates after exposure to the gastrointestinal tract and better mucoadhesive abilities than the free cells. Also, sucrose showed the highest protective effect of L. acidophilus during the freeze-drying process.

As storage temperature impacts frozen meat quality, we evaluated the ideal freezing and storage temperatures for pork loin, and effects of long-term storage at − 60, − 50, and − 18 °C on pork loin physicochemical properties. Pork loin was cut into 30 × 30 × 30 mm (50 g) and packed in air-containing box. Thereafter, they were stored at different freezing temperature for 6 months. Frozen pork loins were thawed at 4 °C. Samples frozen at − 18 °C exhibited surface dehydration (at 3 months) and high moisture loss surface dehydration-induced discoloration and toughening. However, samples frozen by deep freezing temperature (− 60 and − 50 °C) had lower values of thawing loss, WHC, and shear force than those of frozen at − 18 °C. Samples frozen at − 60 and − 50 °C maintained their freshness better than those frozen at − 18 °C; samples stored at − 60 °C showed significantly lower VBN than those stored at − 50 °C. Therefore, − 60 °C is suitable for freezing pork loins.

The effects of long-term deep freezing and standard storage temperatures on mackerel and croaker qualities were evaluated. Fishes were packed in aircontaining packages and stored at −60°C, −50°C, and −18°C for six months. Drip losses of the thawed deep-frozen fishes (−60°C) were lowest throughout the storage period (p< .05), whereas the WHC values were the highest (p<.05), and TBARS and TVBN levels were the lowest (p< .05). Consequently, these fishes were regarded as fresher than those stored at −50°C and −18°C, making this temperature desirable for maintaining mackerel and croaker quality during long-term storge.

No abstract