Identification, proteolytic activity quantification and biofilm-forming characterization of Gram-positive, proteolytic, psychrotrophic bacteria isolated from cold raw milk

Psychrotrophic bacteria of raw milk face the dairy industry with significant spoilage and technological problems due to their ability to produce heat-resistant enzymes and biofilms. Despite extensive information about Gram-negative psychrotrophic bacteria in milk, little is known about Gram-positive psychrotrophic bacteria in milk, and their proteolytic activity and biofilm-forming characteristics. In the present study, Gram-positive, proteolytic, psychrotrophic bacteria of cold raw milk were identified, and their proteolytic activity and biofilm-forming capacity were quantified. In total, 12 genera and 22 species were represented among the bacterial isolates, however 50% belonged to three genera, namely Staphylococcus (19.4%), Bacillus (16.7%), and Enterococcus (13.9%). Different levels of proteolytic activity were detected in the identified isolates, even among the strains belonging to the same species. In addition, proteolytic activity was significantly higher at 25°C than at 7°C for all isolates. The crystal violet staining assay in polystyrene microtitre plates revealed a high level of variation in the biofilm-forming capacity at 7°C. After 72 hours of incubation, 11.1% of the strains did not produce a biofilm, while 27.8%, 52.8%, and 8.3% produced low, moderate, and high amounts of biofilm on polystyrene, respectively. The psychrotrophic bacteria were also able to produce biofilms on the surface of stainless steel coupons in ultra-high temperature milk after 72 h of incubation at 7°C; the number of attached cells ranged from 1.34 to 5.11 log cfu/cm2. These results expand the knowledge related to the proteolytic activity and biofilm-forming capacity of Gram-positive psychrotrophic milk bacteria.

Child temperament is associated with energy intake and its day-to-day variability among preschoolers-Results from a cross-sectional DAGIS study

BACKGROUND

Although research has linked children's temperament with weight outcomes, the associations between temperament and dietary outcomes, particularly energy intake, remain understudied. Furthermore, little is known about how temperament is associated with diet in the early childhood education and care (ECEC) context, which is an important environment for many children.

OBJECTIVES

This study examined whether temperament is associated with mean energy intake and its day-to-day variability. In addition, the associations were examined separately in the contexts of home and ECEC.

METHODS

The study used data from 505 Finnish children from a cross-sectional DAGIS study conducted in 2015-2016. Parents reported their child's temperament with a questionnaire and food consumption with a food record for two weekdays (outside daycare hours) and one weekend day. Early educators at an ECEC centre reported the child's food consumption during the daycare hours on the same weekdays as the parents kept food records at home. Associations were examined with linear regression models.

RESULTS

Children with higher surgency had a higher mean daily energy intake. When examined separately at home and in the ECEC centre, the association was found only in the ECEC centre. Children with higher negative affectivity had greater day-to-day variability in energy intake. This association, however, was not observed when examined separately at home and at the ECEC centre.

CONCLUSIONS

The results indicate that temperament may shape children's energy intake. Moreover, the role of the ECEC context in children's eating may be different depending on a child's temperamental dispositions, which warrants further research.