Effect of thermosonication on bioactive compounds, enzymatic and microbiological inactivation in nectar with strawberry by-products.

The aim of this study was to evaluate whether the addition of strawberry by-products (pulp and achene) and thermosonication offers a nectar with a potential contribution of health and safety benefits. Strawberry nectar with 0, 10 and 20% of strawberry by-products (SB) was subjected to thermosonication (24 kHz) at 70 and 80% for 8 min at 50 °C. Total soluble solids, pH, polyphenol oxidase (PO) and pectin methylesterase (PME) activities, total soluble phenols (TSP), ascorbic acid (AA), anthocyanins and antioxidant capacity (AOX) were evaluated. Microbiological reduction and inactivation of Escherichia coli was also determined. A limited activity was observed in PO and PME related to the SB percentage added. TSP, AA, anthocyanins, and AOX were increased due to the different percentages of SB added to the nectar. A reduction of aerobic mesophiles (1.28 Log CFU/mL), molds and yeast counts (1.23 Log CFU/mL) were achieved by thermosonication. E. coli inactivation was approximately 1 log CFU/mL in 20% SB nectar at 80% amplitude, 8 min at 50 °C, but increased during storage at 6 °C (0.915-5.86 Log CFU/mL). Thermosonication showed the possibility of employing strawberry by-products in nectars, improving the use of agro-industrial residues by non-thermal technologies.

Evaluation of Mycobacterium smegmatis as indicator of the efficacy of high hydrostatic pressure and ultra-high pressure homogenization treatments for pasteurization-like purposes in milk.

The objectives of this study were: to assess the efficiency of high hydrostatic pressure or ultra-high pressure homogenization against Mycobacterium smegmatis in milk and to discuss whether M. smegmatis can be considered a suitable surrogate for other Mycobacterium spp. in high pressure inactivation trials using milk. Three strains of this specie (CECT 3017, 3020 and 3032) were independently inoculated into both skimmed (0.2% fat) and whole milk (3.4% fat) at an approximate load of 6.5 Log CFU/ml and submitted to HHP treatments at 300, 400 or 500 MPa for 10 m at 6°C and 20°C. Evolution of the surviving cells of the inoculated strains was evaluated analysing milk immediately after the treatments and after 5 and 8 d of storage at 6°C. HHP treatments at 300 MPa were seldom efficient at inactivating M. smegmatis strains, but lethality increased with pressure applied in all cases. Generation of sub-lethal injured cells was observed only after 400 MPa treatments since inactivation at 500 MPa was shown to be complete. Significant differences were not observed due to either temperature of treatment or fat content of milk, except for strain CECT3032, which was shown to be the most sensitive to HHP treatments. Milk inoculated with strain CECT3017 was submitted to ultra-high pressure homogenization (UHPH) treatments at 200, 300 and 400 MPa. Maximum reductions were obtained after 300 and 400 MPa treatments, although less than 3.50 Log CFU/ml were inactivated. UHPH did not cause significant number of injured cells. The usefulness of this species as a marker for pressure-based processing seems limited since it showed greater sensitivity than some pathogenic species including other Mycobacteria reported in previous studies.

Gut metabolites produced during in vitro colonic fermentation of the indigestible fraction of a maize-based traditional Mexican fermented beverage, Tejuino.

Tejuino, is a Mexican fermented beverage prepared by germination-fermentation or nixtamalization-fermentation (artisanal and commercial mode respectively) of maize. The aim of this study was to evaluate the gut metabolites, volatile, and phenolic compounds (PC) produced by the indigestible fraction (IF) of Tejuino during an in vitro colonic fermentation. Twenty-six PC in the IF were identified; the hydroxycinnamic acids (30-40 %) were the most abundant. In the IF of Tejuino pyrogallol, and urolithins were identified. Some of the representative PC of maize as maysin derivatives (apimaysin and 3-methoxymaysin) (flavonoids). The quantification of acetic and butyric acid become notable after 6 h of the colonic fermentation of IF of Tejuino. Ninety-seven volatile compounds were found, and the PCA shows the predominant compounds as short chain fatty acids, esters of organic acids and indole derivatives. These results suggest that Tejuino could be an important source of metabolites with high biological value.