Curcumin and carvacrol mediated photodynamic inactivation with 405†nm light emitting diodes (LEDs) on Salmonella Enteritidis.

Photodynamic inactivation (PDI) has a potential application for food preservation that can minimize food pathogens posing risks to consumer health. This study aimed to evaluate the antibacterial activity of 405 nm light-emitting diodes (LEDs) illumination in the presence of carvacrol and curcumin against Salmonella Enteritidis and S. Enteritidis PT4 at different temperatures (4 °C, 25 °C and 37 °C) and time parameters (15 min, 30 min and 45 min) in the illumination system. Compared to their individual treatment, the decrease in the bacterial population was stronger in bacteria treated with LEDs + carvacrol or LEDs + curcumin. Co-application of carvacrol or curcumin with LEDs at 37 °C showed strong antibacterial activity against both bacteria depending on the application time. Co-application at 37 °C for 45 min completely inhibited the growth of S. Enteritidis. LEDs, curcumin, carvacrol applications alone or LEDs + curcumin, LEDs + carvacrol applications caused a decrease in bacterial population in proportion to the increase in the storage temperature and application times. These results showed that carvacrol or curcumin potentiates LEDs illumination therapy against both bacteria. Future studies on adapting the PDI system to control bacteria in a variety of foods may help develop novel strategies to fight against foodborne bacterial pathogens.

Effects of ambient conditions on solar assisted heat pump systems: a review.

Solar assisted heat pump (SAHP) systems aim to increase the performance of heat pumps by supporting with solar energy using various heating modes, whose performances depend on ambient conditions. In the literature, SAHP systems are classified by structure types, and the heating mode options are not considered as the main priority of the design but a result of the structure of the system. This paper aimed to investigate the effect of ambient conditions on heating modes, and identify the preferable ambient condition ranges for each SAHP system depends on their heating modes, by using a narrative review of 47 recent studies, that shed light on the problem. For this purpose, direct solar heating (DSH), air source heat pump (ASHP), solar source heat pump (SSHP) and solar-air source heat pump (S/ASHP) modes were stated as the basic heating modes of SAHP systems. In accordance with the literature, SAHP systems were classified as direct expansion solar assisted heat pump (DX-SAHP) and series, parallel and dual source indirect expansion solar assisted heat pumps (IDX-SAHP). Solar irradiation, ambient temperature, relative humidity and wind speed has been taken as major ambient conditions to investigate. Reviewed studies indicated that, parallel and series IDX-SAHP are preferable in high solar irradiations about 800 W/m2 with their DSH mode options. Frosting on evaporator is prevented in DX-SAHP with its S/ASHP mode, and even in the presence of frosting, unlike IDX-SAHPs ASHP mode, freezing is a factor that improves performance on flat evaporator in cold and humid conditions. This study indicates that there are obscure areas for future studies to focus on for a better comparison between SAHP types. Moreover, proposed novel designs of this paper, such as solar preheating of air in IDX-SAHP systems to add S/ASHP mode as an option, might enhance the performance and applicability of SAHP systems.