No abstract

Beta-carotene is a carotenoid with a wide spectrum of biological activities (e.g., anti-cancer, anti-hypertensive, and anti-inflammatory). However, because of its extremely high hydrophobicity, it is difficult to incorporate in food formulations and its bioavailability is fairly low. Lipid-based encapsulation colloidal systems such as lipid nanoparticles can help overcome these issues. In this study, beta-caroteneloaded lipid nanoparticles were produced by the phase inversion temperature (PIT) method from 10% cupuacu butter and 20% surfactant (Cremophor RH40 and Span 80). The inversion temperature of the nanoparticles was 74 C and their average diameter was 35 nm. After 100 days of storage, 85% of the initial amount of beta-carotene remained in the nanoparticles; alpha-tocopherol was found to be essential for carotenoid preservation. Comparison of the results of in vitro digestion between static and dynamic systems was performed, and the characteristics of each digestion system led to diverse results in terms of average particle size and beta-carotene bioaccessibility. Although the static system was much simpler than the dynamic system, it could not provide reliable data of the digestibility of the lipid nanoparticles. The bioaccessibility of beta-carotene in the static system was 92%, very similar to the results found in the literature; by comparison, the dynamic system revealed a beta-carotene bioaccessibility of nearly 20%. Despite this discrepancy, the highly realistic conditions of digestion simulated by the dynamic in vitro system indicate that the results of this system are more reliable than those obtained from the simplified static system applied in this research.

Postprocessing cross-contamination of cheese can lead to both food safety issues and significant losses due to spoilage. Pulsed light (PL) treatment, consisting of short, high-energy, broad-spectrum light pulses, has been proven effective in reducing the microbial load on cheese surface. As PL treatment effectiveness is limited by light-cheese interactions, the possibility to improve its effectiveness by combining it with the antimicrobial nisin was explored. The effect of natamycin, which is added to cheeses as an antifungal agent, on PL effectiveness was also investigated. Pseudomonas fluorescens, Escherichia coli ATCC 25922, and Listeria innocua were used as challenge microorganisms. Bacterial cultures in stationary growth phase were diluted to initial inoculum levels of 5 or 7 log cfu per cheese slice. Slices of sharp white Cheddar cheese and white American singles were cut in rectangles of 2.5 × 5 cm. For cheese slices receiving antimicrobial treatment before PL, slices were dipped in natamycin or nisin, spot inoculated with 100 μL of bacterial suspension, and then treated with PL. Cheese slices receiving PL treatment before antimicrobials were spot inoculated, treated with PL, and then treated with antimicrobials. The PL fluence levels from 1.02 to 12.29 J/cm were used. Survivors were enumerated by standard plate counting or the most probable number technique, as appropriate. All treatments were performed in triplicate, and the data were analyzed using a general linear model. Treatment with nisin or natamycin before PL decreased the effectiveness of PL for all bacteria tested. For instance, PL reduced P. fluorescens on Cheddar cheese by 2.19 ± 0.27 log after 6.14 J/cm, whereas combination treatments at the same PL fluence yielded barely 1 log reduction. Inactivation of L. innocua on Cheddar was only 0.78 ± 0.01 log when using PL after nisin, compared with a 1.30 ± 0.76 log reduction by nisin alone. This was attributed to the absorption of UV light by the 2 antimicrobials, which diminished the UV fluence received by the bacteria. Increased inactivation was obtained when antimicrobials were applied after PL. On process cheese, a maximum reduction of 3.73 ± 0.96 log of L. innocua was obtained at 9.22 J/cm for PL followed by nisin, compared with 3.01 ± 0.48 by PL alone. This study demonstrates that antimicrobials may increase the antimicrobial effectiveness of PL on cheese surface, but the order of treatments is critical.