The effect of gamma irradiation on microbial load of purple basil ( Ocimum bacilicum L.) leaves dried in different methods

Postharvest Microwave Drying of Basil (Ocimum basilicum L.): The Influence of Treatments on the Quality of Dried Products

Edible herbs are widely used in the human diet due to their pleasant flavors and countless health benefits associated with their components having, mainly, antioxidant and anti-inflammatory therapeutic functions. Since herbs are highly perishable materials because of their high water content, to guarantee products are safe and stable over time, it is necessary that they undergo stabilization operations. The application of microwave-assisted drying, a promising technique in terms of process sustainability, for the stabilization of the aromatic herb, Ocimum basilicum L., was investigated. The activities were carried out by applying different operating conditions in order to evaluate the impact of the time/temperature combination on the final quality of dried basil. The latter was investigated via the chemical characterization of extracted essential oils and tissue damages. Conventional convective processes were also applied to perform comparisons between dried basil products both under production and the quality preservation points of view. Results showed that microwave heating is suitable as a drying method, as expected, due to the well-known interaction between vegetable tissue (rich in water) and the electromagnetic field; and that drying methods have a different influence on the chemical composition of the essential oils extracted from dried products, in terms of the number (ranging from 41 to 18 components in different dried samples) and percentage (until 67% in linalool and 21% in α-trans-bergamotene in different dried samples) of its' constituents.

Zn, Cu, and Fe Concentrations in Dehydrated Herbs (Thyme, Rosemary, Cloves, Oregano, and Basil) and the Correlation with the Microbial Counts of Listeria monocytogenes and Other Foodborne Pathogens

Zn, Cu, and Fe concentrations were measured in dehydrated herbs (thyme, rosemary, cloves, oregano, and basil) marketed in bulk or packaged in glass or polyethylene terephthalate (PET). Microbial counts of Listeria monocytogenes and other five foodborne pathogens were also checked when herbs were previously added to the growing media. The highest mean concentrations were found in basil for Zn and Cu, and in thyme and basil for Fe; the lowest ones for these minerals were in cloves (p < 0.05). Basil had significantly higher microbial counts in five of the six foodborne pathogens studied (p < 0.05). Cloves have the best hygienic quality as there is no microbial growth of L. monocytogenes, Clostridium perfringens, and Bacillus cereus; they therefore could be used as a natural preservative in food. Aromatic herbs marketed in bulk showed a significantly higher microbial count (p < 0.05). Zn, Cu, and Fe concentrations were positively correlated with microbial growth for L. monocytogenes, C. perfringens, B. cereus, and psychrophilic microorganisms (p < 0.05), so they could act as a growing factor for the foodborne pathogens.

Effects of X-ray irradiation on the postharvest quality characteristics of 'Maehyang' strawberry (Fragaria × ananassa)

This study evaluated the effects of X-ray irradiation (0-1 kGy) on quality parameters of Korean strawberries during storage at 15 °C for 9 d. As compared to control, all irradiated samples exhibited dose-dependent decreases in microbial counts regardless of storage period. Irradiation significantly (p < 0.05) reduced weight loss and decay incidence of fruits during storage. Fruit firmness decreased immediately after irradiation, but no significant changes occurred after 3 d. Neither irradiation nor storage period significantly affected total soluble solids, pH, or titratable acidity. All treatments delayed color changes and pelargonidin accumulation during storage. The radical scavenging activities and total phenolic, ellagic acid, and catechin contents increased gradually during storage. Furthermore, irradiated fruits showed improved sensory characteristics throughout storage. Thus, X-ray irradiation (≤1 kGy) was confirmed as a effective phytosanitary treatment for strawberries to delay decay and negative physicochemical changes and extend shelf life with acceptable sensory attributes.

Encapsulated Bdellovibrio Powder as a Potential Bio-Disinfectant against Whiteleg Shrimp-Pathogenic Vibrios

Liquid preparations of bdellovibrios are currently commercialized as water quality improvers to control bacterial pathogens in whiteleg shrimp Penaeus vannamei. However, the efficacy of these liquid preparations is significantly impaired due to a dramatic loss of viable cells during long-term room temperature storage. Thus, new formulations of bdellovibrios are greatly needed for high-stablility room-temperature storage. In the present study, the encapsulated powder of Bdellovibrio sp. strain F16 was prepared using spray drying with 20 g L-1 gelatin as the coating material under a spray flow of 750 L h-1, a feed rate of 12 mL min-1, and an air inlet temperature of 140 °C. It was found to have a cell density of 5.4 × 107 PFU g-1 and to have spherical microparticles with a wrinkled surface and a diameter of 3 μm to 12 μm. In addition, the encapsulated Bdellovibrio powder presented good storage stability with its cell density still remaining at 3.5 × 107 PFU g-1 after 120 days of room-temperature storage; it was safe for freshwater-farmed whiteleg shrimp with an LD50 over 1200 mg L-1, and it exhibited significant antibacterial and protective effects at 0.8 mg L-1 against shrimp-pathogenic vibrios. To our knowledge, this is the first report on a promising Bdellovibrio powder against shrimp vibrios with high stable room-temperature storage.