What’s new and notable in bacterial spore killing!

Spores of many species of the orders Bacillales and Clostridiales can be vectors for food spoilage, human diseases and intoxications, and biological warfare. Many agents are used for spore killing, including moist heat in an autoclave, dry heat at elevated temperatures, UV radiation at 254 and more recently 222 and 400 nm, ionizing radiation of various types, high hydrostatic pressures and a host of chemical decontaminants. An alternative strategy is to trigger spore germination, as germinated spores are much easier to kill than the highly resistant dormant spores—the so called “germinate to eradicate” strategy. Factors important to consider in choosing methods for spore killing include the: (1) cost; (2) killing efficacy and kinetics; (3) ability to decontaminate large areas in buildings or outside; and (4) compatibility of killing regimens with the: (i) presence of people; (ii) food quality; (iii) presence of significant amounts of organic matter; and (iv) minimal damage to equipment in the decontamination zone. This review will summarize research on spore killing and point out some common flaws which can make results from spore killing research questionable.

Functionality of Cricket and Mealworm Hydrolysates Generated after Pretreatment of Meals with High Hydrostatic Pressures

The low consumer acceptance to entomophagy in Western society remains the strongest barrier of this practice, despite these numerous advantages. More positively, it was demonstrated that the attractiveness of edible insects can be enhanced by the use of insect ingredients. Currently, insect ingredients are mainly used as filler agents due to their poor functional properties. Nevertheless, new research on insect ingredient functionalities is emerging to overcome these issues. Recently, high hydrostatic pressure processing has been used to improve the functional properties of proteins. The study described here evaluates the functional properties of two commercial insect meals (Gryllodes sigillatus and Tenebrio molitor) and their respective hydrolysates generated by Alcalase®, conventionally and after pressurization pretreatment of the insect meals. Regardless of the insect species and treatments, water binding capacity, foaming and gelation properties did not improve after enzymatic hydrolysis. The low emulsion properties after enzymatic hydrolysis were due to rapid instability of emulsion. The pretreatment of mealworm meal with pressurization probably induced protein denaturation and aggregation phenomena which lowered the degree of hydrolysis. As expected, enzymatic digestion (with and without pressurization) increased the solubility, reaching values close to 100%. The pretreatment of mealworm meal with pressure further improved its solubility compared to control hydrolysate, while pressurization pretreatment decreased the solubility of cricket meal. These results may be related to the impact of pressurization on protein structure and therefore to the generation of different peptide compositions and profiles. The oil binding capacity also improved after enzymatic hydrolysis, but further for pressure-treated mealworm hydrolysate. Despite the moderate effect of pretreatment by high hydrostatic pressures, insect protein hydrolysates demonstrated interesting functional properties which could potentially facilitate their use in the food industry.

Formulation of a Tropical Beverage by Applying Heat Treatment and High Hydrostatic Pressure

Research background Passion fruit and carrot with vegetables that contain a good antioxidant capacity, however, their consumption is low. There is no information available on the use of these in beverages and with processes such as high hydrostatic pressures that allow the safety of the drink without affecting its quality. Experimental approach. In this study the effect of high hydrostatic pressures (HHP) (500 MPa, 250 s, 25 °C) and thermal processing (65 °C, 10 min; 75 °C, 2 min and 95 °C, 1 min) were evaluated, in the formulation of a cold pressed beverage composed of purple passion fruit, green passion fruit and carrot juice; Taking into account: antioxidant capacity, vitamin C content, sensorial evaluation and microbiological behavior at 8 °C. Results and conclusions. The formulation, 67 % purple passion fruit, 17 % green passion fruit and 17 % carrot was the one that stood out for its antioxidant capacity, high vitamin C content and sensorial evaluation. The HHP method preserved the antioxidant capacity and vitamin C, generated the best scent and showed no microbial growth during storage at 8 °C. Novelty and scientific contribution. In this study were used tropical raw materials that have good sensory acceptance and antioxidant capacity, which could be used in the generation of high value-added foods. Additionally, the research demonstrated that HHP is a conservation method that maintains the antioxidant capacity, vitamin C and aroma of the beverage to a greater extent compared to thermal treatments; the latter is of interest for its use in minimally processed products and functional food.

Formulation of a Tropical Beverage by Applying Heat Treatment and High Hydrostatic Pressure

Research background Passion fruit and carrot with vegetables that contain a good antioxidant capacity, however, their consumption is low. There is no information available on the use of these in beverages and with processes such as high hydrostatic pressures that allow the safety of the drink without affecting its quality. Experimental approach. In this study the effect of high hydrostatic pressures (HHP) (500 MPa, 250 s, 25 °C) and thermal processing (65 °C, 10 min; 75 °C, 2 min and 95 °C, 1 min) were evaluated, in the formulation of a cold pressed beverage composed of purple passion fruit, green passion fruit and carrot juice; Taking into account: antioxidant capacity, vitamin C content, sensorial evaluation and microbiological behavior at 8 °C. Results and conclusions. The formulation, 67 % purple passion fruit, 17 % green passion fruit and 17 % carrot was the one that stood out for its antioxidant capacity, high vitamin C content and sensorial evaluation. The HHP method preserved the antioxidant capacity and vitamin C, generated the best scent and showed no microbial growth during storage at 8 °C. Novelty and scientific contribution. In this study were used tropical raw materials that have good sensory acceptance and antioxidant capacity, which could be used in the generation of high value-added foods. Additionally, the research demonstrated that HHP is a conservation method that maintains the antioxidant capacity, vitamin C and aroma of the beverage to a greater extent compared to thermal treatments; the latter is of interest for its use in minimally processed products and functional food.

Buckling Analysis of an AUV Pressure Vessel with Sliding Stiffeners

The structure of an autonomous underwater vehicle (AUV), usually composed of a cylindrical shell, may be exposed to high hydrostatic pressures where buckling collapse occurs before yield stress failure. In conventional submarines, welded stiffeners increase the buckling resistance, however, in small AUVs, they reduce the inner space and cause residual stresses. This work presents an innovative concept for the structural design of an AUV, proposing the use of sliding stiffeners that are part of the structure used to accommodate the electronics inside it. Since the sliding stiffeners are not welded to the shell, there are no residual stresses due to welding, the AUV fabrication process is simplified, enabling a reduction of the manufacturing cost, and the inner space is available to accommodate the equipment needed for the AUV mission. Moreover, they provide a higher buckling resistance when compared to that of an unstiffened cylindrical shell. A comparative analysis of the critical buckling loads for different shell designs was carried out considering the following: (i) the unstiffened shell, (ii) the shell with ring stiffeners, and (iii) the shell with sliding stiffeners. Results evidenced that major advantages were obtained by using the latter alternative against buckling.