Recent developments in preservation technologies allow for the delivery of food with nutritional value and superior taste. Of special interest are low-acid, shelf-stable foods in which the complete control or inactivation of bacterial endospores is the crucial step to ensure consumer safety. Relevant preservation methods can be classified into physicochemical or physical hurdles, and the latter can be subclassified into thermal and nonthermal processes. The underlying inactivation mechanisms for each of these physicochemical or physical processes impact different morphological or molecular structures essential for spore germination and integrity in the dormant state. This review provides an overview of distinct endospore defense mechanisms that affect emerging physical hurdles as well as which technologies address these mechanisms. The physical spore-inactivation technologies considered include thermal, dynamic, and isostatic high pressure and electromagnetic technologies, such as pulsed electric fields, UV light, cold atmospheric pressure plasma, and high- or low-energy electron beam.
Microalgal biomass is an emerging source of several health-related compounds, including polyunsaturated fatty acids. Herein, Chlorella vulgaris was cultivated heterotrophically in a 16-L stirred tank bioreactor. The lipid oxidative stability and lipid bioaccessibility of the biomass harvested during the exponential and stationary phases were evaluated. The biomass harvested during the stationary phase showed lower lipid oxidation than that harvested during the exponential phase, likely due to the higher content of antioxidants in the former. In both biomasses, the hexanal and propanal profiles showed only moderate increase over 12 weeks of storage at 40 °C, indicating good oxidative stability. Lipid bioaccessibility measured in an infant in vitro model was 0.66% ± 0.16% and 2.41% ± 0.61% for the biomass harvested during the exponential and late stationary phases, respectively. This study indicates that C. vulgaris biomass can be considered as a stable and nutritious (optimal ω3:ω6 profile) source of essential fatty acids. Our results suggested that regarding lipid stability and bioaccessibility, harvesting during stationary phase could be preferred choice. In general, treatment of the biomass to increase lipid bioaccessibility should be investigated.
Proteins from microalgae bear great potential to replace animal-based proteins in the human diet or as functional ingredients, such as interfacial stabilizers of emulsions and foams. To establish microalgae proteins as viable alternative, it is critical to understand the effect of physicochemical conditions on their adsorption behavior and interfacial network formation. Here, we extract a protein isolate from the cyanobacterium Arthrospira platensis and investigate its interfacial performance in a broad range of concentration, pH, ionic strength, and at oils with altering polarity. Compared to reference conditions (pH 7, 20 mM ionic strength) adsorption is accelerated at intermediate pH 5 due to decreased electrostatic repulsion but decelerated at the isolate's isoelectric point (pI = 3.5) due to protein aggregation. Conversely, a lower protein charge at the pI favors the formation of strong viscoelastic interfacial layers. Increased ionic charge screening results in faster adsorption and increased interfacial viscoelasticity. Adsorption at oils with varying polarity revealed that A. platensis isolate adsorption and viscoelasticity is largely independent of oil polarity and is only impeded at extremely polar oils. Based on this adsorption behavior, we conclude that the obtained isolate is a mixture of protein fractions with varying structural stability. Ultimately, we compare the interfacial performance of the A. platensis isolate with fractionated animal-based proteins. The A. platensis isolate is more efficient at reducing interface tension compared to the commonly employed β-lactoglobulin, lysozyme, albumin, or casein. Hence, A. platensis protein isolate is an efficient interfacial stabilizer in a broad range of physicochemical properties which outperforms many currently used animal-based proteins.
As the world population increases, food demand and agricultural activity will also increase. However, ~30–40% of the food produced today is lost or wasted along the production chain. Increasing food demands would only intensify the existing challenges associated with agri-food waste management. An innovative approach to recover the resources lost along the production chain and convert them into value-added product(s) would be beneficial. An alternative solution is the use of the larvae of the black soldier fly (BSFL), Hermetia illucens L., which can grow and convert a wide range of organic waste materials into insect biomass with use as animal feed, fertilizer and/or bioenergy. However, the main concern when creating an economically viable business is the variability in BSFL bioconversion and processing due to the variability of the substrate. Many factors, such as the nutritional composition of the substrate heavily impact BSFL development. Another concern is that substrates with high lignin and cellulose contents have demonstrated poor digestibility by BSFL. Studies suggest that pretreatment methods may improve the digestibility and biodegradability of the substrate by BSFL. However, a systematic review of existing pretreatment methods that could be used for enhancing the bioconversion of these wastes by BSFL is lacking. This paper provides a state-of-the-art review on the potential pretreatment methods that may improve the digestibility of substrates by BSFL and consequently the production of BSFL. These processes include but are not limited to, physical (e.g., mechanical and thermal), chemical (alkaline treatments), and biological (bacterial and fungal) treatments.
In this study the utility of insects as ingredients of organic diets for laying hens as a potential novel and more sustainable protein and energy source was investigated. The used insect material (protein meal and larval fat) was obtained from Black Soldier Fly (BSF) larvae reared on two permitted substrates (primarily grain-based agrifood sidestreams and preconsumer foodwaste, respectively) and then integrated in the diets of laying hens to completely replace soybean cake and oil. Over the feeding period of seven weeks various performance characteristics, protein and energy utilization, as well as egg quality were analyzed. The results show that replacement of soy meal and oil by insect materials did not negatively affect performance of the hens or the quality of the eggs. It remains to be investigated if and to which degree unfavorable saturated fatty acids, characteristic for BSF, are incorporated in the egg
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