The worldwide growing consumption of proteins to feed humans and animals has drawn a considerable amount of attention to insect rearing. Insects reared on organic wastes and used as feed for monogastric animals can reduce the environmental impact and increase the sustainability of meat/fish production. In this study, we designed an environmentally closed loop for food supply in which fruit and vegetable waste from markets became rearing substrate for Hermetia illucens (BSF— black soldier fly). A vegetable and fruit-based substrate was compared to a standard diet for Diptera in terms of larval growth, waste reduction index, and overall substrate degradation. Morphological analysis of insect organs was carried out to obtain indications about insect health. Processing steps such as drying and oil extraction from BSF were investigated. Nutritional and microbiological analyses confirmed the good quality of insects and meal. The meal was then used to produce fish feed and its suitability to this purpose was assessed using trout. Earthworms were grown on leftovers of BSF rearing in comparison to a standard substrate. Chemical analyses of vermicompost were performed. The present research demonstrates that insects can be used to reduce organic waste, increasing at the same time the sustainability of aquaculture and creating interesting by-products through the linked bio-system establishment.
The aim of this work was to develop processing methods that safeguard the quality and antimicrobial properties of H. illucens and B. mori oils. We adopted a vegetable diet for both insects: leftover vegetables and fruit for H. illucens and mulberry leaves for B. mori. First, alternative techniques to obtain a good oil extraction yield from the dried biomass of H. illucens larvae were tested. Traditional pressing resulted to be the best system to maximize the oil yield and it was successfully applied to B. mori pupae. Oil quality resulted comparable to that obtained with other extraction methods described in the literature. In the case of B. mori pupae, different treatments and preservation periods were investigated to evaluate their influence on the oil composition and quality. Interestingly, agar diffusion assays demonstrated the sensitivity of Gram-positive Bacillus subtilis and Staphylococcus aureus to H. illucens and B. mori derived oils, whereas the growth of Gram-negative Pseudomonas aeruginosa and Escherichia coli was not affected. This study confirms that fat and other active compounds of the oil extracted by hot pressing could represent effective antimicrobials against bacteria, a relevant result if we consider that they are by-products of the protein extraction process in the feed industry.
To study the storage stability of drinks produced by blending ricotta cheese whey (RCW) with fruit juices, apple-RCW and apple and blueberry mix (50:50)-RCW (juice/RCW ratio: 70/30, 14.5% soluble solids content) were prepared. Color, sugar and organic acid profiles, antioxidant composition, and sensory features were analyzed after 15 to 150 days of storage on an open shelf at room temperature. A browning phenomenon occurred in the apple-RCW-based drink, while no significant color changes occurred in the mix-based drink. Significant degradation of polyphenol compounds (TPC) occurred in both drinks, but more markedly in the mix-based one. Storage strongly influenced the stability of the total monomeric anthocyanins (MAP) due to their sensitivity to temperature and light. Antioxidant capacity was preserved in both drinks, suggesting that the antioxidant capacity of Maillard reaction products and/or polymeric anthocyanins formed during storage compensated for the TPC/MAP loss. Sugar and organic acid profiles changed without influencing the sensory characteristics. Except for the sourness intensity in the apple-based drink, which increased significantly, storage did not negatively influence the sensory parameters, so both RCW-based drinks obtained high acceptance scores at the end of the storage period. Despite the bioactive compound losses, both drinks provided interesting nutritional value at the end of the storage period, particularly the mix-based drink. The overall results showed that both products are stable enough to hypothesize their commercialization.
Air-dried apple rings were prepared from ‘Golden Delicious’ apples selected at harvest as less mature and more mature according to the absorption coefficient measured at 670 nm by time-resolved reflectance spectroscopy (TRS), stored in air for 5 months, and subjected to air-drying with (OSMO) and without (noOSMO) osmodehydration pre-treatment (60% sucrose syrup). Selected rings were submitted to microstructural analysis by X-ray computed tomography (X-CT), to subsurface structure analysis by optical coherence tomography (OCT) and to texture and sound emission analysis by bending–snapping test. Higher crispness index, higher number of sound events and higher average sound pressure level (SPL) characterized the OSMO rings. Total porosity was related to SPLav < 60, tissue and pore anisotropy to SPLav > 60, pore fragmentation index to fracturability and specific surface area to the work required to snap the ring. A differentiation of the drying treatments, as well as of the products according to the TRS maturity class at harvest was obtained analyzing by principal component analysis (PCA) microstructure parameters and texture and acoustic parameters. The differences in mechanical and acoustic characteristics between OSMO and noOSMO rings were due to the different subsurface structure as found with OCT analysis
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