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The study of primary plant metabolism has been the main focus of scientists for several years, seconding research related to the secondary metabolism. Nowadays, with the better understanding of the processes and products involved in primary metabolism, the focus has switched to the expansion of knowledge involving secondary metabolism. Initially, plants were the focus of secondary metabolite studies due to their ease of acquisition and availability, reasons for being a term coined by plant physiologists. Only in the twentieth century has the secondary metabolites from microorganisms began to be recognized and investigated due to the value that these metabolites could bring to science. Not by chance, it was in the twentieth century that the era of antibiotics began. In this chapter, a voyage through the centuries is proposed, focused on secondary metabolism and metabolites, highlighting how they shifted from disregarded molecules to the powerhouses of bioactivity for modern science.

Food waste is one of the fundamental issues when it comes to environmental impacts, and this type of waste results in the food’s loss itself, but also that of water, energy, fertilizers, and other resources used for its production. Many vegetable parts are removed from the final product before reaching retail (peels, roots, and seeds), and these raw materials are rich sources of highly valuable molecules such as phytochemicals, minerals, vitamins, and other compounds with health benefits (prevention of several diseases, improvement of the immune system, regulating gastrointestinal transit, and others). Therefore, substantial efforts have been made to find technological solutions to avoid food waste, namely through its reuse in the food chain, thus promoting the circular economy and sustainability. This review focuses on the biggest wastes generated by the food industry, the most common destinations, and case studies applying these by-products or biowaste in the food industry. The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES to the CIMO (UIDB/00690/2020). M.C. Pedrosa thank FCT for her PhD grant (2021.04531.BD), S. Heleno and M. Carocho thank FCT for their individual employment program contract (CEECIND/03040/2017, CEEC-IND/00831/2018) and L. Barros also thanks FCT through the institutional scientific employment program contract for her contract. info:eu-repo/semantics/publishedVersion

Muffins are snacks made from flour and chocolate and preserved with synthetic additives. Following consumer trends, the search for natural food additives has gained traction. Plants such as rosemary, lemon balm, and oregano were analyzed following an optimization of ultrasound assisted extraction, screened for their antioxidant and antimicrobial activity and incorporated in chocolate muffins, comparing them to synthetic preservatives over the course of 8 days. The nutritional profile, organic and fatty acids, soluble sugars, texture profile, external color and digital imaging of the muffin pores were analyzed. Slight changes were sought for the muffins incorporated with the natural extracts. By means of linear discriminant analysis, rosemary extract was considered the most promising extract to preserve the muffins due to its similarity to potassium sorbate, showing no changes in the muffins it was incorporated in, although it showed a lower amount of phenolic compounds when compared to lemon balm. This research was funded by the Portuguese Foundation for Science and Technology (FCT) and the FEDER-Interreg España-Portugal programme for financial support through the project TRANSCoLAB 0612_TRANS_CO_LAB_2_. The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES to the CIMO (UIDB/00690/2020). L.B. and R.C.C. also thank the national funding by FCT—Foundation for Science and Technology, through the institutional scientific employment program-contract for their contracts and, M.C., S.H. and J.P. to the national funding by FCT—Foundation for Science and Technology, through the individual scientific employment program-contracts (CEECIND/00831/2018, CEECIND/03040/2017 and CEECIND/01011/2018). The authors are also grateful to FEDER-Interreg España-Portugal programme for financial support through the project TRANSCoLAB 0612_TRANS_CO_LAB_2_. M.C.P. and J.M.U. contributed in the same manner for this manuscript. info:eu-repo/semantics/publishedVersion

The XXI century has brought along many changes in how consumers look at food and perceive their diets. There is an increasing awareness towards what goes into manufacturing these foods, with an important concern being drawn towards food additives. While it is known that additives are needed to preserve or change attributes of food, it is also widely understood that consumers prefer natural additives to synthetic ones, and thus, the industry is looking for alternatives from plant sources. Here, the extraction of 5 different plants (oregano (Origanum vulgare L.), rosemary (Rosmarinus officinalis L.), salvia (Salvia officinalis L.), lemon balm (Melissa officinalis L.) and basil (Ocimum basilicum L.)), was optimized from three extraction types, namely decoction, infusion and cold hydroethanolic (80:20) ultrasound extraction, carried out through Response Surface Methodology (RSM) using Design Expert, pending the analysis of phenolic compounds through HPLC-DAD-ESI/MS. The variables used for RSM were temperature, time of extraction and watts (ultrasound). The extraction with the highest phenolic content for each plant was then selected and screened for its antibacterial and antifungal activity, relying on the microdilution method against foodborne pathogens, before using these extracts as natural food additives in yogurts and muffins. The bacterial species used were Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Escherichia coli, Salmonella typhimurium and Enterobacter cloacae, while the fungi species were Aspergillus fumigatus, Aspergillus niger, Aspergillus versicolor, Penicillium funiculosum, Trichoderma viride and Penicillium verrucosum var. cyclopium. Two synthetic and widely used preservatives were also screened against these contaminants, namely sodium benzoate (E211), and potassium metabisulfite (E224), while also confirming the sensitivity of the microbes with known antibiotics. Overall, the plant extracts showed a high inhibition of fungi, with all extracts showing lower minimum inhibition concentrations than both the synthetic preservatives, except for P. verrucosum, where potassium metabisulfite showed the same inhibition capacity. Regarding the antibacterial activity, the most sensitive bacteria to the extracts was S. aureus, where all showed the same activity as potassium metabisulfite. Lemon balm was the best extract of all, showing the same inhibition as sodium benzoate against B. cereus and E. cloacae. Overall, this work proves that plant extracts, obtained though “green” and cheap technologies can be alternatives to synthetic food additives, due to showing the same, or, in some cases, better antimicrobial activity. Furthermore, a mixture of these extracts can result in synergistic effects and improve the antimicrobial activities. The next step in the determination of the efficacy of these extracts is their incorporation in yogurts and muffins, which is ongoing. Acknowledgments Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020). S. Heleno and M. Carocho thank FCT for their individual research program-contract (CEECIND/00831/2018; CEECIND/03040/2017), while L. Barros thanks FCT for her institutional scientific employment program-contract.