The value of the concept of retention indices (RI) to the practice of gas chromatography (GC) is highlighted, where the RI of a compound is one component of the strategy to identify the compound. The widespread reliance on GC and then on mass spectrometry for 'identification', may result in inadequate confirmation of molecular identity. However, RI do provide a useful tentative indication of the possible molecule(s). Thus, the RI value is a useful first measure of the molecule identity, and shown here to be valuable provided limitations are recognised. An author has a responsibility to correctly calculate the index and then use the values for (tentative) identification. Tables of reference RI values are useful in this respect, but finding an 'exact match' RI value does not confirm the identity. Hence, it is necessary to understand how the RI value may be incorrectly used in this respect. The reviewer of written research is charged with ensuring the index values are applied in a rigorous manner. Selected case studies from our own work, support the care that must be exercised when reporting RI values. In terms of advanced GC operations, mention is made of multidimensional gas chromatography and comprehensive two-dimensional gas chromatography to acquire RI values on both the first and second columns in the two-column separation experiment.

Open access peer-reviewed chapter

The chemical composition of the essential oils of Mentha arvensis and Mentha piperita and their antimicrobial activity against twelve Aeromonas spp. isolates from tambaquis (Colossoma macropomum), an important native farmed fish species in Brazil, were evaluated. The oils were characterized using gas chromatography and mass spectrometry (GC/MS) and their antimicrobial activity was evaluated through the microdilution method. The essential oils of these Mentha species mainly comprised oxygenated monoterpenes (97.1% for M. arvensis and 86.2% for M. piperita) and menthol was the major compound of these oils (86.1% for M. arvensis and 33.8% for M. piperita). It was confirmed that these oils had antimicrobial activity against 12 isolates of Aeromonas spp., with minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) ranging from 1,250 to 16,666.7 μg mL⁻¹. Better antimicrobial activity was achieved by the M. arvensis essential oil.

Agriculture and food science literature on waste-to-value applications that allow upcycling of by-product ingredients is increasing. However, this stream of research rarely takes an international trade and sustainability systems perspective. This focused review defines the term of waste-to-value and the sustainable development goals connected to it, and points to the tensions and questions arising when international trade is involved. Further, it exemplifies the challenges and opportunities of waste-to-value in tropical fruit trade through five cases of tropical fruit from South America: Green coconut, açaí, maracujá, cambuci, and jabuticaba. We present a model of the international supply chain that indicates where the opportunities of waste-to-value applications in international tropical fruit trade are situated, and discuss which future research questions need to be addressed to tackle the challenges of waste-to-value in global tropical fruit chains. Establishing the waste-to-value approach in the export of yet-underused tropical fruits can amongst others improve local employment, preserve natural resources, allow favorable use of side-streams in local energy production, environmentally friendly packaging material for transport, and add health functionalities to the end-consumer products, but challenges have to be solved in order to ensure these environmental and social benefits materialize.