Agro-food Residues Research Articles

Suitability of different organic amendments from agro-industrial wastes in organic lettuce crops

An inadequate replacement of organic matter in agricultural lands progressively leads to soil fertility reduction and therefore, soil application of organic fertilizers and amendments should be promoted. The objectives of this 3-year research project on organic lettuce were to investigate the agronomic performance of experimental organic amendments obtained by using agro-industrial wastes in comparison with a commercial organic fertilizer, and to evaluate their short-term effects on soil mineral-N and soil organic carbon changes. Two types of olive pomace mixtures, with different initial C/N ratios, were composted and either stopped at the active phase (A1 and B1) or processed until maturation (A2 and B2). Also an anaerobic digestate (DA) and the B2 in combination with mineral fertilizer (B2-MIN) were studied. The four composts, DA and B2-MIN were compared with a commercial organic fertilizer (Org), and an unfertilized control (N0). Results suggested that the best compromise for organic lettuce yield and soil fertility could be obtained with the B2 compost, thus highlighting the need for choosing a good stage of maturity of the compost, along with an appropriate C/N ratio of composting mixture, to improve the fertilizing efficiency of agro-food residues in organic farming. Furthermore, the application of immature amendments did not increase (B1) or significantly reduce (A1) marketable lettuce yield, indicating that the choice of organic fertilizer is an important concern in sustainable agriculture, especially in organic vegetable production.

LIMITED ACCESS TO RESOURCES: CHALLENGES OR OPPORTUNITIES?

In many countries sustainability is an important driver for many of policies: nearly all the already enforced or forthcoming regulations include sustainability aspects. But sustainability is not solely about wise and equitable use of resources or climate change adaptive actions, it also concerns waste reduction, minimizing energy, water and land consumption making efficient use of any kind of external inputs, in the frame of a broader bio economy concept. Coupling Bio and Circular economy concepts is deemed our best option to finally achieve a sustainable production of food, functional and nutraceutic compounds, industrial products and energy. In this new economy, the definition of biomass incompasses any biological material to be used, or reused, as raw material in the same or in interconnected productive processes. The focus on total harvested biomasses, instead on the primary product it is probably one of the most innovative concepts backing future economic growth. As a matter of fact, it can play an important role in both creating economic growth, in stimulating technological development and in formulating effective adaptation to global challenges. Nevertheless, the first impact of sustainability criteria applied to the current economic model has been an increased competition on the main resources, namely: i) water; ii) land; iii) external inputs –i.e., energy, nutrients, chemicals; iv) capital, both financial and human. Farmers, academy and industry will have to adjust and re-orient their programmes in order to develop new farm and food production systems, in line with new policies and external drivers. The new agro-food production systems must be designed in order to match the following constraints/criteria: i) ensure profitability at farm level; ii) production of the consistent quality raw materials required by food processing and by bio refineries; iii) produce internationally tradable food products and related know-how and technologies; iv) improved energy efficiency at each step of the production chain; v) increasing resilience and self-sustainability, coping with the progressive onset of climate change; vi) secure environmental and social sustainability. Hence, significant outcomes from genomics, agronomy, food science and technology are necessary. Among the most significant and promising innovation there are: i) precision farming and irrigation; ii) nanotechnology and bio-nanotech; iii) robotics and mechatronics applications; iv) genomic and plant molecular physiology studies; v) increased use of second generation biomass, like agro-food residues and non-edible or non-commercial oils. Current limitation of resources availability is giving stimulus to innovation in the whole agro-food sector, challenging farmers and industries.

Extraction and characterization of bio-effectors from agro-food processing by-products as plant growth promoters

Recently, a novel concept ‘bio-effectors’ rose on to describe a group of products that are able to improve plant performance rather than fertilizers. Agro-food processing residues and by-products potentially represent important sources of bio-effectors but they are currently not properly taken in consideration. To fulfill this gap, in these study, three food processing by-products: (i) brewers' spent grain, (ii) fennel processing residues, and (iii) lemon processing residues were chosen as bio-effector candidates. Raw materials were chemically characterized, and green extraction methodology was optimized by using water, ethanol, and their mixture based on the extraction yields. Aqueous extracts were used for seed germination bioassays on Lepidium sativum seeds to evaluate their potential bioactivities. Thereafter, the extracts were chemically characterized and metabolites were detected by 1D and 2D NMR spectroscopy. Results are summarized as follows: (i) raw materials showed an interesting nutritional content; (ii) aqueous extraction resulted higher yield more than other used solvent; (iii) at high solvent extraction ratio, aqueous extracts were not phytotoxic but enhanced seed germination and root elongation; (iv) all aqueous extracts are differently rich in nutrients, amino-acids, sugars, and other low molecular weight molecule compounds. This study confirmed that efficient and simple recovery of bioactive compounds other than nutrients from agro-food processing by-products appear to be the new frontier in their valorization.

Evaluation of the potential of squash pumpkin by-products (seeds and shell) as sources of antioxidant and bioactive compounds

The transformation of byproducts and wastes generated by agro-food companies is of high importance since only a small portion of plant material is utilized directly for human consumption. Squash pumpkin is greatly used in Portugal and as by-products of its processing are generated tons of shell and seeds. In this study we aim to evaluate the potential of these wastes as sources of beneficial and bioactive compounds (antioxidants and antimicrobials), studying the effect of different extraction solvents and drying methods. The samples (fresh and cooked) were freeze-dried and oven-dried followed by extraction with different solvents that revealed the following decreasing order of efficiency: 70% ethanol, 70% methanol, 70% acetone, ultra-pure water and 100% dichloromethane. The oven-dried samples showed higher values of antioxidant activity and phenolic content, with exception of the values of phenolics for the seeds material. The shell samples presented higher values (1.47 - 70.96% inhibition) of antioxidant activity and total phenolic content (2.00 - 10.69mg GAE/g DW). A positive correlation was found between these two parameters on the shell samples, however the squash seeds revealed a negative correlation between the phenolic content and the antioxidant activity. The results show that these industrial agro-food residues are potentially good sources of bioactive compounds with health benefits.

Pentoses and Hydroxycinnamic Acids in Brewer's Spent Grain

In this work, the total pentose (xylose and arabinose) and hydroxycinnamic acid (ferulic and p -coumaric acids) in eight lots of brewer's spent grain preserved by different methods (freeze-drying, oven drying and freezing) has been determined. The total acid-extractable pentose content of the samples varied between 13·0 and 19·5% dry weight for xylose, and 7·2 and 9·6% dry weight for arabinose, whereas the total alkali-extractable hydroxycinnamic acid content varied between 0·17 and 0·24% dry weight for ferulic acid, and between 0·068 and 0·121% dry weight for p -coumaric acid. Significant differences (p<0·05) between lots were found for ferulic and p -coumaric acids. With respect to the different preservation methods, significant differences (P<0·05) were only seen in arabinose content. The content of pentoses and hydroxycinnamic acids in brewer's spent grain has been compared with those from other agro-food residues whose use is also proposed for the enzymatic release of these compounds.