Innovative Olive Tree Leaves Shredder Prototype for the Valorization of Wasted Leaves: An Application to High-Quality Compost Production

Extra virgin olive oil is considered worldwide as one of the most important products, a standard bearer of the Mediterranean diet. Despite this, the production chain of extra virgin olive oil generates four times more waste than quantity of oil. For this reason, the disposal of olive mill wastes represents a significant environmental problem in all the Mediterranean countries. In this direction, several innovations and improvement strategies were proposed in the literature to correctly manage these by-products and, in some cases, to valorize them by the recovery of polyphenols and other interesting substances. However, innovations and improvement strategies for the valorization of olive tree leaves are definitely neglected in the literature, thus motivating this work. The aims of this work are as follow: firstly, to develop and test an innovative olive tree leaves shredder prototype to help olive oil millers in the management of waste leaves deriving from pruning and olive oil production; secondly, to test the combination of the minced olive tree leaves with other by-products in the production of high-quality compost. The results showed the effectiveness of the tested olive tree leaves shredder in significantly reducing the volume occupied by the leaves by 40%. Moreover, the mixing of the minced olive tree leaves with other by-products lead to a high-quality compost which, in accordance with Italian legislation, could even be certified and labeled with this denomination. Future research will investigate the quantification of the benefits in terms of environmental impacts using life cycle assessment.

HPLC-HRMS Global Metabolomics Approach for the Diagnosis of “Olive Quick Decline Syndrome” Markers in Olive Trees Leaves

Olive quick decline syndrome (OQDS) is a multifactorial disease affecting olive plants. The onset of this economically devastating disease has been associated with a Gram-negative plant pathogen called Xylella fastidiosa (Xf). Liquid chromatography separation coupled to high-resolution mass spectrometry detection is one the most widely applied technologies in metabolomics, as it provides a blend of rapid, sensitive, and selective qualitative and quantitative analyses with the ability to identify metabolites. The purpose of this work is the development of a global metabolomics mass spectrometry assay able to identify OQDS molecular markers that could discriminate between healthy (HP) and infected (OP) olive tree leaves. Results obtained via multivariate analysis through an HPLC-ESI HRMS platform (LTQ-Orbitrap from Thermo Scientific) show a clear separation between HP and OP samples. Among the differentially expressed metabolites, 18 different organic compounds highly expressed in the OP group were annotated; results obtained by this metabolomic approach could be used as a fast and reliable method for the biochemical characterization of OQDS and to develop targeted MS approaches for OQDS detection by foliage analysis.

Olive Tree Leaves—A Source of Valuable Active Compounds

The agricultural and processing activities of olive crops generate a substantial amount of food by-products, particularly olive leaves, which are mostly underexploited, representing a significant threat to the environment. Olive leaves are endowed with endogenous bioactive compounds. Their beneficial/health-promoting potential, together with environmental protection and circular economy, merit their exploitation to recover and reuse natural components that are potentially safer alternatives to synthetic counterparts. These biomass residues have great potential for extended industrial applications in food/dietary systems but have had limited commercial uses so far. In this regard, many researchers have endeavoured to determine a green/sustainable means to replace the conventional/inefficient methods currently used. This is not an easy task as a sustainable bio-processing approach entails careful designing to maximise the liberation of compounds with minimum use of (i) processing time, (ii) toxic solvent (iii) fossil fuel energy, and (iv) overall cost. Thus, it is necessary to device viable strategies to (i) optimise the extraction of valuable biomolecules from olive leaves and enable their conversion into high added-value products, and (ii) minimise generation of agro-industrial waste streams. This review provides an insight to the principal bioactive components naturally present in olive leaves, and an overview of the existing/proposed methods associated with their analysis, extraction, applications, and stability.

Synthetic vs. Natural Hydroxytyrosol for Clean Label Lamb Burgers

Clean labelling refers to consumers’ desire for manufacturers to be more transparent in the way their products are made and sourced. Natural antioxidants (spices, herbs, fruits, or vegetables) have been proven to offer the same functionality as their synthetic counterparts, with the advantage of being label friendly and process compatible, maintaining meat quality and reducing food waste. Lamb meat has the challenges to have an intense flavour and fat composition to test the effectiveness of some of these natural antioxidants like hydroxytyrosol (HXT). The current paper was designed to test both natural (HXTo) and synthetic (HXTs) antioxidants using four lamb patty batches: one Control (C) (which included sulphites); a reference (R) sample (14.6% carnosic acid and 6% carnosol from natural rosemary extracts, 200 ppm); a sample containing synthetic hydroxytyrosol (HXTs, 99% purity, 200 ppm); and a sample with added organic hydroxytyrosol (HXTo, sample 7% purity from olive tree leaves, 200 ppm). A shelf-life study was carried out for 6 days at 4 °C, testing proximal composition and mineral bioavailability, pH changes, colour (by CIELab), total antioxidant capacity (TAC by oxygen radical absorbance capacity (ORAC)), lipid and protein oxidation (thiobarbituric acid reactive substances (TBARs) and thiol loss, respectively), volatile compound profiles (by HPC-MS), sensory evaluation, and microbiological growth (as total vial count (TVC) and total coliform count (TCC)). Results revealed that lamb burgers with added HXTs had better-preserved raw lamb meat in the test conditions, with reduced colour losses, lipid oxidation, and release of volatile compounds, the half the microbiological growth (TVC) of the Control, the best TAC, and significantly increased (p < 0.05) minerals bioavailability, while maintaining sensory acceptability. In summary, natural antioxidants are an adequate strategy for lamb meat burgers. Regarding HXTo, obtained from olives, the synthetic analogue is even more effective in terms of preservative and antioxidant activity, and in maintaining the nutritional value, sensory characteristics, and safety of food products.

Acid Hydrolysis of Olive Tree Leaves: Preliminary Study towards Biochemical Conversion

Olive tree leaves, an abundant agricultural by-product without enough industrial market outlets, are presented in this study as a relevant resource of available carbohydrates to be chemically treated for monomeric sugar production. Characterization of two main granulometric fractions is the starting point for testing the specific effect and the relevance of three main factors (time, temperature, and sulfuric acid concentration) on diluted acid hydrolysis with respect to oligosaccharides, simple sugars, and fermentation inhibitory compounds production. The selected conditions (100 ∘ C, 90 min, and 6% w/w H 2 SO 4 ) to perform the small scale hydrolytic process, considering response surface methodology (2 3 factorial design with center points), implied production of acetic acid and hydroxymethylfurfural in concentrations not exceeding 1.10 kg m − 3 and 0.25 kg m − 3 , respectively. Thus, these experimental conditions were the reference framework to evaluate the effect of a meaningful scaling stage in a hydrolysis reactor, considering kinetic parameters based on hydrolysis rates and d-glucose and d-xylose generation.