Variations of peel essential oils during fruit ripening in four lemon (Citrus limon (L.) Burm. F.) cultivars

Lemon processing procedures yield a significant amount of waste as peels, which are 57% of processed lemons and represent a possible source of bioactive compounds (essential oils, EOs). EOs were extracted from lemon fruits belonging to four cultivars harvested at four different sampling times (25 October, 23 November, 20 December, 1 February), characterized, and quantified through gas chromatography-mass spectrometry

Morphological characteristics, ascorbic acid and antioxidant activity during fruit ripening of four lemon (Citrus limon (L.) Burm. F.) cultivars

Citrus limon (L.) Burm contains many important natural bioactive compounds, such as ascorbic acid, essential oils, and antioxidant substances. An experiment was carried out on four lemon cultivars (Ovale di Sorrento, Sfusato Amalfitano, Femminello Cerza and Femminello Adamo) from Southern Italy to study the changes in physico-chemical properties of juice during fruit ripening. Morphological characteristics of fruits, total soluble solids, pH and titratable acidity, ascorbic acid (AsA), and antioxidant activity (TEAC) of juice were tested. The concentrations of AsA in lemon juice showed significant differences among cultivars and ripening stages, with a steadily decrease along ripening stages: from 31.38 of stage I to 23.71 mg 100 g−1 of stage IV. The juice AsA concentration correlated with the colorimetric parameters of peel: L (r = −0.643), a (r = −0.719) and b (r = −0.654). The cv Ovale di Sorrento showed the highest average AsA concentration (29.91 mg 100 g-1). The level of the total TEAC showed a significant steadily decrease from the first to the fourth ripening stage that on average approached 38 %. Principal component analysis showed that lemon fruits at the ripening stages II and III were highly similar each other and well discriminated from the first and last ripening stages that also performed more distantly each other. The paper provides in-depth knowledge about the trend in AsA content and antioxidant activity of lemon juice across ripening

Can Lunar and Martian Soils Support Food Plant Production? Effects of Horse/Swine Monogastric Manure Fertilisation on Regolith Simulants Enzymatic Activity, Nutrient Bioavailability, and Lettuce Growth

To make feasible the crewed missions to the Moon or Mars, space research is focusing on the development of bioregenerative life support systems (BLSS) designed to produce food crops based on in situ resource utilisation (ISRU), allowing to reduce terrestrial input and to recycle organic wastes. In this regard, a major question concerns the suitability of native regoliths for plant growth and how their agronomic performance is affected by additions of organic matter from crew waste. We tested plant growth substrates consisting of MMS-1 (Mars) or LHS-1 (Lunar) simulants mixed with a commercial horse/swine monogastric manure (i.e., an analogue of crew excreta and crop residues) at varying rates (100:0, 90:10, 70:30, 50:50, w/w). Specifically, we measured: (i) lettuce (Lactuca sativa L. cultivar ‘Grand Rapids’) growth (at 30 days in open gas exchange climate chamber with no fertilisation), plant physiology, and nutrient uptake; as well as (ii) microbial biomass C and N, enzymatic activity, and nutrient bioavailability in the simulant/manure mixtures after plant growth. We discussed mechanisms of different plant yield, architecture, and physiology as a function of chemical, physicohydraulic, and biological properties of different substrates. A better agronomic performance, in terms of plant growth and optically measured chlorophyll content, nutrient availability, and enzymatic activity, was provided by substrates containing MMS-1, in comparison to LHS-1-based ones, despite a lower volume of readily available water (likely due to the high-frequency low-volume irrigation strategy applied in our experiment and foreseen in space settings). Other physical and chemical properties, along with a different bioavailability of essential nutrients for plants and rhizosphere biota, alkalinity, and release of promptly bioavailable Na from substrates, were identified as the factors leading to the better ranking of MMS-1 in plant above and below-ground mass and physiology. Pure Mars (MMS-1) and Lunar (LHS-1) simulants were able to sustain plant growth even in absence of fertilisation, but the amendment with the monogastric manure significantly improved above- and below-ground plant biomass; moreover, the maximum lettuce leaf production, across combinations of simulants and amendment rates, was obtained in treatments resulting in a finer root system. Increasing rates of monogastric manure stimulated the growth of microbial biomass and enzymatic activities, such as dehydrogenase and alkaline phosphomonoesterase, which, in turn, fostered nutrient bioavailability. Consequently, nutrient uptake and translocation into lettuce leaves were enhanced with manure supply, with positive outcomes in the nutritional value of edible biomass for space crews. The best crop growth response was achieved with the 70:30 simulant/manure mixture due to good availability of nutrients and water compared to low amendment rates, and better-saturated hydraulic conductivity compared to high organic matter application. A 70:30 simulant/manure mixture is also a more sustainable option than a 50:50 mixture for a BLSS developed on ISRU strategy. Matching crop growth performance and (bio)chemical, mineralogical, and physico-hydraulic characteristics of possible plant growth media for space farming allows a better understanding of the processes and dynamics occurring in the experimental substrate/plant system, potentially suitable for an extra-terrestrial BLSS