María C. Luna

Influence of nutrient solutions in an open-field soilless system on the quality characteristics and shelf life of fresh-cut red and green lettuces (Lactuca sativa L.) in different seasons

BACKGROUND Little information is available about the impact of nutrient solution ion concentration on quality characteristics and shelf life of fresh-cut lettuce grown in soilless systems in open field. Three lettuce genotypes, lollo rosso and red oak leaf as red-leafed genotypes and butterhead as green-leafed genotype, were studied. The influence of three nutrient solutions with low, medium and high ion concentrations, which varied in the macroanion (NO₃⁻) and macrocations (K⁺, Ca²⁺ and NH₄⁺), were compared in summer and winter. RESULTS The nutrient solutions evaluated in this study for the production of lettuce in a soilless system did not strongly influence the quality characteristics of the raw material. When the ion concentration of the nutrient solution was increased, fresh weight decreased, although it depended on the genotype and season. Maturity index and dry matter content varied with the season but independently of the nutrient solution. In summer, maturity index was higher and dry matter lower than in winter. Initial texture and visual quality were not influenced by the nutrient solution. Medium ion concentration provided the highest content of vitamin C and phenolic compounds. Our observations pointed out that the genotype had a strong influence on the shelf life of the fresh-cut product with minor differences among nutrient solutions. In general, red-leafed lettuces showed the highest antioxidant content, helping the maintenance of sensory characteristics throughout storage. CONCLUSION The combination of optimal nutrient solution ion concentration and suitable cultivar is considered essential to ensure lettuce post-cutting life.

Isolation of Human Intestinal Bacteria Capable of Producing the Bioactive Metabolite Isourolithin A from Ellagic Acid

Urolithins are intestinal microbial metabolites produced from ellagitannin- and ellagic acid-containing foods such as walnuts, strawberries, and pomegranates. These metabolites, better absorbed than their precursors, can contribute significantly to the beneficial properties attributed to the polyphenols ellagitannins and ellagic acid (EA). However, both the ability of producing the final metabolites in this catabolism (urolithins A, B and isourolithin A) and the health benefits associated with ellagitannin consumption differ considerably among individuals depending on their gut microbiota composition. Three human urolithin metabotypes have been previously described, i.e., metabotype 0 (urolithin non-producers), metabotype A (production of urolithin A as unique final urolithin) and metabotype B (urolithin B and/or isourolithin A are produced besides urolithin A). Although production of some intermediary urolithins has been recently attributed to intestinal species from Eggerthellaceae family named Gordonibacter urolithinfaciens and Gordonibacter pamelaeae, the identification of the microorganisms responsible for the complete transformation of EA into the final urolithins, especially those related to metabotype B, are still unknown. In the present research we illustrate the isolation of urolithin-producing strains from human feces of a healthy adult and their ability to transform EA into different urolithin metabolites, including isourolithin A. The isolates belong to a new genus from Eggerthellaceae family. EA transformation and urolithin production arisen during the stationary phase of the growth of the bacteria under anaerobic conditions. The HPLC-DAD-MS analyses demonstrated the sequential appearance of 3,8,9,10-tetrahydroxy-urolithin (urolithin M6), 3,8,9-trihydroxy-urolithin (urolithin C) and 3,9-dihydroxy-urolithin (isourolithin A) while 3,8-dihydroxy-urolithin (urolithin A) and 3-hydroxy-urolithin (urolithin B) were not detected. For the first time isourolithin A production capacity of pure strains has been described. The biological activity attributed to urolithins A and B and isourolithin A (anti-inflammatory, anti-carcinogenic, cardioprotective, and neuroprotective properties) explains the relevance of identifying these urolithin-producing bacteria as potential novel probiotics with applications in the development of functional foods and nutraceuticals. Their human administration could improve the health benefits upon ellagitannin consumption, especially in metabotype 0 individuals. However, further research is necessary to probe well-established beneficial effects on the host and safety requirements before being considered among the next-generation probiotics.

Effects of salt stress on physiological and postharvest quality characteristics of different Iranian genotypes of basil

This study examined the effects of salt stress on the physiological responses and postharvest quality characteristics of fresh sweet basil (Ocimum basilicum L.). Plants were treated with 40 and 80 mM NaCl for 25 days during cultivation in 2014. Two green genotypes, Green Iranian and Genovese basil, were studied after harvest, and while two Iranian genotypes, Green and Purple Iranian basil, were compared during storage. Yield and the stem length were significantly reduced under salt stress only in the two Iranian cultivars. Salinity significantly reduced leaf thickness and the area of parenchyma cells in both Green Iranian and Genovese basil. As salt concentration increased, transpiration and the content of chlorophylls decreased significantly while the lipid peroxidation increased in the Genovese genotype. During storage at 12°C, the respiration rate of salt-stressed leaves was similar to that of control leaves. The visual quality of Purple Iranian basil was better preserved during storage than the Green Iranian basil. However, salt stress positively affected the visual quality of Green Iranian basil, decreasing darkening and maintaining the quality above the limit of marketability after 7 days of storage. The total content of phenolic acids and anthocyanins did not show significant differences between growth conditions. However, during storage of Green Iranian basil, salt stress increased the content of individual and total phenolic acids compared to the control. To summarize, the positive or negative effects of salt stress on basil depend on the degree of tolerance of the different genotypes.

Ultrasound treatments improve the microbiological quality of water reservoirs used for the irrigation of fresh produce

Irrigation water has been highlighted as a source of microbial contamination in produce. Water treatment has been recommended as an intervention strategy to reduce microbial risks associated to irrigation water. Commercial water treatments mostly depend on chemical agents; although growers search for greener alternatives to chemical biocides. Ultrasounds (US) have been proposed as an environmentally friendly technology for irrigation water. In the present study, the suitability of two US treatments (20kHz: US20 and 40kHz: US40 at a specific energy (Es) of 745J/L) and one chlorine treatment (1-2ppm free chlorine) was evaluated and compared to the untreated control. Five water reservoirs belonging to five commercial intensive farms were selected as representative of irrigation practices generally used in south of Europe. All tested water treatments were able to reduce microbial loads, including Escherichia coli (0.5-0.6 log units), to values that were accepted in most of the recommended guidelines of good agricultural practices (≤2logunits). The obtained reductions were lower than those previously reported for these water treatment technologies in lab-scale tests. High microbial reductions are commonly obtained in laboratory studies, yielding impressive results. However, when the same treatments are applied under real commercial conditions, microbial reductions are usually less impressive. All water treatments were able to reduce COD of irrigation water when compared to the untreated control. COD reductions obtained using chlorine (≥430mg/L) and US 20 (~100mg/L) were higher than those observed using US 40 (<50mg/L). The impact of the water quality on the efficacy of US treatments was evaluated in two types of water including surface water and treated wastewater. It was found that the quality of the irrigation water significantly influences the efficacy of the ultrasound treatment. Correlations between indicator parameters have been also evaluated. Obtained results showed that high algae counts were well correlated with high levels of coliforms and E. coli. It could be concluded that US can be proposed as an alternative water treatment to chemical treatments to preserve microbial quality of irrigation water stored in water reservoirs reducing the environmental impact.

Influence of water stress and storage time on preservation of the fresh volatile profile of three basil genotypes

The main goal of the present study was to describe the volatile profile of three different basil genotypes (Genovese and Green and Purple Iranian), and the impact that water stress (75% and 50% field capacity) and storage time (up to 7days) have under mild refrigerated conditions. The chromatographic profile pointed to three different chemotypes: linalool/eugenol, neral/geranial, and estragol, for Genovese, Green, and Purple genotypes, respectively. Water stress depleted the volatile profile of these three landraces, due to a reduction in the absolute concentrations of some of the components related to fresh aroma (linalool, nerol, geraniol and eugenol). The stability of the basil volatile profile during storage varied depending on the water stress that had been applied. Concentration reductions of close to 50% were quantified for most of the components identified in the Purple genotype.

Effect of Water Stress and Storage Time on Anthocyanins and Other Phenolics of Different Genotypes of Fresh Sweet Basil

This study describes the effect of water stress and storage time on the content of anthocyanins and other phenolics in different genotypes of fresh sweet basil (Ocimum basilicum L.). Purple and green Iranian cultivars and a Genovese variety were exposed to a control (100% of the field capacity, FC) and to water stress of mild and severe deficit irrigation treatments (25 and 50 DI corresponding to 75 and 50% FC, respectively). The individual characterization by HPLC-DAD-ESI/MS(n) and the MS fragmentation pathway of anthocyanins are described. A 50% increase in the anthocyanin content was observed in 50 DI after storage. Water stress markedly enhanced the content of phenolic acids after storage in the three genotypes. Water stress can be an efficient way to help the sustainability of water resources, enriching the content of phenolic compounds that may be beneficial to human health.