Postharvest yellow LED lighting affects phenolics and glucosinolates biosynthesis in broccoli sprouts

Combined effect of an agro-industrial compost and light spectra composition on yield and phytochemical profile in mizuna and pak choi microgreens

This work aimed to evaluate the growth of two species of microgreens (mizuna and pak choi), using agro-industrial compost as growing media in two different mixes versus one hundred percent peat, under two different LED illumination spectra (LED 1 and LED 2) in a 14 h photoperiod. The experiment was carried-out for two times. Biomass yield, glucosinolates, and phenolic compounds, and nitrate (NO3-) content were analysed in leaf tissues. In both species, the highest fresh and dry biomass production was in compost:peat (50:50%) and LED 2 (Blue/Red/Far Red). In general, compost had a greater influence on nitrate content than light, but in the microgreen pak choi, the anthocyanin content was inhibited by the compost treatment. In the other hand both LED illumination had a positive effect on mizuna for glucosinolates and anthocyanins, and LED 2 also showed a positive effect on pak choi for anthocyanin. Therefore, the use of agri-food compost: peat (50:50%) with LED 2 (blue/red) lighting treatment to obtain microgreens in indoor crops is a plausible technology that provides nutritionally and phytochemically rich crops.

Ultrasounds and a Postharvest Photoperiod to Enhance the Synthesis of Sulforaphane and Antioxidants in Rocket Sprouts

Ultrasounds (US) and LED illumination are being studied to optimize yield and quality. The objective was to evaluate the effect of a pre-sowing US treatment combined with a postharvest photoperiod including LEDs on rocket sprouts’ quality and phytochemicals during shelf life. A US treatment (35 kHz; 30 min) applied to seeds and a postharvest photoperiod of 14 h fluorescent light (FL) + 10 h White (W), Blue (B), Red (R) LEDs or Darkness (D) were assayed. Antioxidants as phenolics and sulfur compounds (glucosinolates and isothiocyanates) were periodically monitored over 14 days at 5 °C. The US treatment increased the sulforaphane content by ~4-fold compared to CTRL seeds and sprouts. The phenolic acids and the flavonoid biosynthesis were enhanced by ~25%, ~30%, and ~55% under photoperiods with W, B, and R, respectively, compared to darkness. The total glucosinolate content was increased by >25% (W) and >45% (B and R) compared to darkness, which also reported increases of ~2.7-fold (W), ~3.6-fold (B), and ~8-fold (R) of the sulforaphane content as a main isothiocyanate. Postharvest lighting is an interesting tool to stimulate the secondary metabolism, while a US treatment was able to increase the sulforaphane content in seeds and sprouts, although no synergistic effect was reported.

Influence of sequential exogenous pretreatment and contact ultrasound-assisted air drying on the metabolic pathway of glucoraphanin in broccoli florets

In this investigation, the combinations of exogenous pretreatment (melatonin or vitamin C) and contact ultrasound-assisted air drying were utilized to dry broccoli florets. To understand the influences of the studied dehydration methods on the conversion of glucoraphanin to bioactive sulforaphane in broccoli, various components (like glucoraphanin, sulforaphane, myrosinase, etc.) and factors (temperature and moisture) involved in the metabolism pathway were analyzed. The results showed that compared with direct air drying, the sequential exogenous pretreatment and contact ultrasound drying shortened the drying time by 19.0-22.7%. Meanwhile, contact sonication could promote the degradation of glucoraphanin. Both melatonin pretreatment and vitamin C pretreatment showed protective effects on the sulforaphane content and myrosinase activity during the subsequent drying process. At the end of drying, the sulforaphane content in samples dehydrated by the sequential melatonin (or vitamin C) pretreatment and ultrasound-intensified drying was 14.4% (or 26.5%) higher than only air-dried samples. The correlation analysis revealed that the exogenous pretreatment or ultrasound could affect the enzymatic degradation of glucoraphanin and the generation of sulforaphane through weakening the connections of sulforaphane-myrosinase, sulforaphane-VC, and VC-myrosinase. Overall, the reported results can enrich the biochemistry knowledge about the transformation of glucoraphanin to sulforaphane in cruciferous vegetables during drying, and the combined VC/melatonin pretreatment and ultrasound drying is conducive to protect bioactive sulforaphane in dehydrated broccoli.

Enhancement of Glucosinolate Formation in Broccoli Sprouts by Hydrogen Peroxide Treatment

Broccoli sprouts are known as a rich source of health-beneficial phytonutrients: glucosinolates and phenolic compounds. The production of phytonutrients can be stimulated by elicitors that activate the plant stress response. The aim of this study was enhancing the nutritional value of broccoli sprouts using hydrogen peroxide (H₂O₂) as an elicitor. Daily spraying with H₂O₂ (500-1000 mM) enhanced the accumulation of glucosinolates, doubling their content in the cotyledons of 16/8 h photoperiod-grown 7-day sprouts compared to the water-treated controls. The application of H₂O₂ on dark-grown sprouts showed a smaller extent of glucosinolate stimulation than with light exposure. The treatment affected sprout morphology without reducing their yield. The H₂O₂-treated sprouts had shorter hypocotyls and roots, negative root tropism and enhanced root branching. The activated glucosinolate production became evident 24 h after the first H₂O₂ application and continued steadily until harvest. Applying the same treatment to greenhouse-grown wild rocket plants caused scattered leaf bleaching, a certain increase in glucosinolates but decline in phenolics content. The H₂O₂ treatment of broccoli sprouts caused a 3.5-fold upregulation of APK1, a gene related to sulfur mobilization for glucosinolate synthesis. Comparing the APK1 expression with the competing gene GSH1 using sulfur for antioxidant glutathione production indicated that glutathione synthesis prevailed in the sprouts over the formation of glucosinolates.

UV and Visible Spectrum LED Lighting as Abiotic Elicitors of Bioactive Compounds in Sprouts, Microgreens and Baby Leaves. A Comprehensive Review Including Their Mode of Action

According to social demands, the agri-food industry must elaborate convenient safe and healthy foods rich in phytochemicals while minimising processing inputs like energy consumption. Young plants in their first stages of development represent great potential. Objective: This review summarises the latest scientific findings concerning the use of UV and visible spectrum LED lighting as green, sustainable, and low-cost technologies to improve the quality of sprouts, microgreens, and baby leaves to enhance their health-promoting compounds, focusing on their mode of action while reducing costs and energy. Results: These technologies applied during growing and/or after harvesting were able to improve physiological and morphological development of sprouted seeds while increasing their bioactive compound content without compromising safety and other quality attributes. The novelty is to summarise the main findings published in a comprehensive review, including the mode of action, and remarking on the possibility of its postharvest application where the literature is still scarce. Conclusions: Illumination with UV and/or different regions of the visible spectrum during growing and shelf life are good abiotic elicitors of the production of phytochemicals in young plants, mainly through the activation of specific photoreceptors and ROS production. However, we still need to understand the mechanistic responses and their dependence on the illumination conditions.

By-Products Revalorization with Non-Thermal Treatments to Enhance Phytochemical Compounds of Fruit and Vegetables Derived Products: A Review

The aim of this review is to provide comprehensive information about non-thermal technologies applied in fruit and vegetables (F&V) by-products to enhance their phytochemicals and to obtain pectin. Moreover, the potential use of such compounds for food supplementation will also be of particular interest as a relevant and sustainable strategy to increase functional properties. The thermal instability of bioactive compounds, which induces a reduction of the content, has led to research and development during recent decades of non-thermal innovative technologies to preserve such nutraceuticals. Therefore, ultrasounds, light stresses, enzyme assisted treatment, fermentation, electro-technologies and high pressure, among others, have been developed and improved. Scientific evidence of F&V by-products application in food, pharmacologic and cosmetic products, and packaging materials were also found. Among food applications, it could be mentioned as enriched minimally processed fruits, beverages and purees fortification, healthier and "clean label" bakery and confectionary products, intelligent food packaging, and edible coatings. Future investigations should be focused on the optimization of 'green' non-thermal and sustainable-technologies on the F&V by-products' key compounds for the full-utilization of raw material in the food industry.