The Impact of Domestic Cooking Methods on Myrosinase Stability, Glucosinolates and Their Hydrolysis Products in Different Cabbage (Brassica oleracea) Accessions

Glucosinolate hydrolysis products are responsible for the health-promoting properties of Brassica vegetables. The impact of domestic cooking on the myrosinase stability, glucosinolates and hydrolysis products in 18 cabbage accession was investigated. Cabbages were steamed, microwaved, and stir-fried before analysis. Cooking significantly affected myrosinase stability and glucosinolate concentrations within and between cabbage morphotypes. Myrosinase was most stable after stir-frying, with up to 65% residual activity. Steaming and microwaving resulted in over 90% loss of myrosinase activity in some accessions. Stir-frying resulted in the greatest decrease in glucosinolate concentration, resulting in up to 70% loss. Steamed cabbages retained the highest glucosinolates after cooking (up to 97%). The profile and abundance of glucosinolate hydrolysis products detected varied across all cooking methods studied. Cooking reduced the amounts of nitriles and epithionitriles formed compared to raw samples. Steaming led to a significant increase in the concentration of beneficial isothiocyanates present in the cabbage and a significantly lower level of nitriles compared to other samples. Microwaving led to a reduction in the concentrations of both nitriles and isothiocyanates when compared to other cooking methods and raw cabbage. The results obtained help provide information on the optimal cooking methods for cabbage, suggesting that steaming may be the best approach to maximising beneficial isothiocyanate production.

Methyl Jasmonate Treatment of Broccoli Enhanced Glucosinolate Concentration, Which Was Retained after Boiling, Steaming, or Microwaving

Exogenous methyl jasmonate (MeJA) treatment was known to increase the levels of neoglucobrassicin and their bioactive hydrolysis products in broccoli (Brassica oleracea var. italica), but the fate of MeJA-induced glucosinolates (GSLs) after various cooking methods was unknown. This study measured the changes in GSLs and their hydrolysis compounds in broccoli treated with MeJA and the interaction between MeJA and cooking treatments. All cooked MeJA-treated broccoli contained significantly more GSLs than untreated broccoli (p < 0.05). After 5 min of cooking (boil, steam, microwave), MeJA-treated broccoli still contained 1.6- to 2.3-fold higher GSL content than untreated broccoli. Neoglucobrassicin hydrolysis products were also significantly greater in steamed and microwaved MeJA-treated broccoli. The results show that exogenous MeJA treatment increases neoglucobrassicin and its hydrolysis compounds in broccoli even after cooking. Once the positive and negative effects of these compounds are better understood, the results of this experiment can be a valuable tool to help food scientists, nutrition scientists, and dieticians determine how to incorporate raw or cooked broccoli and Brassica vegetables in the diet.

The Effect of Fertilization with Sulphur, Boron, and Amino Acids on the Content of Glucosinolate in Winter Rape Seeds

The study was carried out in 2016–2019 at the Zawady Agricultural Experimental Station (52°03’ N and 22°33’ E) belonging to the University of Natural Sciences and Humanities in Siedlce, in Poland. The field experiment was established in a split-plot design with three replicates. The studied factors were: I. Three winter rape morphotypes: population morphotype (Monolit variety); restored morphotype with traditional growth type (PT248 variety); restored morphotype with a semi-dwarf growth type (PX115 variety); II. Types of foliar nutrition: (1) control variant—sprayed with water, without foliar nutrition and amino acids; (2) biostimulant Aminoplant; (3) foliar fertilizer Siarkomag + foliar fertilizer Bormax; (4) foliar fertilizer Siarkomag + foliar fertilizer Bormax + biostimulant Aminoplant. The aim of the study was to determine the effect of foliar application of sulphur, boron, and amino acids on the content of glucosinolates in seeds of three winter rape morphotypes (Monolit, PX115, and PT248). The foliar feeding applied reduced the feed value of winter rape seeds. On treatments (2, 4), where only amino acids were used or in addition in combination with sulphur and boron, the increase in glucosinolate concentration (GLS) was the largest. Regardless of the type of foliar fertilization used, the Monolit variety contained the lowest concentration of these compounds. The content of glucosinolates in rapeseeds of the studied cultivars varied during the years of the experiment. Studies have shown that the value of this feature increased with the growth of water stress occurring before harvest.

Morphologically and physiologically diverse fruits of two Lepidium species differ in allocation of glucosinolates into immature and mature seed and pericarp

The morphology and physiology of diaspores play crucial roles in determining the fate of seeds in unpredictable habitats. In some genera of the Brassicaceae different types of diaspores can be found. Lepidium appelianum produces non-dormant seeds within indehiscent fruits while in L. campestre dormant seeds are released from dehiscent fruits. These different diaspore types offer an excellent model system to analyse the allocation of relevant defence compounds into different tissues, which may maximise diaspore fitness. Total glucosinolate concentration and composition were analysed in immature and mature seeds and pericarps of L. appelianum and L. campestre using high-performance liquid chromatography. Moreover, transgenic RNAi L. campestre lines were used for comparison that produce indehiscent fruits due to silencing of LcINDEHISCENCE, the INDEHISCENCE ortholog of L. campestre. Total glucosinolate concentrations were lower in green compared to mature seeds in all studied Lepidium species and transgenic lines. In contrast, indehiscent fruits of L. appelianum maintained their total glucosinolate concentration in mature pericarps compared to green ones, while in dehiscent L. campestre and in indehiscent RNAi-LcIND L. campestre a significant decrease in total glucosinolate concentrations from green to mature pericarps could be detected. Regarding the distribution of glucosinolate classes, high concentrations of 4-methoxyindol-3-ylmethyl glucosinolate were found in mature seeds of L. appelianum, while no indole glucosinolates were detected in mature diaspores of L. campestre. The diaspores of the latter species may rather depend on aliphatic and aromatic glucosinolates for long-term protection. The allocation patterns of glucosinolates correlate with the morpho-physiologically distinct fruits of L. appelianum and L. campestre and may be explained by the distinct dispersal strategies and the dormancy status of both species.

Value of hydroalcoholic treatment of rapeseed for oil extraction and protein enrichment

This study investigated alternative solvents: ethanol and isopropanol, to replace hexane and enhance the quality and value of oil and meal. Rapeseed oil extraction was carried out using ethanol (92 wt.% or 96 wt.%), isopropanol (84 wt.% or 88 wt.%) or hexane (as reference). Results show that hydroalcoholic extraction increased meal protein content by 13% compared to hexane extraction, but without significant influence of alcohol and water content. However, increasing water content improved glucosinolate extractability. Isopropanol 84 wt.% eliminated most glucosinolates from the seeds, decreasing glucosinolate concentration by 49–73% compared to meals extracted by the other alcohols.

Evaluating strategies to improve glucosinolate concentration and root yield of field-grown horseradish in a Mediterranean environment: preliminary results

Horseradish is grown for its enlarged taproot that is widely used as a dish condiment and as a source of horseradish peroxidase. Nowadays, the species is gaining great interest due to the richness in bioactive compounds that besides providing a high nutritional value are tested for innovative applications in different fields. Nevertheless, the effect of crop management on root yield and glucosinolates (GLS) biosynthesis is poorly documented. Aim of this study was to evaluate the root yield and GLS concentration of two field-grown horseradish accessions (Cor and Mon) grown with nitrogen (N) alone and both N and sulphur (S) (-N-S, +N-S and +N+S treatments) and harvested at different times [late autumn (LA), 2011 and 2012, early spring (ES), 2012]. Yield increased throughout the harvests up to 48% on average of the fertilised treatments and 25% in the unfertilised control. Conversely, root GLS concentration significantly declined in the unfertilised control throughout the harvests [from 7.6 in LA_2011 to 1.43 μmol/g dry matter (DM) in LA_2012] while it highly increased in plants grown with N alone and with both N and S by 46 and 98%, respectively, from LA_2011 to ES_2012 (up to 11.9 and 21.1 μmol/g DM, respectively); then it drastically decreased by 80% on average, in the next harvest. Among individual GLS, the concentration of sinigrin and nasturtin similarly varied as effect of the analysed factors, showing the highest values in Cor accession. The data show that although the level of GLS is highly dependent on genotype, fertilisation and harvesting date may play a primary role in determining the yield and GLS concentration in horseradish root.