Effect of post‐harvest treatments on the level of glucosinolates in broccoli

Broccoli is a very perishable vegetable with a high water content (around 88%) which leads to rapid dehydration and probably to an alteration in composition if conditions after harvest are not controlled. This study evaluates the glucosinolate pattern and glucosinolate levels in the principal and secondary inflorescences of fresh broccoli cv ‘Tokyodome’, and after being submitted to some situations which are likely to occur during or after harvest: room temperature (±20 °C) for 5 days, kept in the fridge at 4 °C for 5 days, and frozen after blanching. Another set of material was harvested 5 days later, simulating a post‐maturation stage, and analysed. The highest total glucosinolate content was found at commercial maturation with 20 888 and 20 355 µmoles kg⁻¹ DW in the principal and secondary inflorescences, respectively. Keeping the inflorescences at room temperature caused the most significant (P < 0.05) reductions in total and individual glucosinolates, except for 4‐hydroxyindol‐3‐ylmethyl‐, 2‐hydroxy‐2‐phenylethyl‐ and 2‐phenylethyl‐, when compared to the other situations. The highest levels (10 925 µmoles kg⁻¹ DW) of 4‐methylsulphinylbutyl‐, the precursor of the anti‐cancer isothiocyanate sulphoraphane, were found in the inflorescences freshly harvested at commercial stage. Refrigeration at 4 °C and freezing were shown to be the best preservation processes for maintaining high levels of these and other glucosinolates in contrast with the other situations. © 1999 Society of Chemical Industry     

Variation in the content of glucosinolates,hydroxycinnamic acids,carotenoids, total antioxidant capacity and low‐molecular‐weight carbohydrates in Brassica vegetables

Bioactive compounds were investigated in genotypes (cauliflower 10, white cabbage 10, curly kale 1) and plant parts of the three crops. The content of most of the major glucosinolates glucobrassicin, sinigrin and glucoiberin differed significantly between cultivars. Samples harvested in 2000 had higher amounts of several glucosinolates than samples from 1999. Within cauliflower the buds of the floret had 1.5 to 2.5‐fold higher concentration of glucobrassicin and 4‐methoxyglucobrassicin than the stalk. In white cabbage several glucosinolates had their highest content in the outer leaves (up to 2‐fold higher). Upper leaves of curly kale contained 5‐fold more of total glucosinolates than lower leaves. Chlorogenic acid was the dominating hydroxycinnamate in curly kale, which also contained at least ten times more of carotenoids (mainly lutein) than white cabbage. Total antioxidant capacity (TAC) assayed with the FRAP method was 0.76 (0.06) µmol/g fw (mean (SD)) in water‐soluble and 0.32 (0.04) in water‐insoluble extracts of cauliflower which was 62–68% higher than in white cabbage. Curly kale contained 6.4 and 6.1 µmol/g fw TAC in water‐soluble and water‐insoluble extracts. TAC did not differ between plant parts. Progoitrin and 4‐hydroxyglucobrassicin were correlated to water‐soluble TAC in white cabbage, probably reflecting a variation in other compounds. Cauliflower contained less glucose, fructose and sorbitol but more sucrose than white cabbage. Curly kale had lower contents of glucose (～2 times), fructose (～4–5 times) and sucrose (20 and 36 times, respectively) than cauliflower and white cabbage, while inositol was only found in curly kale. Storage of white cabbage reduced the amount of sorbitol and sucrose. The study shows that cultivar, plant part and storage affect the content of bioactive compounds in Brassica vegetables. The variation between years, as in cauliflower, is due to environmental factors. Since the cultivar ranking order was rather stable for several components the data could provide a basis for the selection of cultivars optimised for valuable health components for fresh market consumption. Copyright © 2005 Society of Chemical Industry     

Phytochemical and Health‐Beneficial Progress of Turnip (Brassica rapa)

Despite the advancement of medical science, diseases are part‐and‐parcel of human life. Plants have provided humans with medicines since time immemorial, and are still one of the primary sources for drug discovery. Brassica rapa L., commonly known as turnip, is one of the world's oldest cultivated vegetables. Besides being an important vegetable and source of oil, turnip is also used as a traditional medicine for the treatment of headaches, chest complaints, rheumatisms, oedemas, gonorrhoea, syphilis, and rabies. Glucosinolates and isothiocyanates (mainly 2‐phenylethyl, 4‐pentenyl, and 3‐butenyl derivatives) are the main constituents of turnip with diverse bioactivities, especially for the protective effect against cancers. Besides, flavonoids, phenolics, indoles and volatiles are also concomitant in this plant. Pharmacological investigation on turnip revealed the antitumor, antihypertensive, antidiabetic, antioxidant, antiinflammatory, hepatoprotective, and nephroprotective effects. The anticancer property was found to be the most promising biological activity of turnip with 2‐phenylethyl isothiocyanate, phenylpropionitrile, brassicaphenanthrene A, 6‐paradol, and trans‐6‐shogaol as the major active constituents. Flavonoids and phenolics with high free radical scavenging activity should be corresponding to the antioxidant effects. Arvelexin, an indole derivative in turnip, was reported with various effects involving antiinflamatory, antihypertensive and hypolipidemic potency. In spite of many studies concerning either the chemical constituents or the biological activities of turnip, only a few cases disclosed the active ingredients responsible for diverse bioactivities. This review summarizes the research progress on the chemistry and health‐benefits of turnip over the past 20 years to provide a reference for the further investigation.     

Exploring new potential health‐promoting vegetables: glucosinolates and sensory attributes of rocket salads and related Diplotaxis and Eruca species

BACKGROUND: Rocket salads (Diplotaxis tenuifolia and Eruca vesicaria) are presently highly appreciated salad vegetables. Related species are consumed as food plants in several regions, and may contribute to differentiation in the fresh food supply chain. Glucosinolates are well‐known healthy phytochemicals and responsible for positive and negative sensory properties of edible Brassicaceae. To investigate the potential for exploitation of new crops, Diplotaxis and Eruca germplasm was subject to sensory evaluation and glucosinolate analysis. RESULTS: Typical rocket salad flavour and pungency were perceived as positive sensory traits. Bitter, and especially herbaceous notes, characterised the groups of less accepted accessions. The groups classified as significantly unpleasant were characterised by high glucosinolate content, with either sinigrin (strong perceived pungency, flavour and several other additional sensory notes), or sinalbin/gluconapin (strong herbaceous note, low flavour perceived), as the dominant components. CONCLUSIONS: Low glucosinolate content, and a composition rich in recognised health‐promoting components (glucoerucin, glucoraphanin) were associated with higher acceptance. In relation to food uses, moderate glucosinolate content and high acceptance may be a better option to enhance the intake of healthy phytochemicals than high glucosinolates and potential rejection. High glucosinolate types may find better perspectives in the field of food integrators. Copyright © 2009 Society of Chemical Industry     

Indoleacetonitriles—thermal degradation products of indole glucosinolates in commercial rapeseed (Brassica napus) meal

Commercial low-glucosinolate rapeseed (Brassica napus L) meal (LG RSM) was extracted with dichloromethane and subjected to chromatography on Sephadex LH-20 to isolate indole-containing compounds which were detected using TLC. Thin layer chromatography of dichloromethane extracts of various heat-treated preparations of defatted low-glucosinolate rapeseed cv Westar was also used to establish the origin of the major indole derivative. One of the minor components was identified as 3-indoleacetonitrile (IAN) based on comparisons of GLC retention times and mass spectral data with authentic IAN. The major indole derivative was identified as 4-hydroxy-3-indoleacetonitrile by comparison of mass spectral data with that for IAN and by establishing its precursor as 4-hydroxy-3-indolylmethylglucosinolate.     

Protein content determination in Brassica oleracea species using FT‐NIR technique and PLS regression

Six fresh and one frozen vegetable cultivar groups possessing remarkably different morphology from the same Brassica oleracea species, including broccoli, Brussels sprouts, curly cabbage, white cabbage, red cabbage, cauliflower and white kohlrabi, were chosen to set up a Fourier transform near‐infrared spectroscopy (FT‐NIR)‐based method for the quantification of protein content. Sample preparation was based on lyophilisation and homogenisation. Calibration was set up with the help of the Kjeldahl method for the quantification of protein content in the range of 12.9–32.5 m/m%. Calibration model was developed using the spectral regions 1136–1334 and 1639–1836 nm, with partial least squares regression. This model was checked by cross‐validation. The performance of the final FT‐NIR estimation model was evaluated by root mean square of cross‐validation, root‐mean‐square error of estimation and the determination coefficient (R²). The final estimation function for the protein determination was characterised with the predictive error of 0.76 m/m% and R² value of 98.81.     

Relationship between free amino acids and glucosinolates in primary and secondary inflorescences of 11 broccoli (Brassica oleracea L var italica) cultivars grown in early and late seasons

Amino acids have been identified as the precursors of a class of secondary plant metabolites, the glucosinolates, but there is no report on the relationship between the two in vivo. In this work we have investigated the relationship between free amino acids and glucosinolates in 11 broccoli cultivars grown in early (April–July) and late (August–January) seasons. Free amino acids and glucosinolates were quantified by HPLC in primary and secondary inflorescences at maturity stage. Analysis of the data revealed that no significant correlation exists between free amino acids and glucosinolates, suggesting that the precursors of these compounds might be used during the first step of the biosynthetic process to form intermediates, the aldoximes and thiohydroximates, which will then be used in the second stage of the biosynthesis to form, apart from glucosinolates, other secondary plant metabolites. © 2001 Society of Chemical Industry     

Effect of nitrogen and sulfur fertilization on glucosinolates in the leaves and roots of broccoli sprouts (Brassica oleracea var. italica)

Broccoli (Brassica oleracea L. var. italica cv. Marathon) sprouts are a rich source of glucosinolates, particularly 4‐methylsulfinylbutyl glucosinolate (glucoraphanin), the precursor of the chemoprotective isothiocyanate, sulforaphane. Sulfur and nitrogen fertilization have been shown to influence the pattern and levels of glucosinolates in mature broccoli, but little information is available on the fertilization of sprouts, a transient stage of broccoli growth, which have been recommended for salads. Therefore, an experiment was set up to evaluate the effect of N and S fertilization on the glucosinolate content of the aerial part and roots of broccoli sprouts. Nitrogen was tested at 0, 45.5, 91.0 mg L^?1 and sulfur at 0, 14.6 and 29.2 mg L^?1. The results showed that total glucosinolates in the aerial part were significantly higher (P < 0.001) than in the roots. The major glucosinolates in the aerial part were 4‐methylsulfinylbutyl and 3‐methylsulfinylpropyl whereas in the roots they were 2‐phenylethyl and 4‐methylthiobutyl. Fertilization of broccoli sprouts had a significant (P < 0.001) detrimental effect on the levels of aliphatic glucosinolates whereas the opposite was noted for indole and aromatic glucosinolates, for some of the fertilization combinations tested. Overall, the results indicate that broccoli sprouts do not benefit from fertilization. Copyright © 2006 Society of Chemical Industry     

Urea treatment of whole‐crop triticale at four growth stages: effects on chemical composition and on in vitro digestibility of cell wall

The objective of this study was to evaluate the preservative and upgrading potential of urea added to whole‐crop triticale. Triticale, harvested at different growth stages according to Feekes' scale (10.51, 10.54, 11.1 and 11.2), was ensiled with four levels of urea (0, 30, 60 and 90 g kg^?1 dry matter (DM)) and stored in plastic bags for 60 days. Data were analysed as a factorial design with growth stage and urea level as the main factors. Urea was extensively hydrolysed (more than 90% of added urea). Urea breakdown was not affected by urea level (P > 0.05) but decreased significantly with growth stage (P < 0.001). Microbial activity measured by pH, volatile fatty acid production and total non‐structural carbohydrate concentration was significantly reduced by the urea level. Urea treatment significantly (P < 0.001) increased water‐soluble and ammonium nitrogen; more than 85% of the added nitrogen was retained. Application of urea at a rate of 60 and 90 g kg^?1 DM significantly (P < 0.05) reduced the neutral detergent fibre (NDF) content and increased (P < 0.05) the NDF and acid detergent fibre in vitro digestibility. Whole‐crop triticale harvested at later growth stages (approximately 60% DM) can be effectively preserved and upgraded by ensiling with 60–90 g urea kg^?1 DM. Copyright © 2006 Society of Chemical Industry     

Evaluating potential applications of indigenous yeasts and their β‐glucosidases

The potential applications of wild yeast strains with β‐glucosidase activity were investigated by assaying their enzymatic production under simulated oenological conditions, coupled with the exploration of the potential applications of the β‐glucosidases by studying the enzymatic activity and stability under similar oenological conditions. The assay of enzymatic locations revealed that the β‐glucosidase activities from these wild strains occurred in the extracellular fraction, and in whole and permeabilized cells. The effects of different oenological factors on β‐glucosidase production indicated that the F6 Trichosporon asahii strain had higher β‐glucosidase production than the other strains under low pH conditions. However, the F35 Hanseniaspora uvarum strain and the F30 Saccharomyces cerevisiae strain showed higher β‐glucosidase production under high‐sugar conditions. Furthermore, the influence of oenological factors on the activity and stability of the β‐glucosidases revealed that the enzyme from the F6 T. asahii strain had a stronger low‐pH‐value resistance than the other yeast β‐glucosidases. These results suggest that the F35 H. uvarum, F30 S. cerevisiae and the F6 T. asahii β‐glucosidases may have some potentially applicable values in the fermentation industry. Copyright © 2015 The Institute of Brewing & Distilling     

Rice protein concentrate partially replaces dried whey in the diet for early‐weaned piglets and improves their growth performance

BACKGROUND: Recently, rice protein concentrate (RPC), a much cheaper source of dietary protein, has become commercially available for use in the feed industry. Importantly, dietary supplementation with RPC can increase feed intake by early‐weaned pigs. The objective of this study was to determine whether RPC can replace milk protein in the diet for early‐weaned pigs. RESULTS: Neither average daily gain (ADG), average daily feed intake (ADFI), nor the feed/gain ratio differed among the treatment groups in weeks 1 and 2. In week 3, the addition of 5 or 10% RPC to diets increased (P < 0.05) ADFI and ADG of pigs compared to those in the control group fed a 60% dried whey diet. During the entire 21‐day trial, ADFI and ADG were greater (P < 0.05) in pigs fed the 5 and 10% RCP diets than in pigs fed the 60% dried whey and 15% RCP diets. There were no differences in the serum concentrations of growth hormone on days 14 and 21, serum concentrations of insulin growth factor‐I (IGF‐I) on day 14, or IGF‐I gene expression in liver and skeletal muscle on days 14 and 21 among the dietary treatments. Serum concentrations of IGF‐I in pigs fed the 5, 10 and 15% RPC diets were greater than those in pigs fed the 60% dried whey diet. CONCLUSION: Findings indicate that up to 10% RPC can be used to replace dried whey in the diet for 7‐ to 21‐day‐old weaned piglets and can improve their growth performance. Copyright © 2008 Society of Chemical Industry