Dietary-Fibre-Rich Fractions Isolated from Broccoli Stalks as a Potential Functional Ingredient with Phenolic Compounds and Glucosinolates

Abstract

The Brassica oleracea industry generates large amounts of by-products to which value could be added because of the characteristics of their composition. The aim was to extract different fibre fractions from broccoli stalks to obtain potential new added-value ingredients. Using an ethanol and water extraction procedure, two fibre-rich fractions (total fibre fraction, TFB, and insoluble fibre fraction, IFB) were obtained. These fractions were analysed to determine the nutritional, (poly)phenols and glucosinolates composition and physicochemical properties, comparing the results with those of freeze-dried broccoli stalks (DBS). Although TFB showed a higher content of total dietary fibre, IFB had the same content of insoluble dietary fibre as TFB (54%), better hydration properties, higher content of glucosinolates (100 mg/100 g d.w.) and (poly)phenols (74.7 mg/100 g d.w.). The prebiotic effect was evaluated in IFB and compared with DBS by in vitro fermentation with human faecal slurries. After 48 h, the short-chain fatty acid (SCFA) production was higher with IFB than with DBS because of the greater presence of both uronic acids, the main component of pectin, and (poly)phenols. These results reveal that novel fibre-rich ingredients—with antioxidant, technological and physiological effects—could be obtained from broccoli stalks by using green extraction methods.

Interaction between Dietary Fibre and Bioactive Compounds in Plant By-Products: Impact on Bioaccessibility and Bioavailability

“…The information in the literature regarding whether glucosinolates can be found bound to fibre or not is inconclusive. In this regard, in a previous study that we performed with broccoli stalks, we only found extractable glucosinolates, agreeing with the results observed by other authors [ 30 , 104 ]. However, glucosinolates are found in the sections of fibre obtained after extraction, as glucosinolates remain trapped in the vegetable structures, with glucoraphanin being the main one identified in broccoli by-products [ 105 ].…”

“…Other authors have reported that grape, tomato pomace, and red corn cob contain significant concentrations of gallic acid, rutin, epicatechin, and apigenin [ 25 , 33 ]. Relevant contents of carotenoids have also been reported in orange, mango, carrot, and tomato by-products [ 25 , 34 ], while glucosinolates have been reported in broccoli stalks [ 30 ].…”

“…Cellulose is the most abundant biopolymer in nature and is found in high amounts in stems, straw, and peels, constituting 42% of banana stems, 51% of maize straw, and 41% and 39%, respectively, of onion and oat peels [ 59 ]. Cellulose has also been found in high proportions in citrus peel, grapefruit wastes, broccoli stalks, and tomato peel fibre (34%, 27%, 19%, and 13%, respectively) [ 25 , 30 , 60 ]. Hemicellulose is the second most abundant component of lignocellulosic biomass, after cellulose [ 61 , 62 ], and is found in blackcurrant pomace (constituting 25%), chokeberry (34%), cherry (11%), citrus peel (10%), and grapefruit waste (6%) [ 60 , 63 ].…”

“…In addition to the Brassicaceae family, other edible dicotyledons, such as capers, papaya, and moringa, contain glucosinolates [ 95 ]. Different glucosinolates have been identified in Brassicaceae by-products, such as broccoli stalks, mustard leaves, and winter rapeseed leaves and stems [ 30 , 96 , 97 ].…”

The synergistic ramification of insoluble dietary fiber and associated non-extractable polyphenols on gut microbial population escorting alleviation of lifestyle diseases

“…The insoluble dietary fibre fraction was nutritionally important with high content of polyphenols, glucosinolates with high prebiotic score. Environment friendly by-product may be used in food and pharmaceutical industry ( Núñez-Gómez et al, 2022 ).…”