Blanching impact on pigments, glucosinolates, and phenolics of dehydrated broccoli by-products

Development of supercritical technology to obtain improved functional dietary fiber for the valorization of broccoli by-product

BACKGROUND

This research aimed to enhance the functional value of dietary fiber from broccoli leaves using supercritical fluid technology. By optimizing pressure, temperature, and time parameters through response surface methodology, the study sought to improve the bioactive properties of the fiber and develop a predictive model for its chemical composition and functional properties.

RESULTS

Structural analysis indicated that modified samples had a higher concentration of oligosaccharides than control samples did, with significant increases in galacturonic acid and neutral sugars after supercritical fluid technology treatment, highlighting enhanced pectin release due to cell wall degradation. Functional properties, such as water solubility, glucose absorption capacity, and antioxidant activity, improved significantly under optimized conditions (191 bar, 40 °C, 1 h). Multivariate analysis confirmed the effectiveness of supercritical fluid technology in enhancing the dietary fiber properties, achieving a global desirability value of 0.805.

CONCLUSION

These results underscore the potential of supercritical technology for valorizing broccoli leaf by-products, enhancing their health-promoting characteristics and functional applications in the food industry. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Enhancing the formation of functional glucosinolate degradation products in fermented broccoli stalk by-product with lactic acid bacteria

Broccoli stalk by-product (BsBP) is rich in glucosinolates (GSLs). Its fermentation process is generally characterized by the degradation of GSLs and formation of bioactive isothiocyanates (ITCs), in which lactic acid bacteria (LAB) play an important role. The GSLs-degrading capacity of 61 LAB strains was investigated in vitro. Lacticaseibacillus paracasei YC5, Pediococcus pentosaceus RBHZ36, and Lactiplantibacillus plantarum ND1, with high potential to transform GSLs into ITCs, were screened. The functional GSL degradation products (total content of sulforaphane, indol-3-carbinol, and ascorbigen) increased 22.0-33.5 % compared to natural fermentation after 24 h when BsBP was fermented by the three screened strains in pure culture. LAB fermentation also helped to increase the quantity of indolic GSL degradation products in BsBP brine, suggesting that LAB fermentation promoted BsBP GSLs transformation into bioactive ITCs. The proposed use of the LAB strains characterized in this study provided a fermented BsBP and brine with high profile of functional GSL degradation products.

Comprehensive Analysis of Bioactive Compounds, Functional Properties, and Applications of Broccoli By-Products

Broccoli by-products, traditionally considered inedible, possess a comprehensive nutritional and functional profile. These by-products are abundant in glucosinolates, particularly glucoraphanin, and sulforaphane, an isothiocyanate renowned for its potent antioxidant and anticarcinogenic properties. Broccoli leaves are a significant source of phenolic compounds, including kaempferol and quercetin, as well as pigments, vitamins, and essential minerals. Additionally, they contain proteins, essential amino acids, lipids, and carbohydrates, with the leaves exhibiting the highest protein content among the by-products. Processing techniques such as ultrasound-assisted extraction and freeze-drying are crucial for maximizing the concentration and efficacy of these bioactive compounds. Advanced analytical methods, such as high-performance liquid chromatography-mass spectrometry (HPLC-MS), have enabled precise characterization of these bioactives. Broccoli by-products have diverse applications in the food industry, enhancing the nutritional quality of food products and serving as natural substitutes for synthetic additives. Their antioxidant, antimicrobial, and anti-inflammatory properties not only contribute to health promotion but also support sustainability by reducing agricultural waste and promoting a circular economy, thereby underscoring the value of these often underutilized components.

Comprehensive Assessment of Anti-Inflammatory, Antiproliferative and Neuroprotective Properties of Cauliflower after Dehydration by Different Drying Methods

Cauliflower (Brassica oleraceae L. var. Botrytis Linnaeus) has various health benefits due to its rich bioactive compound content. However, this fresh vegetable faces challenges related to its perishability and short shelf life. This study explores the effect of five drying methods, namely vacuum drying (VD), convective drying (CD), infrared drying (IRD), low-temperature vacuum drying (LTVD) and vacuum freeze-drying (VFD), on the bioactive compounds and health-promoting properties of cauliflower. Analyses of amino acids, hydroxycinnamic acid and its derivatives, glucosinolates, and isothiocyanates, as well as evaluations of their anti-inflammatory, antiproliferative, and neuroprotective properties, were conducted based on these five drying methods. The results revealed that samples treated with VFD and IRD had a higher content of amino acids involved in GSL anabolism. Moreover, VFD samples retained hydroxycinnamic acid derivatives and glucosinolates to a greater extent than other methods. Nonetheless, the CD and VD samples exhibited higher antiproliferative and neuroprotective effects, which were correlated with their high sulforaphane content. Overall, considering the retention of most bioactive compounds from cauliflower and the topical inflammation amelioration induced in mice, VFD emerges as a more satisfactory option.

Processing and preservation technologies to enhance indigenous food sovereignty, nutrition security and health equity in North America

Indigenous foods are carriers of traditional native North American food culture and living philosophy. They are featured by the wide varieties in fresh and processed forms, richness in nutrition, flavor, health benefits and diversity in origins, but are usually misunderstood or underrepresented in the modern food systems. Conventional processing and cooking methods are sometimes labor-intensive, less efficient and lack science-based guidelines to prevent unseen safety risks and food loss. Global and regional climate change have caused additional challenges to conventional cooking/processing, and increased native communities' reliance on externally produced foods, which have resulted in increasing nutritional unbalance and prevalence of diet-related health issues. Current and emerging technologies, such as storage and packaging, drying, safety processing, canning, pickling, and fermentation, which treat foods under optimized conditions to improve the safety and extend the shelf-life, are increasingly used in current food systems. Therefore, exploring these technologies for indigenous foods offers opportunities to better preserve their nutrition, safety, and accessibility, and is critical for the sovereignty and independence of indigenous food systems, and sustainability of indigenous food culture. This mini-review focuses on identifying adoptable processing and preservation technologies for selected traditional indigenous foods in North America, summarizing education, extension, and outreach resources and discussing the current challenges and future needs critical to expanding knowledge about indigenous foods and improving food sovereignty, nutrition security, and health equity.

Effects of pretreatment and freezing storage on the bioactive components and antioxidant activity of two kinds of celery after postharvest

Celery is well liked for it medicinal functions and nutritive value. However, fresh celery is not resistant to storage, severely limiting its supply time and marketing region. In this study, the effects of pretreatment and freezing storage on the nutritional quality of two kinds of celery (Chinese celery cultivar 'Lvlin Huangxinqin' and Western celery cultivar 'Jinnan Shiqin') after postharvest were investigated. Under all treatment combinations, 120 s blanching at 60 °C and 75 s blanching at 75 °C were the most effective pretreatments for 'Lvlin Huangxinqin' and 'Jinnan Shiqin', respectively. These two pretreatments combinations effectively delayed the decline of chlorophyll and fiber content, and maintained the level of carotenoids, soluble protein, total sugars, DPPH radical scavenging, total phenols, and vitamin C during freezing storage. These findings suggest that blanching and quick-freezing treatments are beneficial to maintain the nutritional quality of two kinds of celery, which have important reference significance for the postharvest processing of celery.

Impact of Fermentation and Pasteurization on the Physico-Chemical and Phytochemical Composition of Opuntia ficus-indica Juices

Opuntia ficus-indica fruits are a source of valuable compounds, presenting a high nutritional value and several health benefits. However, due to its low shelf life and increased production, there are considerable post-harvest losses of this cactus fruit. So, ways need to be found to drain the increased production of this fruit that is being wasted. The chemical composition of prickly pear makes it an appealing substrate for fermentation. This study investigates the production of fermented beverages produced from Opuntia ficus-indica cv 'Rossa' and evaluates the effects of different fermentation times (18 and 42 h) and post-fermentation pasteurization by high-pressure (500 MPa for 10 min) and temperature (71.1 °C for 30 s) on the physico-chemical and biological characteristics of the produced beverages. According to the results, the beverage produced from 48 h of fermentation has an alcohol content value of 4.90 ± 0.08% (v/v) and a pH of 3.91 ± 0.03. These values contribute to an extended shelf life and improved organoleptic characteristics compared to the sample fermented for 18 h. Additionally, the longer fermentation resulted in 50% fewer total soluble solids, 90% less turbidity, and lower pH when compared to the sample fermented for 18 h. Moreover, overall, high-pressure processing demonstrates better retention of "fresh-like" characteristics, along with higher levels of phytochemical compounds and antioxidant capacity, similar to those observed in the juice for SO^•- and NO^•-scavenging abilities.

Chlorophylls as Natural Bioactive Compounds Existing in Food By-Products: A Critical Review

Chlorophylls are a group of naturally occurring pigments that are responsible for the green color in plants. This pigment group could have numerous health benefits due to its high antioxidant activity, including anti-inflammatory, anti-cancer, and anti-obesity properties. Many food by-products contain a high level of chlorophyll content. These by-products are discarded and considered environmental pollutants if not used as a source of bioactive compounds. The recovery of chlorophylls from food by-products is an interesting approach for increasing the sustainability of food production. This paper provides insight into the properties of chlorophylls and the effect of different treatments on their stability, and then reviews the latest research on the extraction of chlorophylls from a sustainable perspective.

Hot-air-assisted radio frequency blanching of broccoli: heating uniformity, physicochemical parameters, bioactive compounds, and microstructure

BACKGROUND

Vegetables are often blanched before drying. The hot-water blanching (HWB) of broccoli reduces quality and is environmentally harmful. In this work, hot-air-assisted radio frequency heating blanching (HA-RFB) of broccoli was developed for use before further drying processes. Blanching sufficiency, heating uniformity, and heating rate during HA-RFB were investigated to improve the product's physicochemical properties and texture. Suitable heating conditions were achieved when HA-RFB was applied with hot air at 70 °C, with an electrode gap of 10.7 cm, using a cylindrical container for the broccoli.

RESULTS

Under these conditions, the relative peroxidase activity in broccoli decreased to 3.26% within 117 s, with 13.45% of weight loss. In comparison with HWB broccoli, the products blanched by HA-RFB preserved their texture, bioactive compounds, and microstructure better. The ascorbic acid, sulforaphane, and total glucosinolate content in HA-RFB products were 251.1%, 131.9% and 36.7% higher than those in HWB broccoli, and HA-RFB treatment led to a greater weight loss (13.45 ± 0.50%) than HWB (8.70 ± 1.70%), which is very helpful for the subsequent drying process.

CONCLUSION

This study demonstrated that HA-RFB could be a promising substitute for HWB to blanch broccoli and other flower vegetables, especially as a pretreatment in the drying process. © 2023 Society of Chemical Industry.

Structure-function relationships of pectic polysaccharides from broccoli by-products with in vitro B lymphocyte stimulatory activity

To study structure-function relationships of pectic polysaccharides with their immunostimulatory activity, broccoli by-products were used. Pectic polysaccharides composed by 64 mol% uronic acids, 18 mol% Ara, and 10 mol% Gal, obtained by hot water extraction, activated B lymphocytes in vitro (25-250 μg/mL). To disclose active structural features, combinations of ethanol and chromatographic fractionation and modification of the polysaccharides were performed. Polysaccharides insoluble in 80 % ethanol (Et80) showed higher immunostimulatory activity than the pristine mixture, which was independent of molecular weight range (12-400 kDa) and removal of terminal or short Ara side chains. Chemical sulfation did not promote B lymphocyte activation. However, the action of pectin methylesterase and endo-polygalacturonase on hot water extracted polysaccharides produced an acidic fraction with a high immunostimulatory activity. The de-esterified homogalacturonan region seem to be an important core to confer pectic polysaccharides immunostimulatory activity. Therefore, agri-food by-products are a source of pectic polysaccharide functional food ingredients.

Genus Brassica By-Products Revalorization with Green Technologies to Fortify Innovative Foods: A Scoping Review

Food losses and waste reduction are a worldwide challenge involving governments, researchers, and food industries. Therefore, by-product revalorization and the use of key extracted biocompounds to fortify innovative foods seems an interesting challenge to afford. The aim of this review is to evaluate and elucidate the scientific evidence on the use of green technologies to extract bioactive compounds from Brassica by-products with potential application in developing new foods. Scopus was used to search for indexed studies in JCR-ISI journals, while books, reviews, and non-indexed JCR journals were excluded. Broccoli, kale, cauliflower, cabbage, mustard, and radish, among others, have been deeply reviewed. Ultrasound and microwave-assisted extraction have been mostly used, but there are relevant studies using enzymes, supercritical fluids, ultrafiltration, or pressurized liquids that report a great extraction effectiveness and efficiency. However, predictive models must be developed to optimize the extraction procedures. Extracted biocompounds can be used, free or encapsulated, to develop, reformulate, and/or fortify new foods as a good tool to enhance healthiness while preserving their quality (nutritional, functional, and sensory) and safety. In the age of recycling and energy saving, more studies must evaluate the efficiency of the processes, the cost, and the environmental impact leading to the production of new foods and the sustainable extraction of phytochemicals.

Effect of High-Pressure and Thermal Pasteurization on Microbial and Physico-Chemical Properties of Opuntia ficus-indica Juices

Opuntia fruits are recognized for their richness in nutrients and in bioactive compounds, being also highly appreciated by consumers as a juice. Nevertheless, without further processing, prickly pear juices have a short shelf-life, hampering their commercial use. In this work, thermal (TP) and high-pressure (HPP) pasteurization were applied to juices from Opuntia ficus-indica cultivars ‘Rossa’, ‘Gialla’, and ‘Bianca’ to understand the impact of those methods on the microbial safety, physico-chemical properties, and the nutritional content of the samples, over storage at 4 °C. In general, thermal pasteurization at 71.1 °C for 30 s increased the shelf-life by 22 days, and high-pressure pasteurization at 500 MPa for 10 min increased the shelf-life by 52 days with regard to microbial growth as well as maintenance of physical-chemical characteristics. The application of these two pasteurization methods delayed changes in the physico-chemical characteristics of the juices, with a more pronounced effect on the titratable acidity, °Brix and browning. For the same periods of time, the application of pasteurization methods decreased the variation in these quality parameters by around 75%. Similarly, these methods were shown to have the same effect on the polyphenolic concentration as well as the antioxidant activity of the juices. In particular, HPP was more efficient in preventing a decrease in °Brix and increase in titratable acidity, which normally negatively affect the flavor of the juices.

Oil matrix modulates the bioaccessibility of polyphenols: a study of salad dressing formulation with industrial broccoli by-products and lemon juice

BACKGROUND

The potential health-promoting effects of polyphenols depend considerably on their bioaccessibility, which is affected by the presence of other nutrients in the diet, including lipids. In this study, several salad dressing formulations were prepared using industrial broccoli by-product powder (BBP), lemon juice (LJ), and three different sources of oils (olive oil, hazelnut oil and sunflower oil) to both valorize polyphenol-rich industrial discards and also to investigate polyphenol bioaccessibility. The changes in the bioaccessibility of polyphenols from BBP and LJ were determined using the standardized in vitro digestion model.

RESULTS

Four groups of polyphenols (hydroxycinnamic acids, flavonols, flavones, and flavonones) were detected in BBP and LJ. The bioaccessibility of hydroxycinnamic acids and flavonols from BBP increased significantly in the presence of LJ and oils (0.3- to 5.8-fold), whereas there was no significant difference between formulations containing different oil types. On the other hand, the bioaccessibility of phenolic acids from LJ did not change notably after co-ingestion with BBP and oils, whereas flavonoids, including vicenin-2 and hesperidin, were found to be significantly more bioaccessible when LJ was co-ingested with BBP and oils (0.8- to 1.4-fold) (P < 0.05).

CONCLUSION

Overall, the current study highlighted that the bioaccessibility of polyphenols from BBP and LJ was modulated in the presence of an oil matrix. © 2022 Society of Chemical Industry.

The glucosinolate profiles of Brassicaceae vegetables responded differently to quick-freezing and drying methods

Glucosinolates (GLS) are bioactive compounds found in Brassicaceae vegetables. Industrial food processing treatments, such as blanching, quick-freezing (QF), vacuum freeze-drying (VFD), vacuum-drying (VD) and oven-drying (OD), significantly affect the degradation and ingestion of GLS. Here, the effects of these treatments, followed by boiling, on the GLS content and mimicking ingestion level of isothiocyanate from Brassicaceae vegetables (broccoli, cauliflower, white and red cabbages, Chinese and baby cabbages, white and red radish roots) were investigated. The results showed that blanching-QF maintained or increased the GLS content as well as preserved the ingestion level of isothiocyanate, an optimum treatment for GLS preservation. Blanching-VFD was recommended for these vegetables, while blanching-VD and blanching-OD caused relatively high GLS losses and low isothiocyanate production. Additionally, stabilities of individual GLS during processing rely on their chemical structures and species. Generally, aliphatic GLS from Brassicaceae showed lower loss than indole GLS, indicating differences in their stabilities during processing.

Maximization of Sulforaphane Content in Broccoli Sprouts by Blanching

Broccoli sprouts are a recognized source of health-promoting compounds, such as glucosinolates, glucoraphanin, and sulforaphane (SFN). Maximization of SFN content can be achieved by technological processing. We investigated the effect of blanching conditions to determine the optimal treatment that maximizes sulforaphane content in broccoli sprouts. Broccoli seeds (cv. Traditional) grown under controlled conditions were harvested after 11 days from germination and subjected to different blanching conditions based on a central composite design with temperature and time as experimental factors. Results were analyzed by ANOVA followed by a Tukey test. The optimum conditions were identified through response surface methodology. Blanching increased sulforaphane content compared with untreated sprouts, agreeing with a decrease in total glucosinolates and glucoraphanin content. Temperature significantly affected SFN content. Higher temperatures and shorter immersion times favor glucoraphanin hydrolysis, thus increasing SFN content. The optimum conditions were blanching at 61 °C for 4.8 min, resulting in 54.3 ± 0.20 µmol SFN/g dry weight, representing a 3.3-fold increase with respect to untreated sprouts. This is the highest SFN content reported for sprouts subjected to any treatment so far. The process described in this work may contribute to developing functional foods and nutraceuticals that provide sulforaphane as an active principle.

Novel Approaches for the Recovery of Natural Pigments with Potential Health Effects

The current increased industrial food production has led to a significant rise in the amount of food waste generated. These food wastes, especially fruit and vegetable byproducts, are good sources of natural pigments, such as anthocyanins, betalains, carotenoids, and chlorophylls, with both coloring and health-related properties. Therefore, recovery of natural pigments from food wastes is important for both economic and environmental reasons. Conventional methods that are used to extract natural pigments from food wastes are time-consuming, expensive, and unsustainable. In addition, natural pigments are sensitive to high temperatures and prolonged processing times that are applied during conventional treatments. In this sense, the present review provides an elucidation of the latest research on the extraction of pigments from the agri-food industry and how their consumption may improve human health.

A New Food Ingredient Rich in Bioaccessible (Poly)Phenols (and Glucosinolates) Obtained from Stabilized Broccoli Stalks

Broccoli (Brassica oleracea var. italica) stalks account for up to 35% of the broccoli harvest remains with the concomitant generation of unused waste that needs recovery to contribute to the sustainability of the system. However, due to its phytochemical composition, rich in bioactive (poly)phenols and glucosinolates, as well as other nutrients, the development of valorization alternatives as a source of functional ingredients must be considered. In this situation, the present work aims to develop/obtain a new ingredient rich in bioactive compounds from broccoli, stabilizing them and reducing their degradation to further guarantee a high bioaccessibility, which has also been studied. The phytochemical profile of lyophilized and thermally treated (low-temperature and descending gradient temperature treatments), together with the digested materials (simulated static in vitro digestion) were analysed by HPLC-PDA-ESI-MSn and UHPLC-3Q-MS/MS. Broccoli stalks and co-products were featured by containing phenolic compounds (mainly hydroxycinnamic acid derivatives and glycosylated flavonols) and glucosinolates. The highest content of organosulfur compounds corresponding to the cores of the broccoli stalks treated by applying a drying descendant temperature gradient (aliphatic 18.05 g/kg dw and indolic 1.61 g/kg dw, on average, while the breakdown products were more abundant in the bark ongoing low temperature drying 11.29 g/kg dw, on average). On the other hand, for phenolics, feruloylquinic, and sinapoylquinic acid derivatives of complete broccoli stalk and bark, were more abundant when applying low-temperature drying (14.48 and 28.22 g/kg dw, on average, respectively), while higher concentrations were found in the core treated with decreasing temperature gradients (9.99 and 26.26 g/kg dw, on average, respectively). When analysing the bioaccessibility of these compounds, it was found that low-temperature stabilization of the core samples provided the material with the highest content of bioactives including antioxidant phenolics (13.6 and 33.9 g/kg dw of feruloylquinic and sinapoylquinic acids, on average, respectively) and sulforaphane (4.1 g/kg dw, on average). These processing options enabled us to obtain a new product or ingredient rich in bioactive and bioaccessible compounds based on broccoli stalks with the potential for antioxidant and anti-inflammatory capacities of interest.

Effects of ultrasound, heat, ascorbic acid and CaCl2 treatments on color enhancement and flavor changes of freeze-dried carrots during the storage period

Discoloration and unpleasant flavor were observed in freeze-dried carrots (FDC) during shelf life. This study aimed to investigate the effects of thermal/non-thermal pre-treatments and storage temperatures on the color and flavor of FDC during the 120-day storage. Results showed that terpenes and sulfur-containing organics were the main volatiles sensitive to the 60 °C treatment (p < 0.05). Nonenzymatic browning of FDC happened during storage, which was significantly positively related to moisture content (r = 0.63) and water activity (r = 0.84), while negatively correlated with total carotenoid content (TCC, r = -0.62). However, redness (29.66%), chroma (16.59%) and TCC (3.40%) of FDC at 120-day (25 °C) was effectively improved after the combination treatment of ultrasound (40 kHz, 100 W, 10 min) and ascorbic acid (2%, w/v)-CaCl₂ (1%, w/v) solution (UAA-CaCl₂), showing that carrots pre-treated with UAA-CaCl₂ and preserved at 25 °C facilitated the FDC storage.

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.

Nutrient-Dense Shelf-Stable Vegetable Powders and Extruded Snacks Made from Carrots and Broccoli

Perishable fresh vegetables that do not meet cosmetic standards and by-products of processing are currently wasted. Broccoli and carrots were selected as model vegetables to demonstrate that they can be converted into nutrient-dense and shelf-stable food ingredients and formulated into convenient ready-to-eat snacks. Broccoli powder was a rich source of protein (30%) and dietary fibre (28%). Carrot powder had lower protein (6.5%) and dietary fibre content (24%) and was higher in sugar (47%) compared to broccoli powder (21%). Compared to the whole-vegetable powders, pomace powders were richer in fibre but had lower levels of total carbohydrates. There was a reduced expansion of extruded snacks with increasing levels of the vegetable component in the formulation. Processing and storage for 12 months at 25 °C or 40 °C resulted in changes in the measured soluble phenolic content. Changes during storage were dependent on the temperature and time. The changes may be in part due to the changes in the material properties of the matrix as a consequence of processing and storage, which affect extractability. The conversion of perishable vegetables and pomace into shelf-stable nutrient-dense food ingredients and products will reduce food loss and waste in the vegetable industry.

Discoloration investigations of freeze-dried carrot cylinders from physical structure and color-related chemical compositions

BACKGROUND

High carotenoid content always lead to a yellower/redder color in carrots, while a puzzling phenomenon still exists that freeze-dried carrots (FDC) have a higher carotenoid content but a lighter color compared with thermal-dried carrots. It seems that carotenoid is not the only main factor affecting sample color. Hence the discoloration characteristics of freeze-dried carrots were comprehensively analyzed from physical structure and color-related chemical composition profile.

RESULTS

Outcomes of low-field nuclear magnetic resonance and scanning electron microscopy showed that sublimation of immobilized water preserved the intact porous structure of FDC, which kept the volume shrinkage below 30% and led to less accumulations of color-related compositions. Besides, results of correlation and principal component analysis-X model proved that lutein and caffeic acid mainly affected a* value (r = 0.917) and b* value (r = 0.836) of FDC, respectively. Moreover, lipoxygenase indirectly affected sample color by degrading carotenoids, and the lutein content loss for fresh and blanching FDC was 41.56% and 47.14%, respectively.

CONCLUSIONS

The discoloration of FDC was significantly affected by both physical structure and color-related chemical compositions. © 2021 Society of Chemical Industry.

Stinging Nettles as Potential Food Additive: Effect of Drying Processes on Quality Characteristics of Leaf Powders

Stinging nettle (Urtica dioica L.) is a ubiquitous, multi-utility, and under-utilized crop with potential health benefits owing to its nutritional and bioactive components. The objective of the work is to produce powders by drying wild stinging nettle leaves as a storable, low-cost functional additive to be used in bakery and ready-to-cook products. Convective drying (CD) and freeze-drying (FD) were applied on unblanched (U) or blanched (B) leaves, which were then milled to nettle powders (NPs). The obtained NPs were evaluated for selected physicochemical (moisture, color), techno-functional (flow indices, hygroscopicity), and phytochemical (pigments, phenols) characteristics as well as mineral contents. Blanching improved mass transfer and reduced the oxidative degradation of pigments during drying, but it caused a loss of total phenols content, antioxidant activity, and potassium content. As for the drying method, CD resulted in better flow properties (i.e., Carr Index and Hausner Ratio), while FD retained better the color, pigments, magnesium content, phenolic, and antioxidant parameters. Overall, the evaluated processing methods resulted in different technological properties that can allow for better evaluation of NPs as a food additive or ingredient. Among the NPs, blanched and freeze-dried powders despite showing inferior technological properties can be recommended as more suitable ingredients targeted f or food enrichment owing to better retention of bio-active components.

Recent Trends in Pretreatment of Food before Freeze-Drying

Drying is among the most important processes and the most energy-consuming techniques in the food industry. Dried food has many applications and extended shelf life. Unlike the majority of conventional drying methods, lyophilization, also known as freeze-drying (FD), involves freezing the food, usually under low pressure, and removing water by ice sublimation. Freeze-dried materials are especially recommended for the production of spices, coffee, dried snacks from fruits and vegetables and food for military or space shuttles, as well as for the preparation of food powders and microencapsulation of food ingredients. Although the FD process allows obtaining dried products of the highest quality, it is very energy- and time consuming. Thus, different methods of pretreatment are used for not only accelerating the drying process but also retaining the physical properties and bioactive compounds in the lyophilized food. This article reviews the influence of various pretreatment methods such as size reduction, blanching, osmotic dehydration and application of pulsed electric field, high hydrostatic pressure or ultrasound on the physicochemical properties of freeze-dried food and drying rate.

Effect of Chlorophyll Hybrid Nanopigments from Broccoli Waste on Thermomechanical and Colour Behaviour of Polyester-Based Bionanocomposites

Natural dyes obtained from agro-food waste can be considered promising substitutes of synthetic dyes to be used in several applications. With this aim, in the present work, we studied the use of chlorophyll dye (CD) extracted from broccoli waste to obtain hybrid nanopigments based on calcined hydrotalcite (HT) and montmorillonite (MMT) nanoclays. The synthesized chlorophyll hybrid nanopigments (CDNPs), optimized by using statistical designed experiments, were melt-extruded with a polyester-based matrix (INZEA) at 7 wt% loading. Mechanical, thermal, structural, morphological and colour properties of the obtained bionanocomposites were evaluated. The obtained results evidenced that the maximum CD adsorption into HT was obtained when adding 5 wt% of surfactant (sodium dodecyl sulphate) without using any biomordant and coupling agent, while the optimal conditions for MMT were achieved without adding any of the studied modifiers. In both cases, an improvement in CD thermal stability was observed by its incorporation in the nanoclays, able to protect chlorophyll degradation. The addition of MMT to INZEA resulted in large ΔE* values compared to HT incorporation, showing bionanocomposite green/yellow tones as a consequence of the CDNPs addition. The results obtained by XRD and TEM revealed a partially intercalated/exfoliated structure for INZEA-based bionanocomposites, due to the presence of an inorganic filler in the formulation of the commercial product, which was also confirmed by TGA analysis. CDNPs showed a reinforcement effect due to the presence of the hybrid nanopigments and up to 26% improvement in Young's modulus compared to neat INZEA. Finally, the incorporation of CDNPs induced a decrease in thermal stability as well as limited effect in the melting/crystallization behaviour of the INZEA matrix. The obtained results showed the potential use of green natural dyes from broccoli wastes, adsorbed into nanoclays, for the development of naturally coloured bionanocomposites.

Effect of Drum-Drying Conditions on the Content of Bioactive Compounds of Broccoli Pulp

This work studied the effect of drum-rotation frequency, drum temperature, and water-to-pulp ratio in a double-drum drier on the content of sulforaphane, glucoraphanin, total phenolic compounds, ascorbic acid, and antioxidant activity of broccoli pulp through a multilevel factorial design with one replicate. Drum-drying conditions did not significantly affect sulforaphane content, unlike glucoraphanin, however the poor adherence of broccoli pulp resulted in a final product with undefined shape and heterogeneous color. On the other hand, antioxidant activity was unevenly affected by drying conditions; however, drum-rotation frequency affected it in the same way that phenolic compounds and ascorbic acid, showing a concordant behavior. The ascorbic acid content decreased significantly after drying, and it was highly dependent on the experimental factors, resulting in a regression model that explained 90% of its variability. Drum-rotation frequency of 5 Hz, drum temperature of 125 °C, and water-to-pulp ratio of 0.25 resulted in an apparent increase of sulforaphane and phenolic compounds content of 13.7% and 47.6%, respectively. Drum drying has great potential to fabricate dehydrated broccoli-based foods with functional properties. Besides, since drum drying has low investment and operation costs, it represents a very attractive option for the industrialization of broccoli derivatives.

Antimicrobial, antioxidant, volatile and phenolic profiles of cabbage-stalk and pineapple-crown flour revealed by GC-MS and UPLC-MSE

Unconventional parts of vegetables represent a rich source of health-promoting phytochemicals. The phenolic profile of cabbage-stalk flour (CSF), pineapple-crown flour (PCF), and their essential oils were characterized via UPLC-ESI-QTOF-MS^E and GC-FID/MS. Antimicrobial activity was tested against five strains, and antioxidant activities were determined in free and bound extracts. Globally, 177 phenolics were tentatively identified in PCF (major p-coumaric acid, ferulic acid, and 4-hydroxybenzaldehyde) and 56 in CSF (major chlorogenicacid, quercetin 3-O-glucuronide, and p-coumaric acid). PCF exhibited a distinguished profile (lignans, stilbenes) and antioxidant capacity, especially in bound extracts (1.3 g GAE.100 g^-1; 0.6 g catechin eq.100 g^-1; DPPH: 244.7; ABTS: 467.8; FRAP: 762.6 µg TE.g^-1, ORAC: 40.9 mg TE.g^-1). The main classes of volatile compounds were fatty acids, their esters, and terpenes in CSF (30) and PCF (41). A comprehensive metabolomic approach revealed CSF and PCF as a promising source of PC, showing great antioxidant and discrete antimicrobial activities.