Evaluation of the antioxidant activity of asparagus,broccoli and their juices

Antioxidant activity of asparagus, broccoli and their juices was evaluated using 2,2′-diphenyl-l-picrylhydrazyl (DPPH), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and β-carotene bleaching assays. Asparagus showed greater antioxidant activity than broccoli. Asparagus juice also had greater antioxidant activity than broccoli juice. Methanol and acetone extracts of asparagus and broccoli had significantly greater antioxidant activity than their water extracts. Asparagus and broccoli extracts, as well as their juices, showed no significant difference in total phenolics content. However, asparagus contained more flavonoids than broccoli. The antioxidant activity of asparagus and broccoli extracts demonstrated a linear relationship with their flavonoid content.     

The effects of cooking method on selected quality traits of broccoli and green asparagus

Broccoli and green asparagus were cooked using boiling water, steam, microwave oven and combi oven with overheated steam and combination of hot air with overheated steam (only broccoli). Vegetables were analysed for chlorophylls a and b, carotenoids, total polyphenols, antioxidant activity, colour parameters and sensory properties. Cooking in the combi oven with overheated steam was an effective method to achieve the highest levels of polyphenols and antioxidant activity, but it negatively influenced the contents of chlorophylls in both vegetables and carotenoids in asparagus. Boiling and cooking in the combi oven with overheated steam or hot air and steam ensured the best and comparable sensory properties of broccoli. Asparagus showed a lower susceptibility to heat treatments than broccoli as none of the treatments applied caused significant differences in colour redness and yellowness, polyphenol content and sensory properties of this vegetable.     

Loss of rutin and antioxidant activity of asparagus juice caused by a pectolytic enzyme preparation from Aspergillus niger

We found that a commercial pectolytic enzyme preparation from Aspergillus niger (pectinase AN) contained laccase activity that decreased rutin content and antioxidant activity of asparagus juice. This research investigated the effects of pH, temperature, and concentration of pectinase AN on pectinase AN’s laccase activity to decrease rutin content and antioxidant activity of asparagus juice. Asparagus juice was incubated with pectinase AN at different pHs (3.2, 4.5 and 5.8), temperatures (25, 37, and 50 °C) and enzyme concentrations (0.1%, 0.5% and 1%). Rutin content and antioxidant activity of samples was determined by HPLC and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) free radical method, respectively. The rate of loss of rutin and antioxidant activity of asparagus juice was smaller at pH 3.2 than at pH 4.5 and pH 5.8, smaller for 0.1% pectinase AN than 0.5% and 1% pectinase AN. The rate of loss of rutin of asparagus juice was greater at 25 °C than at the other two temperatures. Pectinase AN can decrease rutin content and antioxidant activity of asparagus juice at the selected conditions. But rutin content and antioxidant activity of asparagus juice produced using pectinase AN could be less decreased at pH 3.2 and 0.1% of enzyme with less than 2 h of incubation time. This information was helpful for juice industry to produce juices with high antioxidant activity using pectinase AN.     

Accelerated texture softening of some root vegetables by Ohmic heating

Effects of different thermal processing methods (Ohmic heating, high and low power, microwave and conventional heating) on textural properties of cylindrical pieces of root vegetables of carrot, red beet and golden carrot were investigated and compared with conventional and microwave processes. The samples were subjected to different processing methods and textural parameters of the processed samples were analyzed using texture profile analysis (TPA) at different processing times. Texture parameters-processing time data were fitted into a previously suggested equation and texture softening rate (K) and residual constant (A) values were calculated. From the K and A values it can be concluded that not only Ohmic heating resulted in greater softening rates but also the final hardness of the samples treated by Ohmic heating was significantly lower than those of other samples treated by either conventional or microwave methods. Negative correlations were found between texture hardness and weight loss of all samples undergone different processing methods.     

Impact of ethanol treatment on physiological and microbiological properties of fresh white asparagus (Asparagus officinalis L.) spears

Fresh and minimally processed white asparagus (Asparagus officinalis L.) spears are very susceptible to microbial spoilage, often accompanied by changes in physiological and textural quality. To prevent economic losses and to guarantee product quality and safety, postharvest handling and processing need to be improved. New environmentally friendly and safe sanitation techniques should be introduced. This study investigates the efficacy of short-term washing in 0.5 L L⁻¹ ethanol solution at 10 °C as disinfectant of asparagus spears. The prevention of microbial spoilage and treatment effects on physiological properties and value adding quality parameters such as respiration, TSS, vitamin C and water content, and texture were evaluated in fresh white asparagus spears in four harvest seasons. Short-term dipping immediately reduced total bacterial counts and mould loads, and retarded their growth during storage. Retardation apparently did not increase with treatment duration. Short-term (30 s) ethanol washing but not longer treatments result in lower tissue water content and less stiff spears; it also reduced respiration and consumption of sugars. It seems to stabilize the vitamin C contents. Hence, short-term washing with ethanol is a promising approach to improve quality maintenance and safety of fresh asparagus spears and can be easily used in processing lines.     

Microbiological Validation of Microwave-Circulated Water Combination Heating Technology by Inoculated Pack Studies

A 915‐MHz Microwave‐Circulated Water Combination (MCWC) heating technology was validated for a macaroni and cheese product using inoculated pack studies. Before the tests, heat resistances of a Clostridium sporogenes (PA 3679) spore crop were determined in neutral phosphate buffer and macaroni and cheese product. Trays of macaroni and cheese products were subjected to 3 processing levels: target process (F₀= 2.4), under target process (F₀= 1.2), and over target process (F₀= 4.8). The inoculated packs were evaluated by count‐reduction method and end‐point method. The microbial results showed that microbial destruction resulting from MCWC heating technology matched the calculated degree of sterilization (F₀ value). This study suggests that the MCWC heating technology has potential in sterilizing packaged foods.     

Colour and rheological properties of non-conventional grapefruit jams: Instrumental and sensory measurement

Alternative methods with which to obtain grapefruit jams have been applied. These include the use of osmotic dehydration (OD) and/or microwave energy (MW), as an alternative to conventional heating, and the incorporation of bamboo fibre together with pectin in order to increase the jam's consistency. Colour, consistency and rheological behaviour were measured and sensory evaluation was carried out to compare product quality. When compared to the fresh fruit, the greatest colour changes took place in those jams processed by MW and conventional heating, both of them showing lower L*, a*, b* and chrome values than the rest of the samples obtained by applying osmotic dehydration. By adding bamboo fibre, the colour of OD samples approaches that of fresh fruit. The higher yield stress, greater consistency and more viscoelastic behaviour was displayed by jams obtained by combining OD and MW processes. In the sensory analysis, the judges awarded this sample a better score. The sensory attribute product coverage in mouth was closely related to viscosity at a shear rate of 120 s⁻¹ and consistency.     

Towards a freshness test for asparagus: spear tip asparagine content is strongly related to post-harvest accumulated heat-units

The shelf-life of asparagus (Asparagus officinalis L.) is strongly related to the post-harvest accumulated heat-units; the greater the number of accumulated heat-units (degree-h >0°C) experienced by the spears the lower the residual shelf-life. The potential of using asparagine and/or amino acid content as markers of freshness for asparagus spears was assessed by determining the relationship between the concentrations of these metabolites in the spear tips of two cultivars (‘Limbras 10’ and ‘Jersey Giant’) and the post-harvest age of the spears in terms of accumulated heat-units. There was a strong quadratic relationship between spear tip asparagine content and degree-h (R² = 0.878) that was independent of cultivar (P = 0.16). Free amino acid content was also correlated quadratically with degree-h (R² = 0.788 and 0.813 for ‘Limbras 10’ and ‘Jersey Giant’, respectively) but this was cultivar dependent (P = 0.002). Spear tip asparagine concentration has potential as a marker of freshness for asparagus but requires the development of an asparagine assay suitable for use in packhouses or by exporters.     

Enzymatically hydrolysed asparagus (Asparagus officinalis L.) hard-stem exhibits the ability to inhibit angiotensin-converting enzyme (ACE)

Asparagus (Asparagus officinalis L.) hard-stem, woody bottom of the asparagus stalk, is a rich source of bioactive compounds and is discarded as an eco-friendly agricultural waste. Therefore, we intended to explore the antioxidant, amino acid composition, and antihypertensive potentials of enzymatically hydrolysed asparagus hard-stem. The treated samples exhibited higher total free amino acids (11437 mg 100 g⁻¹), total phenolics (1749 mg 100 g⁻¹), and ability to inhibit (78.38%) angiotensin-converting enzyme (ACE) compared to control (ACE inhibition of 46.88%). Hydrophobic amino acids (39%) and gallic acid (48%) were the highly eluted bioactive compounds. The ability to inhibit ACE had been positively correlated with hydrophobic amino acids (r = 0.959–0.987) and gallic acid (r = 0.966), indicating the role of amino acids and phenolics in controlling ACE reactions. Thus, asparagus hard-stem can be a potential source to develop natural health supplements for the management of hypertension and related health risks.     

Antioxidant activity and DNA protection against oxidative damage of bambara groundnut seeds (Vigna subterranea (L.) Verdc.) as affected by processing methods

This research investigated the effects of processing by dry heating, boiling, and steaming on the antioxidant activity and DNA protection against oxidative damage of bambara groundnut seeds (Vigna subterranea (L.) Verdc.). Comparing raw and processed samples of bambara groundnut seeds, dry heating caused a significant (P < 0.05) reduction of ferric-reducing antioxidant power (FRAP), metal chelating activity, DPPH^? and ABTS^?+ radical scavenging activity. The boiling process did not cause a significant difference in FRAP and metal chelating activity and caused smaller losses in DPPH^? and ABTS^?+ radical scavenging activity than the dry heating and steaming processes. The steaming process caused a significant (P < 0.05) reduction of FRAP, DPPH^? and ABTS^?+ radical scavenging activity. For DNA protection against oxidative damage, boiled and steamed bambara groundnut seed samples were more effective with a lower minimum concentration (50 µg/mL) than raw and dry heated samples. These results indicated that the boiling process caused smaller losses antioxidant activity than dry heating and steaming. Therefore, boiling was recommended as processing method for bambara groundnut seeds to preserve antioxidant components and antioxidant activity.     

Physical, chemical and microbiological changes in stored green asparagus spears as affected by coating of silver nanoparticles-PVP

Silver nanoparticles have recently gained increasing interests due to their antimicrobial activities in food processing applications. The aim of this study was to evaluate the effect of silver nanoparticles-PVP coating on weight loss, ascorbic acid, total chlorophyll, crude fiber, color, firmness and microbial qualities of asparagus spears stored at 2 and 10 °C. Asparagus samples were first sanitized with 100 mg l⁻¹ sodium hypochloride solution for 15 min. They were then immersed in coating solution containing silver nanoparticles for 3 min at room temperature. During 25-day storage at 2 or 10 °C, the coated asparagus demonstrated lower weight loss, greener color and tender texture compared with the control samples. The growth of microorganism was significantly hindered by the coating. Based on comprehensive comparison and evaluation, asparagus spears coated by silver nanoparticles could be kept in good quality for 25 days at 2 °C and for 20 days at 10 °C.     

Effect of enzymatic macerate treatment on rutin content, antioxidant activity, yield, and physical properties of asparagus juice

ABSTRACT:  Asparagus is a vegetable with high antioxidant activity. In this research, asparagus juice was produced from fresh asparagus macerate treated with a carbohydrases mixture (Viscozyme) at 37 °C for up to 8 h. Rutin content, antioxidant activity, yield, soluble solid content, and color of the produced asparagus juice were determined. The results showed that Viscozyme significantly increased the yield of asparagus juice, especially in the 1st hour, which was higher than control (without Viscozyme treatment), but the juice had significantly less rutin content than control and had higher antioxidant activity than control only in the 1st 2 h. Juice with Viscozyme treatment had significantly higher soluble solid content than control. The greenness of asparagus juice deteriorates quickly for both the Viscozyme group and control. Viscozyme had advantage in producing juice with high yield, antioxidant activity, and soluble solid content in shorter time (2 h) of treatment compared to control.     

Antioxidant capacity,total phenolics,glucosinolates and colour parameters of rapeseed cultivars

The antioxidant capacity of twenty nine rapeseed varieties was determined by using ferric reducing antioxidant power (FRAP) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) methods. Mean FRAP (3190–6326 μmol Trolox/100 g) and DPPH (3194–6346 μmol Trolox/100 g) values for methanolic extracts of rapeseed cultivars did not differ significantly. Moreover, the total content of phenolics (756–1324 mg sinapic acid/100 g), glucosinolates (4.2–87.5 μmol/g, respectively), erucic acid (0.0–56.1%) and colour parameters of the studied rapeseed cultivars were analysed. Antioxidant capacity determined by FRAP and DPPH methods correlated significantly with total phenolic content (TPC) in rapeseed cultivars (r = 0.9332, 0.9339, p < 0.001). Also, significant, inverse correlations were found between antioxidant capacity, total phenolics and luminosity (L^∗) or red colour intensity (a^∗) of rapeseed cultivars. Principal component analysis (PCA) allowed the rapeseed varieties to be differentiated based on their antioxidant capacities, total amounts of phenolics, glucosinolates, erucic acid and colour parameters.     

Saponin Profile of Wild Asparagus Species

The aim of this work was to study the saponin profiles from spears of different wild asparagus species in the context of its genetic diversity aside from geographical seed origin. They included Asparagus pseudoscaber Grecescu, Asparagus maritimus (L.) Mill., Asparagus brachiphyllus Turcz., Asparagus prostrates Dumort., and Asparagus officinalis L. The saponin analysis by LC‐MS has shown that saponin profile from wild asparagus is similar to that previously described for triguero asparagus from Huétor‐Tájar landrace (triguero HT), which had not ever been reported in the edible part of asparagus. All the samples, except A. officinalis, were characterized for having saponins distinct to protodioscin and the total saponin contents were 10‐fold higher than those described for commercial hybrids of green asparagus. In particular, A. maritimus from different origins were rich in saponins previously found in triguero HT. These findings supported previous suggestion, based on genetic analysis, about A. maritimus being the origin of triguero HT. Multivariate statistics including principal component analysis and hierarchical clustering analysis were used to define both similarities and differences among samples. The results showed that the greatest variance of the tested wild asparagus could be attributed to differences in the concentration of particular saponins and this knowledge could be a tool for identifying similar species.     

Development of a rapid HPLC-UV method for simultaneous quantification of protodioscin and rutin in white and green asparagus spears

Abstract: Asparagus (Asparagus officinalis L.) spears are rich in bioactive compounds such as protodioscin, a saponin, and rutin, a flavonoid. Protodioscin and rutin are routinely quantified separately, and an approach permitting simultaneous measurement would significantly improve speed of analysis. We have optimized an extraction procedure and modified a method of high-performance liquid chromatography by coupling to an ultraviolet detector to simultaneously analyze protodioscin and rutin in asparagus extracts. An acidic ethanol solvent was more efficient than methanol, acetonitrile, or water in coextraction of protodioscin and rutin. Protodioscin and rutin were detected at 210 nm, with retention times of 12.6 min and 7.9 min, respectively. The method was validated by high linear correlations between 3.13 and 1000.0 μg/mL for protodioscin (r²= 0.9999), and between 0.3 and 1087.5 μg/mL for rutin (r²= 0.9997). The limit(s) of detection and quantification for protodioscin were 1.6 μg/mL and 3.13 μg/mL, respectively, and for rutin 0.2 μg/mL and 0.3 μg/mL, respectively. White asparagus spears and the crown of the plants were revealed to be rich sources of protodioscin and contained 2.59 to 10.4 mg/g dry weight. Green asparagus spears, particularly the upper portion, were rich in rutin and contained between 1.51 and 7.29 mg/g dry weight.     

Use of HPLC–DAD–ESI/MS to profile phenolic compounds in edible wild greens from Portugal

In some Mediterranean areas traditional wild greens are responsible for a significant percentage of total dietary antioxidant intakes. Asparagus acutifolius L. (wild asparagus), Bryonia dioica Jacq. (white bryony) and Tamus communis L. (black bryony) are important examples of those edible wild greens widely consumed. This study aimed to determine the phenolic profile and composition of edible vernal early shoots of those species. Wild asparagus and black bryony revealed glycosides of flavonols as the main phenolic compounds, while white bryony contained C-glycosylated flavones. Black bryony was the wild green that possessed the highest content of phenolic compounds (2200 mg/kg). Amongst the 11 flavonols found in this sample, kaempferol glycosides were the main compounds (1760 mg/kg). In the sample of wild asparagus, quercetin 3-O-rutinoside was the main flavonol found (263 mg/kg). Five flavones and one flavonol were found in the white bryony sample, apigenin 6-C-glucoside-7-O-glucoside being the major compound (1550 mg/kg).     

Quality and consumer acceptance of radio frequency and traditional heat pasteurised kiwi puree during storage

To explore the feasibility of using radio frequency (RF) heating as a method to process kiwi puree, this study compared the effects of RF heating with traditional heat pasteurisation (TP) on various properties of kiwi puree. RF treatment completely inactivate of microbes in kiwi puree, with total aerobic bacteria counts (TAC) decreased by 4.81 log CFU mL^?1 and yeast and mould counts (YMC) decreased by 2.62 log CFU mL^?1, which are similar to TP treatment. During the 7 weeks’ storage, RF‐treated puree showed retarded growth of microbes. The pH, titratable acidity and °Brix values of RF‐treated samples were significantly different from those of the control. The vitamin C, total phenolic compounds and antioxidant capacity of RF‐treated samples were significantly higher than those of TP‐treated samples during storage. RF‐treated sample retained better colour than TP‐treated sample throughout storage. The customer satisfaction analysis indicated that consumers prefer RF‐treated kiwi puree than TP‐treated samples. These findings suggest that RF heating has potential applications in processing of kiwi puree or similar products.     

Relationship and correlation between antioxidant content and capacity,processing method and fruit colour of cactus pear fruit

Cactus pear fruit is a valuable source of antioxidants and could be an important functional ingredient in foods. Cultivars differ in fruit colour, which may indicate the presence of specific antioxidants. There is increased interest for cactus pear-derived products due to their potential nutraceutical effects, and determining antioxidant potential in processed foods is an important measure to ascertain the quality of a processed product. The aim of the study was to determine the relationship of fruit processing method and colour with antioxidant content and activity in fresh and processed cactus pear fruit. Antioxidant components (ascorbic acid, phenolic compounds, carotenes and betalains) and antioxidant activity (radical scavenging activity towards 2,2′-diphenyl-1-picrylhydrazyl and iron chelating capacity) were determined in fresh and processed (juiced, dried, preserved and chutney) fruits from four different coloured cultivars (purple, green, orange and pink). The highest antioxidant content and potential was found in purple (O. robusta cv Robusta) fruit products, attributed to the highest levels of betalains (1140.4 mg kg^?1). Orange fruit (O. ficus-indica) products had the second highest levels, attributed to ascorbic acid and phenolics. Betalains were highly retained in all processed products, while ascorbic acid was mostly retained in the processed products that involved minimal heat treatment. Carotene and phenolic compounds became more available for extraction during processing and showed higher levels after processing. Principal component analysis makes it possible to identify fruit colours of fresh and processed products, which were mostly associated with a specific antioxidant. In the PCA biplot, PC1 (47.93%) and PC2 (21.93%) explained 69.15% of the total variation: a processing method rather than colour-correlated products in terms of antioxidant content and potential. PCA indicated that fresh purple fruit was correlated with chelating activity and betalains, while orange fruit was clustered with phenolics, ascorbic acid, carotene and DPPH. For the processed fruit products, most were clustered together with chelating activity, DPPH and the antioxidants. Orange and pink dried products had high ascorbic acid, phenolics, carotene and DPPH values, while dried and fresh purple fruit had high betalain content and chelating activity.     

Quality and shelf-life of washed fresh-cut asparagus in modified atmosphere packaging

Fresh-cut asparagus is one of the most popular fresh vegetables for healthy consumption. However, the level of microbial load in the raw vegetable can cause food poisoning and shorten its shelf-life of asparagus. The objectives of this work were to determine the effect of chlorinated and ozonated water in the washing process to reduce the microbial load on fresh green asparagus and the effect of modified atmosphere packaging (MAP) on asparagus quality. Washing at 10 °C for 15 min with chlorinated water (100 mg/L free Cl₂) reduced aerobic plate count which had higher efficiency on microbial reduction than the use of ozonated water (0.1 mg/L O₃). No significant differences on the amount of Escherichia coli contamination among washing methods were found. Asparagus in modified atmosphere packaging retarded the deterioration process. Changes in hue angle followed a first-order kinetic reaction. Temperature dependence of the kinetic rate constant during storage time of asparagus obeyed the Arrhenius relationship with an activation energy (E_a) 29.33 ± 4.60 kJ/mol. The shelf-life prediction equation was related well with real practice. The combination of appropriate washing process and MAP increased the food safety, maintained the quality and prolonged the shelf-life of asparagus.     

Effect of the extraction method on phytochemical composition and antioxidant activity of high dietary fibre powders obtained from asparagus by-products

Asparagus (Asparagus officinalis L.) spears are highly appreciated for their composition of bioactive compounds. The method by which their by-products are treated affects the phytochemical composition and antioxidant activity of the fibre-rich powders. Factors such as the treatment intensity, the solvent used, and the drying system were studied. Among the asparagus phytochemicals, hydroxycinnamic acids (HCA), saponins, flavonoids, sterols, and fructans were quantified. HCA varied from 2.31 and 4.91 mg/g of fibre, the content being affected by the drying system and, in some cases, the solvent. Fibres from intense treatments had significantly higher amounts of saponin than samples isolated by gentle treatments. Saponin content ranged from 2.14 to 3.64 mg/g of fibre. Flavonoids were the most affected by processing conditions, being present (0.6–1.8 mg/g of fibre) only in three of the samples analysed. Continuous stirring during processing could be the main reason for this result. Sterols and fructans were present in minor amounts, 0.63–1.03 mg/g of fibre and 0.2–1.4 mg/g of fibre, respectively. Soluble and total antioxidant activities were also measured. Fibres with the highest activities corresponded to those with the highest levels of flavonoids and HCA.