The impact of high pressure on glucosinolate profile and myrosinase activity in seedlings from Brussels sprouts

The potential of high pressure (HP) to control bioactive components using seedlings of Brussels sprouts as a simple non-chopped vegetable system was examined. Enzyme activity in situ compared to purified enzyme and residual enzyme substrate in situ are used as three complementary measures for the HP effect. Purified myrosinase and seedlings of Brussels sprouts were submitted to HP 200–800 MPa at 5 °C for 3 min. The myrosinase activity decreased for both myrosinase systems upon increasing pressure to 800 MPa. Applying first-order kinetic to determine activation volumes revealed a linear relationship from 400 to 600 (ΔV^# = − 19.04 mL/mol) and 450–600 MPa (ΔV^# = − 37.79 mL/mol) for seedlings and purified myrosinase, respectively, indicating a protective effect of the plant matrix against enzyme inactivation. Purified myrosinase was activated at 200 MPa but at 800 MPa the glucosinolate degradation due to pressure induced disruption of the plant matrix seems to be partly counter-acted by myrosinase inactivation.Industrial relevanceHigh Pressure (HP) processing is an effective non-thermal preservation treatment for liquid and solid food. Moreover, over the last years, the potential of this technology to improve health and safety attributes of foods has been demonstrated. In particular, the ability of HP to preserve bioactive compounds has been established. There are only few studies evaluating the impact of HP on the complex bioactive glucosinolates-myrosinase. Therefore, this study opens the doors through the application of HP to preserve the bioactive glucosinolates in cruciferous vegetables by creating new processing solutions through controlled enzyme inactivation. Thus, HP could be an effective tool to achieve more effective solutions to obtain the new generation of convenient food and meet the need for new bioactive food products.     

Effects of abscisic acid on glucosinolate content,isothiocyanate formation and myrosinase activity in cabbage sprouts

Effects of abscisic acid (ABA) on glucosinolate content, isothiocyanate formation and myrosinase activity in cabbage sprouts were investigated. Subsequently, their distributions in different organs were evaluated. ABA (50 μmol L^?1) significantly increased glucosinolate content, isothiocyanate formation and myrosinase activity by 72.65%, 268.15% and 67.69%, respectively, in 5‐day‐old sprouts. Application of ABA alleviated the decrease rate of glucosinolate content and increased the myrosinase activity during germination. Besides, isothiocyanate formation rapidly increased after germinating for 3 days. The glucosinolate content and isothiocyanate formation reduced by 46.51% and 38.01%, respectively, in fluridon (Flu)‐treated sprouts. Cotyledon of ABA‐treated sprouts had the highest glucosinolate content and isothiocyanate formation, indicating that ABA was necessary to enhance the isothiocyanate formation in cabbage sprouts by increasing glucosinolate content and myrosinase activity.     

Effect of high pressure processing and storage on the free amino acids in seedlings of Brussels sprouts

The potential of high pressure (HP) to affect the content of free amino acids (FAA) using seedlings of Brussels sprouts as a simple non-chopped vegetable system was examined. Firstly, the effect on FAA composition during growth was assessed and it was found that the composition of total free amino acids (TFAA) and individual FAA changed dramatically during growth of the seeds to the seedling at 7 days with the highest content of TFAA. Secondly, 7-day-old seedlings were HP-treated at various pressure levels (200–800 MPa for 3 min at 5 °C). As expected the HP-treatment did not affect the amino acids as no changes in TFFA were found immediately after pressurisation. In this line, HP-treatment up to 800 MPa had minor, but significant, effect on the FAA concentrations of 10 FAA (Ala, Asp, Glu, Gly, Leu, Phe, Pro, Ser, Trp and Tyr) and no significant changes were found for 7 of the FAA (Asn, Gln, His, Ile, Lys, Thr, and Val) concluding that the short pressure time (3 min) was insufficient to activate indigenous proteolytic enzymes. Furthermore, changes in the FAA content and composition of HP-treated seedlings during storage (0, 1, 2, and 4 days at 4 ± 2 °C) were evaluated in order to assess changes in the proteolytic enzyme activity. It was found that the changes in FAA differed according to the specific amino acids as well as the HP processing conditions and the subsequent storage time. These results suggest that HP treatment affects proteolysis and/or certain amino acids metabolism pathways in Brussels sprouts seedlings after HP treatment and during subsequent storage.     

Myrosinase activity and total glucosinolate content of cruciferous vegetables,and some properties of cabbage myrosinase in Taiwan

The myrosinase activity and total glucosinolates of 10 different cruciferous vegetables and some properties of cabbage (Brassica oleracea L var capitata L) myrosinase were investigated. Radish, cabbage and broccoli showed higher myrosinase activity than other samples. No correlation (P > 0–05) was found between myrosinase activity and total glucosinolates of cruciferous vegetables tested. Myrosinase activity for white cabbage was higher than red cabbage. An optimal pH of myrosinase activity was observed at pH 8–0 for both white and red cabbages. The myrosinase extracted from cabbage was more stable in neutral or alkaline pH. The optimal temperature of myrosinase activity for both cabbages was about 60°C, but the myrosinase activity was destroyed after heating at 70°C for 30 min. The myrosinase activities of both white and red cabbages were activated by 10 mM and 5 mM ascorbic acid, respectively.     

Effect of salt stress on phenolic compounds,glucosinolates, myrosinase and antioxidant activity in radish sprouts

The germination, growth, total phenolics, glucosinolate, myrosinase and antioxidant activity of radish sprouts germinated under 0 (control), 10, 50 and 100 mM of NaCl were investigated. The glucoraphasatin (4-methylthio-3-butenyl-glucosinolate), total glucosinolate and total phenolic contents of 5- and 7-day-old sprouts treated with 10 and 50 mM of NaCl were significantly decreased. However, the antioxidant activity of sprouts treated with 10 and 50 mM of NaCl was not affected. The glucoraphasatin and total glucosinolate contents of 5- and 7-day-old sprouts, total phenolic contents of 3- and 5-day-old sprouts were significantly increased and myrosinase activities of 3- and 5-day-old sprouts were inhibited, although the germination was dramatically inhibited by 100 mM of NaCl treatment. These results indicated that salt stress (100 mM of NaCl treatment) could improve the nutritional value of radish sprouts, and germination of sprouts under adequate salt stress could be one useful way to enhance health-promoting compounds of plant food.     

The contribution of high pressure carbon dioxide in the inactivation kinetics and structural alteration of myrosinase

High pressure carbon dioxide (HPCD) has been verified to be an efficient way of inactivating enzyme activity. This work investigates the influence of temperature (T), pressure (P), exposure times (t) on the activity of commercial myrosinase (MYR) submitted to HPCD. Results showed that only 1.00% of MYR activity retained at 22 MPa and 65 °C for 5 min. Moreover, the first‐order reaction kinetic data of MYR inactivation as influenced by pressure of HPCD were analysed. With the pressure rising from 8 to 22 MPa at 55 °C, the inactivation rate constant (k) increased from 0.015 to 0.024 min^?1, while the decimal reduction time (D) decreased from 157.2 to 96.1 min. Additionally, a series of exploratory experiments were conducted to investigate the contribution of the HPCD parameters (T, P and CO₂ dissolution), with analysing circular dichroism spectroscopy and tryptophan fluorescence spectra, illustrate that CO₂ dissolution plays a dominant role in MYR inactivation and structural alteration.     

Thermal and high hydrostatic pressure inactivation of myrosinase from green cabbage: A kinetic study

Myrosinase, a family of enzymes which coexist with glucosinolates in all Brassica vegetables, catalyses the hydrolysis of glucosinolates to yield compounds that can have beneficial effects on human health. In this study, the thermal and pressure inactivation of myrosinase from green cabbage was kinetically investigated. Thermal inactivation started at 35 °C and inactivation kinetics was studied in the temperature range 35-55 °C. Thermal inactivation of green cabbage myrosinase followed the well known consecutive step model. Pressure inactivation started at 300 MPa, even at 10 °C, and the consecutive step model effectively described pressure inactivation in the range 300-450 MPa at 10 °C. The combined effects of applying various pressures and temperatures on myrosinase inactivation kinetics were studied in the ranges 35-50 °C and, 100-400 MPa. The inactivation followed first-order kinetics at all of the applied combinations. This study demonstrates that myrosinase from green cabbage is highly susceptible to both thermal and high pressure processing. Furthermore, it is also noted that myrosinase stability during processing appears to vary widely between different Brassica species.     

Inositol phosphate content and trypsin inhibitor activity in ready-to-eat cruciferous sprouts

Four cruciferous seeds (small radish, radish, white mustard and rapeseed) were germinated in order to study the fate of inositol hexaphosphate (IP-6, phytic acid) and activity of trypsin inhibitor (TIA). Reduction in the content of phytic acid depended on the time of germination. After four days of germination, when sprouts were ready-to-eat, the amount of this compound was about 50% lower in three out of the four seeds evaluated. Next, a sharp reduction in phytic acid occurred during thermal treatments (pasteurization and sterilization) of germinated rapeseed and radish sprouts. In thermal processes, a decrease in inositol hexaphosphate content was accompanied by the appearance of lower forms of inositol phosphates: IP-5, IP-4 and IP-3.The analysis of TIA, in rapeseed and radish seeds, in four-day sprouts and in these sprouts after thermal treatment, showed that only thermal processes caused complete disappearance this activity.     

The effect of light and temperature on glucosinolate concentration in the leaves and roots of cabbage seedlings

In previous studies it was shown that the concentration of total and individual glucosinolates in brassicaceous plants can vary significantly over a 24-h period grown either in the field or under controlled conditions. The present study shows total and individual glucosinolate variation during a single day. Seedlings of cabbage grown under controlled conditions and at 14 and 15 days after emergence were moved to 20°C (Exp A) and 30°C (Exp B), with a constant photosynthetic photon flux density of 480 μmol m⁻² s⁻¹ and 75% relative humidity, over a 2-day period, during which time aerial parts and roots were sampled at regular intervals. Whilst the glucosinolate patterns of the aerial part of the plant and of the roots remained the same, the levels of major glucosinolates in the aerial part, averaged over all sampling times and 2 days, were 233 ± 60 μmol 100 g⁻¹ DW for 3-methylsulphinylpropyl and 72 ± 22 for 2-propenyl; in the roots, 2-phenylethyl and 1-methoxyindol-3-ylmethyl showed the highest average concentrations, with 678 ± 355 μmol 100 g⁻¹ DW and 411 ± 122, respectively. Total and individual glucosinolate levels showed very high significant differences between the two plant parts. Despite the constant temperature, light and relative humidity, glucosinolates varied within a 24-h period, showing ultradian rhythms that are common to several metabolic processes in plants. The results confirm previous observations that at a temperature of 20°C, close to the optimum for growth and development, the diurnal variation in glucosinolate concentration, was smaller than at 30°C. © 1998 Society of Chemical Industry     

国产玛咖芥子油苷的组分分析和含量测定

目的:对国内不同颜色、不同地区的玛咖,及玛咖不同部位的芥子油苷的主要组分和含量进行鉴定和分析。方法:将玛咖粉末用70%甲醇提取,过DEAE-SephadexA-25阴离子交换柱后,加硫酸酯酶后于37℃的恒温箱酶解,洗脱液用LC-MS法分析其成分和含量。结果:各种不同玛咖的主要芥子油苷组分相同,均检测到苄基芥子油苷和间-甲氧基苄基芥子油苷这2种芳香族芥子油苷,其中前者占总含量约75%。芥子油苷在不同颜色玛咖中含量差异较小;在玛咖叶片、块根、须根3个不同部位含量差别很大,须根中含量高于主根,主根中高于叶片。同时,国内不同地区玛咖中芥子油苷含量也有较大差别。结论:使用LC-MS法可对国产玛咖中所含的芥子油苷组分及含量进行准确分析。     

The glucosinolates sinigrin and progoitrin are important determinants for taste preference and bitterness of Brussels sprouts

The glucosinolates, sinigrin and progoitrin, are related to the bitterness observed in Brussels sprouts. The role of these glucosinolates in taste preference for Brussels sprouts (Brassica oleracea var gemmifera) was studied with two different consumer taste panels and an analytical panel. Four different taste trials were conducted between 1989 and 1995 to study the role of sinigrin and progoitrin on taste preference and bitterness of sprouts. Sinigrin and progoitrin correlated negatively with taste preference of sprouts when their combined content was higher than 2·2 g kg⁻¹. Under these conditions the overall preference for different Brussels sprouts cultivars, in two different trial designs, was accounted for, respectively, 64 (Novartis Seeds BV) and 86% (TNO) by the contents of the glucosinolates sinigrin and progoitrin. In two additional trials, in which the combined content of sinigrin and progoitrin of all cultivars was below 2·2 g kg⁻¹, no relationship between taste preference and the content of both glucosinolates was observed. In the latter trials the content of sinigrin and progoitrin was found to be correlated with bitterness (r²_multiple = 0·67 and 0·93, respectively) as assessed by an analytical panel. The results of the taste trials show that both bitterness and taste preference for sprouts are correlated with the content of sinigrin and progoitrin. Taste preference for sprouts is only correlated with sinigrin and progoitrin when their combined content exceeds 2·2 g kg⁻¹, while bitterness is correlated with both glucosinolates for the whole studied content range. © 1998 Society of Chemical Industry.     

加水量对小麦拉丝蛋白品质的影响

为了更好地调控小麦拉丝蛋白的品质,解决其复水率低、弹性小、组织化程度低等问题,以谷朊粉为原料,利用双螺杆挤压机,研究了挤压过程中加水量对小麦拉丝蛋白品质特性(组织化度、硬度、弹性、咀嚼度、内聚性、复水率、堆积密度)及微观结构的影响。结果表明,在一定温度条件下,加水量低于30%时,小麦拉丝蛋白的膨化度、复水率低,堆积密度大,加水量高于50%时,小麦拉丝蛋白的组织化度变小,弹性、硬度、咀嚼性等指标降低。电镜结果显示,随着加水量的增大小麦拉丝蛋白表面出现明显的纤维结构,当加水量超过50%时,拉丝蛋白表面出现明显气孔。加水量在40%时,拉丝蛋白的硬度、弹性等参数最佳,堆积密度较小,复水率最高,且纤维结构最明显,组织化度也得到明显改善。     

Effect of thermal processing on phenolics, antioxidant activity and health-relevant functionality of select grain sprouts and seedlings

The effect of thermal processing via autoclaving on modifications of total phenolics, antioxidant activity and functionality of wheat, buckwheat, corn and oats sprouts and seedlings were investigated. Functionality for type 2 diabetes related α-amylase, α-glucosidase inhibition and levo-dihydroxy phenylalanine (l-DOPA) content, hypertension related angiotensin converting enzyme 1 (ACE) inhibition and ulcer related Helicobacter pylori inhibition were evaluated using in vitro assays. Thermal processing in general resulted in tissue browning leading to higher total phenolic content and free radical scavenging-linked antioxidant activity. It increased α-amylase inhibitory activity in buckwheat and oats but decreased in wheat and corn sprouts and seedlings. It increased α-glucosidase inhibitory activity in wheat, buckwheat and oats but decreased in corn sprouts. It reduced the cognitive function/diabetes related l-DOPA content in all grains sprouts and seedlings tested. It increased ACE inhibitory activity in buckwheat and oats, but decreased in wheat and corn sprouts. It also improved the ulcer related H. pylori inhibitory activity in all grain sprouts and seedlings studied. These changes in functionality are suggested to be due to modifications in the total phenolic content and profile by phenolic oxidation or polymerization caused by thermal processing. Therefore, diet designs for chronic disease management will have to consider thermal processing-linked modification of bioactive ingredient profiles.

Industrial relevance

Thermal processing altered the total phenolic content and antioxidant activity in winter wheat, buckwheat, corn and oats sprouts and seedlings. It modified the α-amylase inhibitory activity, α-glucosidase inhibitory activity, l-DOPA content, ACE inhibitory activity and H. pylori inhibitory activity of samples. Therefore, the food processing industry and diet design for chronic disease management will have to consider thermal processing-linked modification of bioactive ingredient profiles for more effective health benefits.     

Effects of polyvinylchloride films and edible starch coatings on quality aspects of refrigerated Brussels sprouts

To extend shelf life, the effects of polyvinylchloride film (PVC) and edible coatings on quality aspects of refrigerated Brussels sprouts were studied. Starch-based coatings were formulated using glycerol (G), sorbitol (S) or glycerol plus sunflower oil (O). Sprouts so treated as well as uncoated ones were placed on expanded polystyrene trays. Combinations of PVC and coatings (treatments named G-PVC, S-PVC and O-PVC) were also tested. Uncovered trays were maintained as controls. All packages were stored at 0 °C for 42 days and samples were removed every 14 days to determine commercial acceptability, weight loss, surface colour (of sprouts’ heads and bases) and texture. Sprouts in all treatments maintained optimum quality conditions over the first 14 days. At the end of storage, browning of cut zones and losses in weight and firmness were minimised in PVC-packaged sprouts, particularly in G-PVC. Therefore, PVC and G-PVC treatments were selected to evaluate some nutritional quality components. Ascorbic acid and total flavonoid contents remained almost constant while radical scavenging activity increased after 42 days of storage. Thus, PVC and G-PVC treatments showed the best performance for long-term refrigerated storage of Brussels sprouts.     

干燥方式对苦荞麦芽色泽、多酚及抗氧化活性的影响

研究了真空冷冻干燥、热风干燥、微波干燥、自然阴干和晒干对苦荞麦芽色泽及甲醇提取物中多酚含量、组分和抗氧化活性的影响。结果表明:不同干燥方式对苦荞麦芽色泽、多酚含量和组分及抗氧化活性有显著影响。真空冷冻干燥及60℃热风干燥的苦荞麦芽色泽变化最小,自然阴干的荞麦芽色泽最差。苦荞麦芽中含多种多酚化合物,含量最高的是芦丁,其次为槲皮素和绿原酸,干燥方式对这些成分均有显著影响。真空冷冻干燥、60℃热风干燥及自然阴干的样品中总黄酮和多酚显著高于其他干燥方式,且样品具有较强的抗氧化活性,结合干燥时的色泽变化,真空冷冻干燥和60℃热风干燥用于苦荞麦芽干燥可最大程度的保持荞麦芽色泽和活性成分,在实际应用中,可根据情况选择使用。     

Effects of high pressure processing on antioxidant activity, and total carotenoid content and availability, in vegetables

High pressure processing (HPP) is a relatively new food preservation processing technology that enhances food safety and shelf-life without compromising organoleptic qualities. There has been little research on the impact of HPP on the nutritional and health-promoting properties of foods to date and most of it has focused on juices and purees of fruit such as oranges and tomatoes. The objective of this study was to determine the effects of HPP treatment at two pressure levels (400 MPa; 600 MPa) on antioxidant activity, total carotenoid content and carotenoid availability in vitro, of three commonly consumed vegetables. Antioxidant capacity and total carotenoid content differed between vegetables but were unaffected by HPP treatment. In vitro availability of specific carotenoids also varied greatly between vegetables (3–35%). HPP altered availability of carotenoids according to the type of vegetable treated and processing pressure applied, however the magnitude of the responses was minor.

Industrial relevance

This study provides further scientific evidence of the benefits of high pressure processing in retaining the nutritional attributes of fresh foods. Antioxidant activity and levels of carotenoids before and after exposure to high pressures (up to 600 MPa for 2 min) were essentially no different. Also, the data suggest that micronutrients and phytochemicals in certain vegetables may be made more bioavailable by high pressure treatment. From a nutritional perspective, high pressure processing is an attractive food preservation technology and clearly offers opportunities for horticultural and food processing industries to meet the growing demand from consumers for healthier food products.