Effect of thermal and high pressure processes on structural and health-related properties of carrots (Daucus carota)

In the present study, the effect of thermal and equivalent high pressure processes on structural (texture and microstructure) and health-related (total β-carotene concentration, β-carotene isomerisation and β-carotene bio-accessibility) properties of carrots was investigated. Both a mild and strong pasteurisation process and a sterilisation process were considered.     

Impact of boron, calcium and genetic factors on vitamin C, carotenoids, phenolic acids, anthocyanins and antioxidant capacity of carrots (Daucus carota)

Carrots (Daucus carota L.) were used to investigate the effects and interactions of cultivar and mineral supply on the nutritional quality (antioxidant potential, vitamin C, carotenoids and phenolic acids) of the resulting storage roots. The supplement of boron (B) and or calcium (Ca) in the feeding solutions, during plant growth, influenced the accumulation of other minerals, such as P, K, Mg, S and Na, in the storage roots (p < 0.05). When no additional B or Ca was supplied (e.g. −B or −Ca treatment), we observed 33-50% increase in the accumulated levels of α- and β-carotenes, and 45-70% increase of vitamin C. Carrots grown with no supplement of B in the nutrient solutions (e.g. −B treatment and −ve control) had significantly higher (p < 0.001) levels of total phenolic acids compared to the carrots with the supplement of B (e.g. −Ca treatment and +ve control). A strong positive correlation was observed between the total phenolic contents and ORAC values (r = 0.932) in all the cultivars. The results suggest that both cultivar and mineral supply were major determinants of nutritional quality of the carrots. The nutritional value of carrot crops (with an acceptable physical quality) can be enhanced by manipulating mineral nutrient applications.     

Inhibition of polyphenol oxidase and peroxidase activities on fresh-cut apple by simultaneous treatment of ultrasound and ascorbic acid

The effects of ultrasound and ascorbic acid on activity changes of polyphenol oxidase and peroxidase, of fresh-cut apple during storage, were investigated. The combined treatment of ultrasound and ascorbic acid inactivated monophenolase, diphenolase, and peroxidase, whilst the individual treatment of ultrasound or ascorbic acid had inverse and limited inhibitory effect on the enzymes. The main protein bands had a molecular weight of approximately 63 kDa. A diffuse band, lacking the electrophoretic mobility of proteins, was observed after combined treatment. This investigation revealed that simultaneous treatment with ultrasound and ascorbic acid had synergistic inhibitory effects on several enzymes related to enzymatic browning.     

Apple polyphenoloxidase inactivation during heating in the presence of ascorbic acid and chlorogenic acid

It was recently reported that during osmotic dehydration of ascorbic acid (AA)-treated apple cubes, losses in AA and phenolics could partly arise from enzymatic oxidation, provided polyphenoloxidase (PPO) was still active under the processing conditions. To determine the impact of dehydration temperatures on PPO action, as well as chemical and enzymatic oxidation reactions, apple PPO inactivation alone or with AA (1 mM) and/or chlorogenic acid (CG, 3 mM), as well as AA and CG levels evolution, during heating of the model solutions at 45 and 60 °C were investigated. At pH 3.8, PPO was still functional, keeping 61 and 4% residual activity after 2 h of heating at 45 and 60 °C, respectively. The combined treatment of heating and AA was more effective in reducing PPO activity, while incubation at 60 °C with AA and CG minimised the losses of PPO activity. CG remained stable during heating, even in the presence of AA which, in turn, was more affected by heating. Thus, during heating, provided PPO remained active with enough available O₂ in the model systems, CG oxidation and coupled oxidoreduction with AA could readily develop.     

Investigation of bitterness in carrots (Daucus carota L.) based on quantitative chemical and sensory analyses

Bitterness is considered as an undesirable taste of carrots. Quantitative chemical analysis of potential bitter compounds of different carrot genotypes was combined with sensory analysis in order to identify key compounds likely to be responsible for the bitterness of carrots. Eight carrot genotypes (‘Bolero’, ‘Mello Yello’, ‘Nairobi’, ‘Tornado’, ‘Purple Haze’, ‘Line 1’, ‘Line 2’, and ‘Line 3’) representing extremes in sensory-perceived odour, flavour, and taste. Potential bitter compounds like polyacetylenes, isocoumarins and phenolic acids were quantified in the peel and the corresponding peeled carrot, and their contribution to bitterness in raw carrots was analysed by sensory profiling using multivariate data analysis. Falcarindiol and a di-caffeic acid derivative were highly related to bitterness in contrast to falcarinol and other potential bitter compounds. Falcarindiol and the di-caffeic acid derivative were primarily present in the peel whereas falcarinol was almost evenly distributed in the root. Investigation of bitterness revealed that high sugar content to some extent could mask the bitter perception of carrots. As falcarinol is the most bioactive of the carrot polyacetylenes the results of the present study indicate that there is a basis for improving the health effects of raw carrots without affecting sensory quality.     

Effect of high pressure processing on the stability of anthocyanin,ascorbic acid and color of Chinese bayberry juice during storage

The stability of anthocyanin (Cy3Gl) and ascorbic acid (AA) of pressure treated Chinese bayberry (Myrica rubra Sieb. et Zucc.) juice was investigated during storage at temperature of 4 °C and 25 °C. Samples of Chinese bayberry juice (350 mL each, packed with a polyethylene bag) were processed at 400, 500, 600 MPa in room temperature for 10 min. The retention ratio of Cy3Gl and AA content after pressure treatment was more than 98% and 96%, respectively. Both Cy3Gl and AA of pressure treated juice were more stable during storage as compared to those of the untreated control juice. The degradation of Cy3Gl and AA of samples during storage could be described using first order kinetic model. It was observed that there was a significant (p < 0.01) correlation between changes of Cy3Gl and AA content for all tested samples of Chinese bayberry juice during storage.     

Characterization and thermal lability of carotenoids and vitamin C of tamarillo fruit (Solanum betaceum Cav.)

The carotenoids from yellow tamarillo were determined by high-performance liquid chromatography-photodiode array detection/mass spectrometry (HPLC-PDA/MS). Xanthophylls were found as esterified with palmitic and myristic acids. All-trans-β-cryptoxanthin esters and all-trans-β-carotene were the major carotenoids of tamarillo. Changes in carotenoid and vitamin C contents after thermal pasteurization of degassed and not degassed tomato tree nectars were studied. Zeaxanthin esters appeared to be the less thermo-labile carotenoids. Carotenoids degradation was not significantly influenced by dissolved oxygen level. However, thermal treatment induced 5,8-epoxidation and cis-isomerization. Retention of ascorbic acid was total under degassed conditions while losses of dehydroascorbic acid were not affected by the initial level of dissolved oxygen.     

Application of thermal inactivation of enzymes during vitamin C analysis to study the influence of acidification,crushing and blanching on vitamin C stability in Broccoli (Brassica oleracea L var. italica)

The effectiveness of heat inactivation of oxidative enzymes e.g., ascorbic acid oxidase (AAO) to stabilise vitamin C during extraction and analysis was evaluated. The influence of different sequences of performing treatments including acidification (pH 4.3 vs. pH 6.5), crushing, high temperature short time (90 °C/4 min–HTST) and low temperature long time (60 °C/40 min–LTLT)) blanching on vitamin C stability in broccoli florets and stalks was also investigated. Heat inactivation of enzymes prior to matrix disruption resulted in higher vitamin C values mainly in L-ascorbic acid (L-AA) form, while lack of enzyme inactivation resulted in high vitamin C losses resulting from conversion of L-AA to dehydroascorbic acid. Various treatments and their sequence of application influenced vitamin C stability as follows: (i) crushing prior to blanching reduced vitamin C stability and (ii) in the absence of heating, acidification increased vitamin C stability (iii) blanching prior to crushing resulted in higher vitamin C retention, with HTST blanching retaining more vitamin C than LTLT blanching.     

Changes in vitamin C content and antioxidant capacity of raw and germinated cowpea (Vigna sinensis var. carilla) seeds induced by high pressure treatment

The effect of high pressure treatment on the vitamin C content and antioxidant capacity of raw and germinated cowpea seeds (Vigna sinensis var. carilla) at 300, 400 and 500 MPa for 15 min at room temperature has been investigated. A considerable amount of vitamin C was detected in germinated cowpeas, but the vitamin was not detected in raw seeds. An increase on the antioxidant capacity (TEAC) in cowpea sprouts was also observed (58–67%). High pressure treatment (HP) slightly modified vitamin C content and TEAC and, after pressurization at 500 MPa, the decrease was more pronounced, although the germinated seeds submitted to this HP treatment still provided a high amount of vitamin C (15–17 mg/100 g d.m.) and the antioxidant capacity was 26–59% higher than that of the raw cowpeas. The HP process can provide minimally processed fresh-like sprouts of high quality.     

Comparative evaluation of UV-HPLC methods and reducing agents to determine vitamin C in fruits

Vitamin C is one of the most important antioxidant supplied by fruits and vegetables. Therefore a reliable and easy method is needed for its determination. In this work, two UV-HPLC methods for the determination of ascorbic acid were validated and compared in strawberries, tomatoes and apples. In addition, two different reducing agents [dl-1,4-dithiotreitol (DTT) or 2,3-dimercapto-1-propanol (BAL)] were tried for differentiate dehydroascorbic acid and determine vitamin C. Reliability resulted satisfactory for the UV-HPLC methods in each fruit. UV-HPLC methods resulted linear up to 5 mg/100 g and the least detection and quantification limits were <0.18 mg/100 g and <0.61 mg/100 g, respectively. Precision, as relative standard deviation, ranged from 0.6% to 3.9% and the recovery between 93.6% and 104.4%. Although, the UV-HPLC methods resulted useful for the routine analysis of AA and vitamin C in fruits, the best reliability was achieved when using a C18 column and DTT as reducing agent. Moreover, it may be the UV-HPLC method of choice because it is the easiest and cheapest to perform.     

Effect of ascorbic acid and citric acid on the quality of salted Chinese cabbage during storage

Changes in color, browning indices, enzyme activity, and physical and chemical quality during the storage period were investigated to assess the effectiveness of storage period extension along with the addition of ascorbic acid (AA) and citric acid (CA) to salted Chinese cabbage. After 16 days of storage, the change in chromaticity value showed treatment with 0.5% CA showed the lowest change in the brown index during the storage period. The control showed the highest residual activity of polyphenol oxidase among control, AA, and CA-treated salted cabbage. AA and CA treatment effectively inhibited the initial populations of microorganisms including total aerobic bacteria, lactic acid bacteria, and yeast and molds in salted Chinese cabbage during storage. Further, the texture, i.e., hardness, chewability, and elasticity, tended to decrease with increasing storage. These results suggest that treatment with AA could help maintain the quality of salted Chinese cabbage during the storage period.     

Chilling prior to low intensity pulsed electric field processing improved vitamin C stability of carrot purée (Daucus carota cv. Nantes)

Effects of chilling (5 °C) prior to low intensity pulsed electric fields (PEF) (0.1–1.1 kV cm^?1) on vitamin C and activity of peroxidase (POD) and ascorbic acid oxidase (AAO) in carrot purée were studied. The effect of PEF on carotenoids extractability was evaluated and compared to that of purée pre‐conditioned at 20 °C (control). PEF enhanced carotenoids extractability for purée with and without pre‐chilling, up to 25% and 66%, respectively. Vitamin C content decreased after PEF but combined pre‐chilling and PEF maintained vitamin C stability and reduced AAO and POD activities. AAO and the heat‐stable POD fraction were found to be more thermolabile (i.e. higher k_ref value) after PEF, particularly at 0.6 kV cm^?1, which implies elimination of their enzymatic action towards oxidation of bioactive compounds. It was suggested that chilling prior to low intensity PEF modified enzyme properties and secured the stability of vitamin C and carotenoids.     

Effect of carrot (Daucus carota) antifreeze proteins on texture properties of frozen dough and volatile compounds of crumb

The effects of concentrated carrot protein (CCP) containing 15.4% (w/w) carrot (Daucus carota) antifreeze protein on texture properties of frozen dough and volatile compounds of crumb were studied. The sensory quality and texture profile analysis results of bread with CCP supplementation were similar to those of the control. Meanwhile, CCP supplementation brought some beneficial effects in holding the loaf volume. Results of texture property analysis showed that the hardness of dough with CCP supplementation was softer and steadier than that of the control during frozen storage, mainly due to the lower freezable water content. Furthermore, solid phase micro-extraction (SPME)-GC-MS analysis showed CCP supplementation did not give negative influence on volatile compounds of crumb and brought a pleasant aroma felt like Michelia alba DC by trans-caryophyllene simultaneously. In conclusion, CCP could be used as a beneficial additive to frozen dough.     

Effect of thermal treatment and storage on the stability of organic acids and the functional value of grapefruit juice

The effect of conventional and microwave pasteurisation on the main bioactive compounds of grapefruit juice and their stability during 2 months’ refrigerated and frozen storage was evaluated. Ascorbic acid (AA), vitamin C and organic acids were analysed by HPLC, whereas total phenols and antioxidant capacity (%DPPH) were measured by spectrophotometry. The results showed that conventional treatment led to a significant decrease in citric acid (from 1538 to 1478 mg/100 g) and AA (from 36 to 34.3 mg/100 g), whilst microwave pasteurisation preserved these compounds. Frozen storage maintained AA and vitamin C, especially in treated samples. Frozen non-treated samples and conventional pasteurised ones preserved about a 75% and 20% of the total phenols and antioxidant capacity, respectively, whilst in frozen microwave pasteurised juices this preservation was of 82% and 33%. From these results, the use of microwave energy may be proposed as an alternative to traditional heat pasteurisation in order to preserve the natural organoleptic characteristics and essential thermolabile nutrients of grapefruit juice.     

Improvement of shelf-life of buffalo meat using lactic acid, clove oil and vitamin C during retail display

Buffalo meat steaks dipped in either (1) distilled water (control), (2) lactic acid (LA), (3) LA + clove oil (clove), or (4) LA + clove + vitamin C (Vit C) were displayed at 4 ± 1 °C, illuminated by a standard fluorescent lamp. The pH, 2-thiobarbituric acid reactive substances (TBARS), instrumental colour (CIE L^∗, a^∗, b^∗), aerobic plate counts (APC), psychrotrophic counts (PPC), coliform counts and sensory colour and odour were determined up to 12th day of display at 3 days interval. Results showed that, all the treatments have significantly (P < 0.05) reduced the TBARS values compared to control. Among treatments, use of LA + clove has exhibited significantly (P < 0.05) lowest TBARS values throughout display period than others. Buffalo meat steaks treated with either LA + clove or LA + clove + Vit C had significantly (P < 0.05) lower APC, PPC and coliform counts than control or LA treated samples. LA + clove + Vit C treated samples maintained significantly (P < 0.05) higher a^∗ and b^∗ values during display as well as improvement in sensory colour and odour than others. Treatment with either LA + clove or LA + clove + Vit C extended the display life of buffalo meat steaks at 4 ± 1 °C. There appears to be a significant advantage to using LA + clove or LA + clove + Vit C over LA alone.     

Color stability of pumpkin (Cucurbita moschata, Duchesne ex Poiret) puree during storage at room temperature: Effect of pH, potassium sorbate, ascorbic acid and packaging material

The color stability of pumpkin (Cucurbita moschata, Duchesne ex Poiret) puree of pH 4.00 and 5.00 containing potassium sorbate (KS), ascorbic acid (AA) or their mixture, packaged in polyethylene and in polyvinyl chloride-polyvinylidene chloride copolymer (PCPC) bags, was analyzed throughout the storage at 25 °C. Color changes were measured through lightness (L), redness (a), yellowness (b). Changes in a and b were mathematically modeled. In general, lightness, redness and yellowness diminished with storage time. The presence of KS diminished color loss of purees packed in PCPC bags and increased the discoloration of purees contained in polyethylene suggesting, in the first case, that KS oxidation diminished the available oxygen protecting carotenoids oxidation, and in the second case, the existence of a coupled oxidation between KS and carotenoids helped by the oxygen presence. Addition of AA to a puree of pH 4.00 containing KS and packed in polyethylene minimized the losses of redness and yellowness; probably as a consequence of the antioxidant action of AA. The increase in pH from 4.00 to 5.00 in the presence of KS significantly minimized color degradation of puree packed in PCPC. From the point of view of improving color stability, a convenient formulation could be a puree of pH 5.00 preserved with KS and packed in PCPC.     

乳酸对多酚氧化酶活性与构象的影响

以蘑菇多酚氧化酶(PPO)作为原料,研究了不同浓度的乳酸对PPO的相对酶活性、巯基含量、内源荧光强度和紫外强度的影响。结果表明:PPO的相对酶活性随着乳酸处理的浓度增大而减小,当乳酸浓度达到40mmol/L时,其相对酶活性下降到原酶的1.20%,PPO活性得到基本抑制;随乳酸浓度的增大,巯基含量逐渐减小,当乳酸浓度为30mmol/L时,巯基含量为原酶的81.59%;PPO相对酶活性由100%变化到0.17%时,其相对巯基含量从100%降低为80.09%,二者呈现较好线性关系(R2=0.9861);从紫外吸收光谱和荧光发射光谱的变化可以看出:经不同浓度乳酸处理过后PPO分子发生部分去折叠化,导致酶活性的降低。      

Juice matrix composition and ascorbic acid fortification effects on the phytochemical,antioxidant and pigment stability of açai (Euterpe oleracea Mart.)

The effects of juice matrix composition on the phytochemical stability of açai (Euterpe oleracea Mart.) were evaluated by contrasting natural clarified juice systems with isolated polyphenolic and anthocyanin fractions, in the presence or absence of ascorbic acid (500 mg/l) under accelerated storage conditions (37 °C). Polyphenolic (anthocyanin and non-anthocyanin polyphenolics) and anthocyanin fractions were isolated using C18 Sep-Pak columns and then re-dissolved in the original aqueous juice matrix (unbound fraction) or in a citric acid buffer (pH 3.5). The isolation of anthocyanins from the açai matrix improved their colour stability but a greater retention of non-anthocyanin polyphenolics and antioxidant properties was favoured by the initial juice composition. The presence of non-anthocyanin polyphenolics exerted a protective effect against ascorbic acid oxidation and enhanced polyphenolic and antioxidant stability in isolates fortified with ascorbic acid. However, all isolates obtained from açai experienced significant colour, polyphenolic, and antioxidant losses during storage and this indicated that optimization of early stages of industrial processing, storage and distribution are necessary to retain the functional properties of açai-containing products.     

An investigation of rancidity inhibition during frozen storage of Wels catfish (Silurus glanis) fillets by previous ascorbic and citric acid treatment

The effect of preliminary ascorbic and citric acid (AA and CA, respectively) soaking treatments on the rancidity development in Wels catfish ( Silurus glanis ) fillets during further frozen storage (−18 °C; up to 6 months) was studied. Rancidity development was measured by biochemical quality indices (formation of free fatty acids, peroxides and secondary oxidation products) and compared with sensory analysis (appearance, rancid odour and consistency) and general chemical analyses (pH, expressible moisture and heme iron contents). When compared with control samples, AA- and CA-treated samples showed a lower ( P  < 0.05) formation of primary and secondary lipid oxidation compounds that was corroborated by a longer ( P  < 0.05) shelf-life time as a result of a lower rancid odour formation. According to these results, control samples showed a higher ( P  < 0.05) heme iron breakdown (months 3–6) and a lower ( P  < 0.05) water-holding capacity (higher expressible moisture value) (month 6).     

Effects of mechanical handling,storage on ice and ascorbic acid treatment on lipid oxidation in cultured Newfoundland blue mussel (Mytilus edulis)

Lipid oxidation of cultured blue mussels (Mytilus edulis) during mechanical handling and storage on ice was investigated. Furthermore, the exposure of blue mussels to ascorbic acid (Asc) as an antioxidant and its effects on lipid oxidation of sample was monitored. Thiobarbituric acid reactive substances (TBARS) of stored mussels were significantly (p < 0.05) higher than those of the fresh mussels. Mechanical handling of mussels, which includes washing, sorting and packaging, for up to 1 h did not affect their oxidative status significantly (p < 0.05). Furthermore, exposing live mussels to specific concentrations of Asc retarded lipid oxidation significantly (p < 0.05) during storage on ice for only 5 days, after which the Asc became a pro-oxidant.