Modeling Wound-induced Respiration of Fresh-cut Carrots (Daucus carota L.)

ABSTRACT A mechanistic model based on synthesis and inactivation of enzymes, associated to the respiration pathway, was proposed to describe wound-induced respiration of fresh-cut produce. Carrots ( Daucus carota L.) were cut into slices, sticks, a combination of both, and shreds to obtain different wounding intensities, defined by the ratio of new area created to tissue weight (A/W). Respiration rates obtained at 10°C showed a typical increase, a maximum peak, and a decrease until reaching steady state. A 2-phase exponential decay equation described the process, with the obtained key parameters relating to A/W. This model can be used to understand wound-induced respiration and the possible implications in produce quality changes and packaging design.     

Effect of Sodium Chloride, Acetic Acid, and Enzymes on Carotene Extraction in Carrots (Daucus carota L.)

ABSTRACT: Carrot root cores were cut off longitudinally and treated with NaCl (0.6 and 1.2 M ) and/or acetic acid (1.33%, 2.67%, and 4%) solutions. The extractability of the carotenes was estimated. Similarly, carrot cores were also treated with some degrading enzymes (carbohydrases, lipases, and proteases) alone or in combination to study the effect of the tissue rupture or the hydrolysis of possible complexes or interactions between carotenes and other components on the carotene extractability. The results showed that acetic acid increased the extractability of α- and β carotenes up to 99.8% and 94.6%, respectively, at a 4% acid concentration compared with the samples without any treatment. This increase was directly proportional to the acid concentration. An increase in extractability was also observed for NaCl, although the increases were not as high as in the previous case with values of 49% and 41.4% for α- and β-carotenes respectively at a 0.6 M concentration. The study of microstructural changes and extractability revealed that the enzymatic treatments could have broken some carotene complexes and interactions and altered the carbohydrate matrix structure, increasing to a certain extent the extractability of carotenes. It can be concluded then that pickling with 4% acetic acid is a good method to increase the extractability of α- and β-carotenes.     

Sulfite and Starch Affect Color and Carotenoids of Dehydrated Carrots (Daucus carota) during Storage

Sulfite and starch treatments influenced the quality of dehydrated carrots. Initially, redness of dehydrated carrots was high in sulfite-treated samples. Redness and total α- and β-carotenes decreased as storage time increased in all treatments. Starch-treated samples had a slower rate of carotene loss, and retained more (P < 0.05) red color than did control and sulfite-treated samples. When residual sulfite in dehydrated carrots decreased to ～≤200 ppm, its effectiveness in protecting carotene was not notable.     

微波提取对胡萝卜中的多糖基本结构特征及固体形貌的影响

研究微波提取对胡萝卜中的多糖基本结构特征及固体形貌的影响。采用沸水浴、微波两种方式提取胡萝卜中的多糖(分别记为WEP和MEP),通过基本理化性质测定、高效体积排阻色谱(high performance size exclusion chromatography,HPSEC)和单糖组成分析等方法比较了两者的基本结构特征,并采用扫描电子显微镜对两者的固体形貌进行表征。结果显示,WEP和MEP的中性糖、糖醛酸和总酚含量存在差异,两者均由半乳糖醛酸、半乳糖、葡萄糖、阿拉伯糖、鼠李糖组成,但MEP总糖含量更高并含有更多果胶类单糖;WEP和MEP的HPSEC图有一定相似性,但WEP中含有重均分子质量高达7.77×105 D的组分;WEP表现较为聚集的片状结构,而MEP组分则表现较为分散且主要为小片段状态。上述结果表明,两种不同提取方法所得到的多糖具有显著差异。     

Optimization of enzymatic process parameters for increased juice yield from carrot (Daucus carota L.) using response surface methodology

The effects of enzyme concentration (50–650 mg/kg grated carrot), pectolytic and cellulolytic enzyme ratio (3:7–7:3), incubation time (30–150 min) and temperature (25–65 °C) on juice recovery and viscosity from grated carrot were studied. A central composite rotatable design (CCRD) was used in designing the treatment combinations of four variables at five levels. The process involved in treating the blanched grated carrot with mixture of crude pectolytic enzyme from Aspergillus foetidus and crude cellulolytic enzyme from Trichoderma ressi, keeping the samples at the desired time, followed by extraction of juice. Enzyme-treated grated carrot sample showed increased juice recovery as compared to control. A second-order response surface model adequately fitted the data. All the variables affected juice recovery and viscosity significantly. Enzyme concentration, pectolytic and cellulolytic enzyme ratio, incubation time and temperature had total and combined effect at linear, square and interactive level on both responses. The optimum condition was enzyme concentration, 210.7 mg/kg of grated carrot; pectolytic and cellulolytic enzyme ratio, 3.84:6.16; incubation time, 130 min and incubation temperature 47 °C. Under the optimal conditions, juice extracted from enzyme-treated grated carrot was 74.3% having juice viscosity 1.07 cP, corresponding to the increase in yield by 13.95% and decrease in viscosity by 0.45 cP.     

Purification and characterisation of carrot (Daucus carota L) pectinesterase

A pectinesterase isoform with an alkaline isoelectric point of over 8.66 was detected in crude extracts of carrot. The enzyme was purified by ion exchange and molecular exclusion chromatography. The molecular weight of the isoform was 25 kDa, determined in native conditions by filtration through Sephadex G‐75 SF. The enzyme showed a high affinity for its substrate, with K_m and V_max values of 0.031 mg ml^?1 and 6.77 units respectively for apple pectin. The pectinesterase activity exhibited an optimum around pH 7.4 and was activated by metallic ions, with optimum activities at NaCl concentrations between 130 and 330 mM and at CaCl₂ concentrations between 15 and 50 mM . The enzyme was activated most by Ca²⁺ and exhibited a greater tolerance of high concentrations of Na⁺. Comparison of its heat stability with other pectinesterases of vegetable origin indicated that the purified isoform was very thermolabile, being rendered inactive by heating for 5 min at 70 °C. The enzyme was inhibited by high concentrations of polygalacturonic acid and competitively inhibited by D ‐galacturonic acid, with a K_i value of 1 mM . Copyright © 2003 Society of Chemical Industry     

Effects of Genotype, Root Size, Storage, and Processing on Bioactive Compounds in Organically Grown Carrots (Daucus carota L.)

ABSTRACT: The effects of genotype, root size, storage, and processing on the content of bioactive compounds in carrots were determined to investigate the possibilities for optimizing the health-promoting properties of this vegetable. The content of polyacetylenes (falcarinol, falcarindiol, falcarindiol-3-acetate), carotenoids (α-and β-carotene), and isocoumarin 6-methoxymellein (6-MM) varied significantly between 6 genotypes of the Nantes type. The content of falcarindiol, falcarindiol-3-acetate, and 6-MM was significantly higher in small (50- to 100-g root size) than in extra large root sizes (>250-g root size). Refrigerated storage of the roots for 4 mo at 1 °C before processing resulted in a significantly higher content of polyacetylenes and no differences in the content of carotenoids and 6-MM compared with frozen storage of processed carrots. The content of falcarinol increased and that of falcarindiol and falcarindiol-3-acetate decreased during steam blanching of the carrots before freezing. No changes were observed in the content of carotenoids and 6-MM.     

Texture and Histological Structure of Carrots Frozen at a Programmed Rate and thawed in an Electrostatic Field

To investigate the most suitable rate of freezing and method for thawing, raw and blanched carrots were frozen with LN₂ (freezing rate: –5°or -2°C/min, final temp: -30°C) using a program freezer (PF), or were frozen using conventional freezers (F: -80°C, -30°and -20°C). Then, they were thawed in five different ways: electrostatic thawing (ET, -3°C, 17 hr); -3°C, 17 hr; 5°C, 17 hr; 20°C, 30 min; 100°C, 3 min. Firmness of thawed carrots and amount of undamaged tissues by LM and TEM observations were greatest to least: PF -5°C/min < PF-2°C/ min <-80°C CF<-30°CF<-20°CF, and ET ≧-3°< 5°< 20°< 100°C, respectively. Results suggest the optimum rate of freezing was -5°C/ min. The frozen disks were defrosted comparatively fast even at -3°by ET. Drip, cell damage and softening of disks were prevented by ET.     

Effects of washing and packing on sensory and chemical parameters in carrots (Daucus carota L)

Carrots washed and packed by hand or machine and stored at 2, 10 or 20 °C in three different package types were analysed for taste, flavour and content of sugars, terpenes, 6‐methoxymellein and ethanol as well as for ethylene, CO₂ and O₂ concentrations in the packages. Carrots washed by machine had increased micro‐organism decay and higher sensory scores for bitter taste, aftertaste, terpene flavour and odour, green odour and earthy flavour. The ability of packages to ventilate was important to avoid anaerobic conditions that caused decreased sucrose content, increased production of ethanol and a higher intensity of ethanol flavour and sickeningly sweet taste. Increasing temperature enhanced the concentration of ethanol, CO₂ and ethylene and decreased the O₂ concentration as well as the content of sucrose and total sugar. High temperature also increased the intensity of ethanol flavour and odour, aftertaste, earthy flavour, terpene flavour and bitter taste. Bitter taste was positively correlated with 6‐methoxymellein level, although this level was below the sensory threshold. Bitter taste, earthy flavour and aftertaste were correlated with total terpenes and several individual terpenes. Carrots washed and packed early in the long‐term storage period (November) were more bitter and had a higher level of 6‐methoxymellein and a higher intensity of terpene flavour and odour, green flavour and earthy flavour than those handled in January or March. Copyright © 2004 Society of Chemical Industry     

Effects of limonene on the growth and physiology of cabbage (Brassica oleracea L) and carrot (Daucus carota L) plants

Monoterpenes are plant‐based alternatives for pest control in sustainable agriculture. This study investigated the phytotoxic effects of the monoterpene limonene on white cabbage (cv Rinda and Lennox) and carrot (cv Parano and Splendid) plants. The effects of increasing concentrations (from 10 to 120 ml l^?1) of limonene on visible leaf injuries, growth, chlorophyll fluorescence, net photosynthesis and stomatal conductance were studied. Limonene concentrations of 90 and 120 ml l^?1 were significantly phytotoxic in both cabbage and carrot, depending on the cultivar. However, there were major differences in limonene responses between the cultivars in both species. In carrot, lower shoot and root biomass was related to lower chlorophyll fluorescence (indicating lower efficiency of the photochemical processes) in cv Splendid, whereas in cv Parano it was related to lower stomatal conductance (indicating reduced gas exchange), suggesting that the mechanism behind the phytotoxicity may be different in different cultivars. In cabbage, better limonene tolerance and faster recovery processes in cv Lennox compared with cv Rinda were evident through increasing efficiency of photochemistry (chlorophyll fluorescence), and in the higher stomatal conductance and net photosynthesis rates, providing energy for defence and repair action. Since direct phytotoxic effects were detected on carrot and cabbage with limonene, we conclude that critical threshold concentrations for cultivated plants should be determined before monoterpenes are widely used as repellents and deterrents. These thresholds should, as far as possible, be species‐ and cultivar‐specific in order to provide full protection of plants. Copyright © 2004 Society of Chemical Industry     

Effects of High Pressure on Texture and Microstructure of Sea Bass (Dicentrarchus labrax L.) Fillets

High pressure is an innovative non‐thermal food‐preservation technology. We studied the effect of high‐pressure treatment up to 500 MPa for 5 min on physical characteristics of sea bass fillets after 0, 7, and 14 d of refrigerated storage. Color results exhibited an increase of lightness and a slight change of hue, which might be imperceptible in cooked fish. High‐pressure treatment induced a decrease of exudation and water‐holding capacity. Pressure treatment above 300 MPa provoked higher fish hardness after storage than in untreated sample, proving the ability of high pressure to improve textural quality of chilled, stored fish fillet. These assessments were corroborated with microstructure observations. We showed that high‐pressure treatment at 500 MPa allowed, after 7 d of storage, a total aerobic count equivalent to that of untreated fresh fish fillet to be obtained. Thus, high pressure might be considered to be a technology able to improve safety and textural quality of fresh fish fillets.     

Radiation Processing of Minimally Processed Carrot (Daucus carota) and Cucumber (Cucumis sativus) to Ensure Safety: Effect on Nutritional and Sensory Quality

ABSTRACT: In the present study, radiation processing of minimally processed carrot and cucumber at a dose of 2 kGy was carried out. The effect of this treatment on different quality parameters such as vitamin C content, total carotenoids content, sensory quality, texture, and color was determined over a storage period of 16 d at 8°C to 10° C. In the case of cucumber, treatment of irradiation as well as storage period showed no significant change in the total vitamin C content of either the control or the irradiated samples. In the case of carrots, a 2-kGy dose had no significant effect ( P < 0.05) on total vitamin C content of the samples. However, during storage, both control as well as irradiated samples showed significant decrease ( P < 0.05) in vitamin C content. Total carotenoids content in carrot remained almost unchanged after irradiation as well as during storage. Sensory evaluation results showed that irradiation had no significant ( P < 0.05) effect on the ratings of any of the sensory attributes in carrot. Radiation processing of cucumber affected the flavor significantly. However, this change did not alter the overall acceptability of cucumber. Textural studies revealed that in both carrot and cucumber, there was no significant change ( P < 0.05) in firmness of the central region after irradiation, whereas the peripheral region in carrot showed significant reduction in firmness. In the case of cucumber, there was no significant change ( P < 0.05) in the texture of both peripheral regions. However, during storage, the peripheral regions of carrot and cucumber showed significant increase in firmness. Color measurement results indicated no drastic change in color coordinates of carrot samples. Thus, the nutritional as well as sensory quality of minimally processed foods did not alter significantly after gamma irradiation.     

On the induction of cold acclimation in carrots (Daucus carota L.) and its influence on storage performance

We investigated the role of cold acclimation in carrot plants with respect to its influence on the storage performance of the harvested taproots. The induction of cold acclimation was followed in plants cultivated in a growth chamber under strict climate control and in taproots harvested from two separate field cultivations where the plants had been exposed to the natural variations in climate. Under controlled growth conditions, levels of antifreeze protein (AFP) mRNA were used as a marker for cold acclimation in carrot taproot tissue. Expression of this gene was induced by cold in discs excised from harvested taproots and this induction was clearly affected by the growth temperature of the plants from which the taproots were taken. These in vitro data were consistent with those from field-grown plants. In the cell wall of taproots harvested in year 2000, where the intact plants had frequently been exposed to temperatures below 6 °C, a 36 kDa AFP accumulated to higher levels during storage than in the taproots harvested from plants grown in year 2001, where cultivation temperatures had rarely dropped below 6 °C. The taproots from 2001 exhibited poor storage performance as shown by an earlier increase in relative electrolyte leakage and decrease in dry matter compared to taproots harvested in 2000. The capacity of the AFP to accumulate during storage was consistent with a high storage performance.     

Polyacetylenes in fresh and stored carrots (Daucus carota): relations to root morphology and sugar content

BACKGROUND: Carrot roots contain polyacetylenes, reported to be both beneficial and distasteful when consumed by humans. This study aimed to investigate the relationships between polyacetylene contents, root morphology and sugar content in order to increase the opportunities to optimise the composition of polyacetylenes in carrots. RESULTS: The falcarinol/total polyacetylene ratio was positively correlated with root size, the amount of sucrose and the sucrose/total soluble sugar ratio among both fresh and stored samples. Root size was inversely correlated with the amounts of falcarindiol and falcarindiol‐3‐acetate, especially among stored samples. Stored carrots exhibited an inverse correlation between polyacetylenes and the amount of soluble sugar. At a falcarinol content at harvest below approximately 200 mg kg^?1 dry weight the amounts of all polyacetylenes increased during storage, but above that level the amounts of all polyacetylenes instead decreased. CONCLUSION: The results indicate similarities in the activity of the enzymes transforming sucrose to hexoses and the enzymes transforming falcarinol to falcarindiol‐3‐acetate and falcarindiol. The negative correlation between root size and polyacetylenes seems to be partly due to dilution but also to a higher synthetisation rate in smaller roots. The results indicate the existence of an equilibrium regulating the level of falcarinol. Copyright © 2011 Society of Chemical Industry     

Nutritional, Physical, and Sensory Evaluation of Hydroponic Carrots (Daucus carota L.) from Different Nutrient Delivery Systems

ABSTRACT:  Carrot ( Daucus carota  L.) has the highest carotenoid content among foods and is consumed in large quantities worldwide, while at the same time its market demand continues to increase. Carotenoids have also been associated with protective effects against cancer and other chronic diseases. The most predominant carotenoids in carrots are β- and α-carotenes. Moisture, ash, fat, texture, color, carotene content, and consumer acceptance of carrots grown in a hydroponic system with nutrient film technique (NFT) and microporous tube membrane system (MTMS) were evaluated. The moisture contents of the NFT- and MTMS-grown carrots ranged from 86.8 ± 0.13% to 92.2 ± 2.25% and 80.9 ± 0.31% to 91.6 ± 1.01%, respectively. Fat and ash contents of the carrots were negligible. NFT-grown Oxheart had the most β-carotene (9900 ± 20 μg/100 g) while Juwaroot had the least (248 ± 10 μg/100 g). However, the β-carotene content of Juwaroot from the NFT batch II carrots was 3842 ± 6 μg/100 g. MTMS-grown carrots had less variation in the total β-carotene contents (2434 ± 89 to 10488 ± 8 μg/100 g) than those from NFT. Overall, Nantes Touchan (4.8 ± 2.3) and Nevis-F (7 ± 1.4) from NFT were the least and most preferred by consumers. Mignon was also acceptable to consumers, and significantly ( P  < 0.05) more preferred than the other carrots in that NFT batch. MTMS-grown Kinko and Paramex, which were significantly ( P  < 0.05) more preferred than Nandrin-F and the commercial field-grown carrot, were equally liked by consumers. Nevis-F, Mignon (NFT), Paramex, and Kinko (MTMS) are potentially good cultivars to be included in NASA's food system.     

Sensory and chemical changes in five varieties of carrot (Daucus carota L) in response to mechanical stress at harvest and post‐harvest

Carrots harvested by hand or machine and given additional mechanical stress by shaking in a transport simulator were analysed for taste, flavour and content of sugars, terpenes, 6‐methoxymellein and ethanol as well as for ethylene production and respiration. Carrots stressed by shaking had higher ethylene production and respiration, higher content of ethanol and 6‐methoxymellein and lower levels of total terpenes, several individual terpenes and sugars. This corresponded to a higher sensory score for ethanol flavour and odour, bitter taste, earthy flavour, terpene flavour, aftertaste and sickeningly sweet taste and a lower score for acidic taste and sweet taste as measured by an expert taste panel. Ethanol content was highly correlated with ethanol flavour and odour and sickeningly sweet taste. Of five varieties tested, ‘Bolero’ ‘Panter’ and ‘Yukon’ were most sensitive to mechanical stress, whereas ‘Napa’ and ‘Newburg’ were most resistant. Hand‐harvested carrots were not significantly different from machine‐harvested carrots as regards chemical or sensory variables. Principal component analysis showed only slightly different placing of these samples in the score plot. A digital carrot could monitor the degree of mechanical stress to which the carrots were subjected. © 2001 Society of Chemical Industry     

Panelist Texture Preferences Affect Sensory Evaluation of Green Bean Cultivars (Phaseohs vulgaris L.)

The effects of textural preferences on sensory intensity and hedonic scores assigned by consumer panelists (50 preferred “soft” and 38 “crisp” beans) to green beans (Phaseolus vulgaris L.) of two cultivars cooked by 2 methods were studied. Boiled and 'Strike’beans were rated lighter than steamed and‘Mustang’beans.‘Mustang’beans were scored more acceptable for color, flavor, and overall likability. Soft textural preference panelists liked steamed beans less than boiled beans for texture, flavor, and overall likability. Hedonic scores assigned by panelists of crisp textural preference did not differ by preparation method. Selecting panelists without considering textural preferences may influence hedonic but not intensity scores.