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.     

Comparison of Vacuum Treatments and Traditional Cooking Using Instrumental and Sensory Analysis

The purpose of this work was to compare carrots with similar firmness cooked by traditional cooking and two vacuum treatments: sous-vide (SV) and cook-vide (CV). As a first step, consumers determined the preferred level of firmness for carrots cooked by traditional cooking (boiling). This level corresponded to instrumental firmness of 2.8 N in phloem tissue and 4.1 N in xylem tissue. Response surface methodology (RSM) established the pairing conditions of time (22 to 78 min) and temperature (78 to 92 °C) to study the effect of both factors on the firmness of carrots with sous-vide and cook-vide treatments. In both treatments, the instrumental firmness of phloem and xylem samples was measured and modeled. No significant differences were found in firmness values between phloem and xylem tissue of samples cooked by vacuum treatments (CV and SV). For CV treatment, firmness decreased linearly with time and temperature, while for SV treatment it followed a second-order model. Based on the model, conditions of time and temperature to achieve the preferred firmness (2.8 N) were selected for both treatments. Finally, consumers compared the sensory properties of carrots cooked by traditional cooking, sous-vide, and cook-vide with paired comparison tests evaluating three pairs of samples. Carrots cooked by cook-vide were considered less tasty than sous-vide and traditional cooking carrots. Carrots using traditional cooking were firmer than those obtained with SV and CV treatments. Carrots cooked by traditional and sous-vide treatments were preferred to cook-vide ones for the taste.     

Comparison of the quality of sous-vide and conventionally processed carrots

 The quality of "sous-vide" and conventionally processed carrots was evaluated by sensory analysis. Furthermore, changes in colour, odour, taste and texture of the "sous-vide" products during storage over 21 days at 2  °C were determined with instrumentation. According to the panel's evaluation, the sensory quality of the "sous-vide" processed carrots remained almost constant over the storage period. However, the shear force values indicated a strengthening of the texture. The colour changed from typical orange to red-orange. A slight decrease of the flavour and aroma intensity was recorded by the panel, which was confirmed by the data gained with the Electronic nose and the AromaScan. The sous-vide processed products were always preferred and therefore obtained a higher valuation even at the end of storage. In contrast to the conventionally processed carrots, only a slight reduction in the content of sucrose, fructose and glucose was determined for the sous-vide product. Received: 3 February 1998 / Revised version: 17 April 1998     

Use of high pressure to reduce cook loss and improve texture of low-salt beef sausage batters

Methods were investigated to reduce the salt content of beef-containing smallgoods as high-salt intake has been identified as a public health risk for most individuals. Raw meat batters were manufactured from retail beef mince (4–7% fat) using various NaCl concentrations (0–2%), and were packed into casings and subjected to high pressure processing (up to 400 MPa for 2 min at 10 °C). Following pressure treatment, samples were cooked to an internal temperature of 72 °C and cooled. Cooked products were assessed for cooking loss, colour and physical consistency by texture profile analysis. Flavour and overall acceptability were assessed by sensory panels. High pressure processing (HPP) was found to produce a dramatic improvement in the moisture retention of the cooked products. Control (unpressurised) sausages containing 2% NaCl had a similar cook loss (9.3%) to pressure-treated sausages containing just 1% NaCl, whereas unpressurised samples with 1% NaCl had a cook loss of 24.9%. The hardness and gumminess of pressure-treated samples was higher compared to untreated samples, at all salt concentrations. The greatest differences in texture with pressure treatment were seen in the 1% NaCl samples. Pressure treatment generally caused no changes in the colour of either the raw or cooked product; however there was a slight increase in “whiteness” with pressure treatment. Sensory panels reported a greater acceptability in both appearance and texture of pressure-treated sausages of lower salt content compared with non-pressure-treated samples. Examination of extracted proteins using SDS-PAGE and of muscle proteins by thermal analysis indicated that pressure contributed to enhanced binding through protein solubilisation and gelation through partial protein unfolding. The application of high pressure to beef sausages with low-salt content resulted in reduced cooking losses and improved texture.

Industrial relevance

Enhanced meat binding through extraction of salt-soluble proteins is an essential step in the formulation of meat products such as sausages and emulsion-type products. The ability to reduce salt and achieve high binding and water retention through use of HPP is important in being able to produce healthier foods.     

Effects of different cooking methods on the chemical and physical properties of carrots and green peas

The study was aimed to evaluate the physicochemical effects of three cooking methods i.e. sous-vide (SV), cook-vide (CV) and traditional cooking (TC) on carrots and green peas. SV and CV were performed at 60–90 °C for various time periods (SV: green peas 50–100 min, carrots 90–150 min; CV: green peas 30–70 min, carrots 20–60 min) with respect to peroxidase test. These vegetables were also cooked at atmospheric pressure for 15, 30, 45 and 60 min and the results were compared with those obtained from SV and CV. Antioxidant activity, total phenolic and vitamin C analyses reflected less harm to the green peas in CV as compared to SV and TC. However, carrots were approximately half degraded during SV than in CV and TC as shown by the antioxidant activity. Moreover, total phenolic content of carrots was highly protected when cooked in SV method. The color change values (∆ E) of green peas were slightly lower in TC when compared to CV and SV, while in carrots, they were very close to each other's in all three methods. CV-cooked green peas and carrots provided the highest general acceptance for the sensorial properties. As a conclusion, TC had more adverse effects on the quality characteristics on green peas and carrots.     

Comparison of the quality of sous-vide and conventionally processed carrots

 The quality of "sous-vide" and conventionally processed carrots was evaluated by sensory analysis. Furthermore, changes in colour, odour, taste and texture of the "sous-vide" products during storage over 21 days at 2  °C were determined with instrumentation. According to the panel's evaluation, the sensory quality of the "sous-vide" processed carrots remained almost constant over the storage period. However, the shear force values indicated a strengthening of the texture. The colour changed from typical orange to red-orange. A slight decrease of the flavour and aroma intensity was recorded by the panel, which was confirmed by the data gained with the Electronic nose and the AromaScan. The sous-vide processed products were always preferred and therefore obtained a higher valuation even at the end of storage. In contrast to the conventionally processed carrots, only a slight reduction in the content of sucrose, fructose and glucose was determined for the sous-vide product. Received: 3 February 1998 / Revised version: 17 April 1998     

Salt (NaCl) reduction in cooked ham by a combined approach of high pressure treatment and the salt replacer KCl

The food industry must develop effective methods to address the reduction of salt in meat products and contribute to the reduction of salt consumption associated with cardiovascular diseases. This paper investigated the effect of NaCl content (0, 0.95, 1.33 and 1.90%), phosphate content (0 and 0.25%) and the use of high pressure processing (HPP) (100, 300, 600 MPa) at different processing stages (raw material, after injection, tumbling and cooking) on the quality parameters (cooking loss, texture, water holding capacity, color and saltiness perception) in cooked ham. The application of HPP to the raw meat or after its injection was detrimental to the structure and water retention of the salt-reduced cooked ham. Whereas the application of HPP at 100 MPa after tumbling was beneficial. A further salt reduction up to 1.1% NaCl was possible by the salt replacement with KCl (0.2%) in combination with the HP treatment.Industrial relevanceHigh-pressure treatment can help in the production of salt-reduced meat products but efforts are needed to understand the feasible levels of NaCl, phosphates and specific HP treatments to apply in commercial scenarios. The present paper describes a strategy to produce a salt-reduced cooked ham (45% reduction) using a HP treatment at 100 MPa after tumbling stage in combination with KCl (0.2%).     

Release and absorption of carotenes from processed carrots (Daucus carota) using in vitro digestion coupled with a Caco-2 cell trans-well culture model

The release and absorption (bioavailability) of carotenoids is a prerequisite for their nutritional impact. This can be strongly affected by the processing conditions used to prepare the food matrix that contains them. To determine the effect of processing on carotenoid bioavailability, homogenized, raw, blanched and cooked carrots were exposed to an in vitro gastric and intestinal digestion model. Final digest samples were placed onto a Caco-2 cell trans-well monolayer culture to mimic intestinal absorption. The results show that the cooked carrot puree consisting of primarily single plant cell particles had the highest release of carotenes, followed by blanched consisting primarily of plant cell clusters and raw carrot puree consisting of larger plant cell clusters. Absorption through the Caco-2 cell layer was the highest from the digesta of cooked carrot puree followed by the digesta of blanched carrot puree. This study demonstrates that thermal processing and/or mechanical homogenization to disrupt plant cell wall matrix enhances the in vitro bioavailability of carotenes from carrots.     

Factors contributing to taste and quality of commercially processed strained carrots

Commercially processed strained carrots were obtained from three different processing locations over a 1-year span. Selected carrot lots exhibited both desirable and undesirable sensory attributes based on informal evaluations, while additional carrots were chosen based on postharvest storage factors that may have influenced overall quality. Physicochemical analysis was conducted to determine factors influencing carrot taste and color attributes that could be utilized for retail quality assessment. Quantitative sensory analysis was performed on a subset of the production lots representing a diverse range in chemical composition. Basic taste attributes indicated that concentrations of 6-methoxymellein (6-MM), soluble phenolics and organic acids in relation to high moisture content were critical factors for strained carrot taste. Strained carrot color could not be attributed to processing location or chemical composition and was likely due to raw product variation between cultivars. Variation between each processing location was greater than variation within each location, and overall differences between lots was attributed to 6-MM and soluble phenolic acid concentrations. By screening raw carrots for indications of stress induced chemical constituents, an understanding of those factors contributing to commercially processed strained carrot taste can be obtained.     

Role of quantity and quality of fat in meat models inoculated with Listeria innocua or Salmonella Typhimurium treated by high pressure and refrigerated stored

Several variables can influence the effects of high hydrostatic pressure processing (HPP), but the role of fat in the treated sample is still uncertain. We designed a model by which controlling the known variables we could elucidate that role. We applied 400 MPa for 2 min to minced chicken samples inoculated with Listeria innocua and Salmonella Typhimurium mixed with 10% and 20% of three fat types with different fatty acid composition. Microbial counts were performed during 60 days of refrigerated storage either at 2 °C or 8 °C.Immediately after HPP bacterial growth was independent of the type and percentage of fat content, but a possible effect of type of fat could be observed after 60 days of cold storage.     

Ascospore inactivation and germination by high pressure processing is affected by ascospore age

The effects of age on high pressure resistance of the ascospores of heat resistant moulds Byssochlamys fulva, B. nivea, Neosartorya fischeri and N. spinosa were determined. Ascospores were harvested from cultures grown for 3–15 weeks at 30 °C on malt extract agar. Following filtration and determination of concentration, the ascospores were subjected to high pressure processing (HPP) at 600 MPa for 10 min in 0.1 M citrate phosphate buffer (pH 4 and 6) and mango puree (pH 5). The results supported our hypothesis that age (maturity) affects high pressure resistance of ascospores of heat resistant moulds. A reduction of log₁₀ 2.5 cfu mL^− 1 was achieved for three week old ascospores ofB. nivea whereas for nine week old ascospores only a half log reduction was achieved. Similar results were observed for B. nivea and N. fischeri. The HPP treatment caused activation of ascospores of N. spinosa, with older ascospores showing increased activation.

Industrial relevance

The observation of activation of some ascospores by HPP, indicates that HPP alone is insufficient for elimination of these problematic spoilage microorganisms. HPP would need to be combined with other hurdles in order to produce high quality pressure-treated shelf-stable fruit products.     

Comparison of hydrostatic and hydrodynamic pressure to inactivate foodborne viruses

The effect of high hydrostatic pressure (HPP) and hydrodynamic pressure (HDP), in combination with chemical treatments, was evaluated for inactivation of foodborne viruses and non-pathogenic surrogates in a pork sausage product. Sausages were immersed in distilled water, 100-ppm EDTA, or 2% lactoferrin, and then inoculated with feline calicivirus (FCV), hepatitis A virus (HAV) or bacteriophage (MS2, phiX174, or T₄). Each piece was packaged individually and subjected to pressure by either HDP, HPP (500 MPa, 5 min, 4 °C), or control (no pressure). On sausages immersed in water, HPP and HDP significantly (P < 0.05) reduced titers of FCV by 2.89 and 2.70 log₁₀ TCID₅₀/ml, and HAV by log₁₀ 3.23 and 1.10, respectively, when compared to non-pressure-treated controls. Titers of T₄ (1.48 and 1.10 log₁₀ PFU/g) and MS2 (1.46 and 0.96 log₁₀ PFU/g) were also significantly reduced by HPP and HDP treatments, respectively, in combination with water. Inoculation of viruses and bacteriophage on a meat product may have protected viruses from complete inactivation by pressure treatments.

Industrial relevance

This is the first study to directly compare hydrostatic and hydrodynamic pressure technologies to inactivate microorganisms. This is also the first study to examine the inactivation of viruses and bacteriophages by pressure technology in a deli meat product. This study shows that viruses attached to meat surfaces may be protected from complete inactivation by hydrostatic and hydrodynamic pressure treatments, and these findings require more investigation into the survival of viruses in deli meat products.     

Carrots of Many Colors Provide Basic Nutrition and Bioavailable Phytochemicals Acting as a Functional Food

ABSTRACT: Hippocrates, a philosopher who lived from 460 to 359 BC is often quoted as saying, “Let your food be thy medicine and your medicine be thy food.” Having lived just shy of a century at a time when life expectancies were much less, he must have understood the importance of a healthy diet. A diet high in fruit and vegetables has been linked to optimal health in a variety of studies. One vegetable that has gained popularity is the carrot due in part to the introduction of “cut & peel” convenience packages. Although most people in the United States know carrots as an orange vegetable that can be eaten raw or in a variety of cooked dishes, original carrots were yellow and purple. These carrot varieties are currently undergoing phenotypic recurrent selection to improve the profile of compounds considered to be beneficial. This process is called biofortification, which has increased provitamin A content by >40% since 1970. The most novel carrot produced to date is an orange–purple–red variety that not only contains provitamin A activity as α‐ and β‐carotene, but also contains anthocyanins and the nonprovitamin A carotenoid lycopene, of which both are potent antioxidants. A functional food is one that provides benefit beyond basic nutrition. Biofortified carrots of many colors not only provide vitamin A, but may contribute to optimal health. Because supplements have not been shown to be overly beneficial, except for correcting deficiencies, whole food‐based approaches to enhance health by utilizing functional foods such as biofortified carrots should be considered.     

Influence of selected packaging materials on some quality aspects of pressure-assisted thermally processed carrots during storage

Role of packaging barrier properties and storage conditions on pressure-assisted thermally processed (PATP) carrot quality were investigated. Samples were packaged in pouches fabricated using three packaging materials (Nylon/EVOH/EVA, Nylon/EVA and MetPET/PE) and processed at 600 MPa and 110 °C for 10 minutes. Processed pouches were stored at 25 and 37 °C, and withdrawn over 12 weeks. Samples were analyzed for color, β-carotene and total plate count. Oxygen and water vapor transmission rates (OTR, WVTR), melting point and enthalpy of fusion of the packages were evaluated. PATP treatment resulted in product shelf-stability during storage. Packaging type and storage conditions significantly influenced the product color and β-carotene content. Nylon/EVOH/EVA package best preserved carrot quality. PATP increased OTR of the MetPET/PE and degraded carrot color and β-carotene during storage. Raw carrots had 11.13 mg/100g β-carotene content. PATP treatment followed by 12 weeks storage at 37 °C reduced the β-carotene content of carrots packaged in Nylon/EVOH/EVA, Nylon/EVA and MetPET/PE to 7.19, 0.04 and 0.06 mg/100g, respectively. Similarly, the red color of carrot samples (25.51 for raw carrots) decreased to 19.85, 3.44 and 7.20 for Nylon/EVOH/EVA, Nylon/EVA and MetPET/PE, respectively. The study demonstrated the importance of high barrier packaging materials in preserving PATP-treated carrot quality.     

Physicochemical and Microbiological Quality of Sous-Vide-Processed Carrots and Brussels Sprouts

Physical properties, microbiological quality and volatile compounds of sous-vide-processed carrots and Brussels sprouts were analysed after 1, 5 and 10 days of refrigerated storage. Similar analyses were performed on raw and steamed carrots and Brussels sprout for comparison. Sous-vide carrots were firmer than steamed and firmness increased during storage. Similar values of colour indices were obtained for both steamed and sous-vide carrots, which also showed an increase of redness and colour saturation during storage. Aerobic and anaerobic counts of raw carrots were significantly reduced both by steaming and sous-vide procedures at values lower than 1 log cfu/g; these values were maintained until the end of storage. Among volatiles, terpenes were better preserved in sous-vide than steamed carrots, but all volatile fractions were significantly affected during storage. Steamed Brussels sprouts were softer and greener than sous-vide-processed ones, but softening and loss of green of the latter increased under vacuum storage. Microbiological counts of raw products were more efficiently reduced by sous-vide procedures than steaming. Higher amounts of nitriles and terpenes were shown in sous-vide vegetables in comparison to steamed, whereas thiocyanates and isothiocyanates occurred in lower quantities. Volatiles were not affected during 5 days of storage.     

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.     

Impact of frozen storage on polyacetylene content, texture and colour in carrots disks

This study investigated the effect of freezing method (slow or blast freezing) with or without blanching during storage at −20 °C on the levels of three polyacetylenes, falcarinol (FaOH), falcarindiol (FaDOH), falcarindiol-3-acetate (FaDOAc) in carrot disks. The quality of the carrot disks was also assessed using instrumental texture and colour measurements. Blast frozen carrot disks retained higher amounts of polyacetylenes compared to their slow frozen counterparts. Whilst the levels of retention of total polyacetylenes was higher in unblanched than blanched disks prior to freezing there was a sharp decrease in the levels of polyacetylenes in unblanched frozen carrots during the storage period for 60 days at −20 °C. FaDOH was observed to be the most susceptible to degradation during frozen storage of unblanched carrot disks, followed by FaOH and FaDOAc. The changes in the level of polyacetylenes during storage were adequately described by using Weibull model. The texture and colour were also found to decrease during frozen storage compared to fresh carrots.     

Antibacterial potential of Enterococcus faecium strains isolated from sous-vide cooked fish fillets

Nineteen isolates of Enterococcus faecium were isolated from sous-vide cooked cod fillets stored 3-8 weeks at 3°C. Fourteen isolates produced proteinaceous substances inhibitory to different strains of Listeria monocytogenes, other pathogenic bacteria and spoilage bacteria. The isolates had similar growth profiles in broth at 0, 3, and 5°C. In the presence of 10⁷ cfu ml^-1 E. faecium, L. monocytogenes (10² cfu ml^-1) was strongly inhibited at 3°C and partially at 5°C and 15°C. When cultivated with 10⁴ cfu ml^-1 E. faecium, L. monocytogenes (10² cfu ml^-1) was only slightly inhibited at 15°C and not at 3°C or 5°C. Spontaneous resistance phenomena were observed at 15°C after 11 days. The isolates of E. faecium did not produce off-odours in shrimp extracts or sous-vide cooked fish. The potential use of the isolated strains of E. faecium as biopreservation is suggested.     

High pressure processing of cocoyam,Peruvian carrot and sweet potato: Effect on oxidative enzymes and impact in the tuber color

High pressure processing (HPP) is a non-thermal technology used to activate or inactivate enzymes. This study investigated the effects of HPP (600 MPa for 5 or 30 min at 25 °C) on cocoyam, Peruvian carrot and sweet potato color, and the polyphenoloxidase (PPO) and peroxidase (POD) activities in tuber cubes, puree, and enzyme extract subjected to HPP. The results showed enzyme inactivation by HPP in cocoyam (up to 55% PPO inactivation in puree and 81% POD inactivation in extract) and Peruvian carrot (up to 100% PPO and 57% POD inactivation the extract). In contrast, enzyme activation was observed in sweet potato (up to 368% PPO and 27% POD activation in puree). The color results were compatible to enzyme activity: the color parameters remained unchanged in cocoyam and Peruvian carrot, which showed high PPO and POD inactivation after HPP. Furthermore, the impact of HPP on the enzymes was influenced by the matrix in which HPP was carried out, evidencing that the enzyme structure can be protected in the presence of other food constituents.Industrial relevanceThe enzymes PPO and POD are an important concern for vegetable processing, due its ability to induce browning after vegetables are cut. The HPP at 600 MPa for 5 or 30 min can be used to inactivate these enzymes in cocoyam and Peruvian carrot, guaranteeing the color and freshness of the tubers similar to the fresh cut vegetable.