Polyphenol content and antioxidative activity in apple purées with rhubarb juice supplement

The purpose of the present study was to evaluate the effect of rhubarb juice addition and peeling in apple purée production and storage on its phenolic composition, antioxidant activity and colour. The apple material used in this study was of two varieties: Sampion and Idared. The apple purées prepared in three variants (control purées, peeling purées and purées with 5% of rhubarb juice) were stored for 3 and 6 months at 30 °C. Apple purées were investigated for their antioxidant activity, change of colour and contents of phenolic compounds plus the polymer procyanidins and degree of polymerization (DP). The preparation of purées from apples without peeling and the addition of rhubarb juice during purée preparation had significant influence on polyphenol content. The purée prepared from peeled apples of Idared variety had phenolic content 2.2 times lower than the control sample (non‐peeled apples). The highest level of total polyphenols was found in Idared + rhubarb sample (129.82 mg 100 g^?1 purée). The content of this compound in Idared control sample was more than 2.8 times lower than in Idared purées with rhubarb. The use of non‐peeled Idared apples and 5% of rhubarb juice in purée preparation significantly increased polymeric procyanidins from 11.68 to 75.20 mg 100 g^?1 and other phenolics from 9.23 to 54.62 mg/100 g. This effect for Sampion apples was smaller. The procyanidins during purées storage were more stable in samples with rhubarb juice addition. The purée samples with the addition of rhubarb juice had higher antioxidant activity measured using ABTS (2,2′azinobis‐(3‐ethylbenzthiazoline‐6‐sulphonic acid)) than purée samples without the addition (two times higher for Idared variety) of rhubarb juice. After 3 and 6 months of storage at temperature 30 °C, the antioxidant capacity decreased in all purées. Rhubarb juice had only high and positive effect on L* value in the case of Idared variety. The results showed that all Sampion apple purées had higher L* values than Idared.     

Differentiation of intermediate products (concentrates and purées) from the fruit industry by means of phenolic content

Concentrates and purées are intermediate products in the manufacture of commercial fruit juices. In this paper, the phenolic content [total polyphenols (TP), ortho-diphenols (ORT) and catechins (CAT)] in a large number of concentrates and purées from apple and peach fruits has been determined. The relationships TP/ORT, TP/CAT and ORT/CAT have also been calculated. TP content was found to be significantly higher in the concentrates than in the respective purées whereas CAT content was significantly higher in the purée. ORT was found to be higher in purées than in apple concentrates, but the opposite was observed for peaches. The relationships TP/ORT, TP/CAT and ORT/CAT were higher for the concentrates than for the respective purées. In addition, values for ORT/CAT were higher for the peach products than for the respective apple products. The results show that these phenolic compound measurements enable differentiation between concentrates and purées, as well as between the fruit juices produced from them. The main advantage of measurements of total phenolic compounds is that they are easy to perform in a conventional laboratory, which makes them suitable for routine analysis.     

DRYING of COFFEE BERRIES IN A VIBRATED TRAY DRYER OPERATED WITH SOLIDS RECYCLE and SINGLE‐STAGE1

A vibrated tray dryer was tested for drying coffee berries. It consists of a vertical chamber (0.33 m × 0.18 m × 1.30 m) provided with four trays. the trays are supported by a vibrated shaft. Experimental tests were carried out at a vibration amplitude of 1 mm and at a variable frequency. the process itself consisted of feeding the vibrated tray dryer with an initial mass of coffee berries: after leaving the dryer through the discharge channel, the berries were fed again to the top of the dryer by a bucket elevator (intermittent operation with recycle of the coffee berries). Drying tests were carried out with drying air velocity of 2.4 m/s. the drying air control temperature was related with the temperature of the coffee berries at the discharge (under 45C). the drying time required for coffee berries to reach 12.6% (wb) moisture was 28 h, initial mass (moisture of 67% wb) was 5.54 kg. In this work the influence of vibration in single‐stage drying is also shown. the single‐stage operation shows that vibration (besides promoting the conveyance of coffee berries) also reduces the time of drying.     

Investigating the effect of food trays porosity on the drying process

Improving the dynamics of airflow behavior in the drying system is essential for improving its efficiency. In this study, the impact of the porosity of the plum-filled drying trays on the airflow behavior inside the chamber is investigated. Three configurations of constant porosity (30%, 50%, 70%), and 4 additional configurations of porosity varying linearly along trays 1 and 2 as a function of the x-axis are evaluated. To model the trays as a porous medium, the Power-low mathematical model was used, with the built-in parameters C₀ and C₁ were given experimentally. Both were formed as a subroutine in C++ and integrated into the CFD code, as was done for the integration of unsteady weather parameters. The CFD method used for visualizing and analyzing the airflow behavior in the drying chamber has been previously validated with the experimental result. The obtained results indicate that the average temperature of the drying trays reaches a maximum of 316,91 k at tray 1 for a porosity of 50% and an inlet velocity of 0.1 m/s. For the case of non-uniform trays porosity, it was found that for low air inlet velocity of 0.1 m/s, the velocity difference ΔV is generally low in cases (b) and (d), where it is equal respectively to 0.02 m/s and 0.01 m/s for tray 1, and 0.01 in both cases for tray 2. While for high air inlet velocity of 1 m/s the difference ΔV in both trays reaches 0.17 m/s.     

Electric properties of apple purée and pulpy apple juices

Results are presented of research, the aim of which has been to determine the selected physicochemical qualities, including electric quantities, of apple purées and pulpy juices obtained from them. The characteristics of the electric properties have covered the measurements of impedance (Z) and effective resistance (R), admittance (Y) and conductance (G), as well as equivalent parallel capacitance (Cp) and equivalent series capacitance (Cs). Changes have been determined in the purée properties relating to the technology of production as well as the function of diluting and the storage period. Apple purées, depending on the production technology, are characterized by the diversified, characteristic ranges of the resistivity and conductivity values. As the degree of the purée dilution rises, conductivity of juices falls. These relationships remain true throughout the purée storage period. In the conditions of the experiment, the measured values of resistivity and conductivity of pulpy juices clearly determine the content of apple purées in juices.     

Corrosion behaviour of tinplate cans in contact with tomato purée and protective (inhibiting) substances

The dissolution of iron and tin from tinplate cans filled with tomato purée (pH 4.34) and dioctyl sebacate oil (DOS), essential onion oil (EOO) or potassium nitrate was studied using atomic absorption spectroscopy (AAS), while nitrate was determined using high-performance liquid chromatography (HPLC). The maximum values found in cans were up to 284 mg kg^?1 for tin and 513 mg kg^?1 for iron at elevated storage temperature. Results indicated that the addition of EOO to tomato purée prevents the corrosion process in the case of tin, where concentrations were lowered from 223 to 28 mg kg^?1 for cans with DOS oil and EOO at 20°C, respectively (inhibition rate of 87%). On the other hand, the presence of EOO enhanced the corrosion process for iron increasing the concentration from 15 to 46 mg kg^?1 during 7 months of storage, although this value did not exceed maximum permitted value (50 mg kg^?1). In cans with tomato purée and potassium nitrate, dissolution of tin started after 30 (36°C) and 60 (20°C) days of storage as a consequence of nitrate action, which act as a corrosion accelerator. Since the addition of EOO improves the taste of canned tomato purée, its potential use as a corrosion inhibitor would be of interest.     

Thermal and High-Pressure Stability of Pectin-Converting Enzymes in Broccoli and Carrot Purée: Towards the Creation of Specific Endogenous Enzyme Populations Through Processing

The thermal and pressure stability of broccoli and carrot pectin-converting enzymes, in particular pectinmethylesterase (PME), β-galactosidase (β-Gal), and α-arabinofuranosidase (α-Af), were investigated in vegetable purée matrices. In situ enzyme inactivation by thermal and high-pressure processing (respectively 5 min at 25–80 °C at 0.1 MPa and 10 min at 0.1–800 MPa at 20 °C) was evaluated by measuring the residual enzyme activity in crude extracts of treated carrot, broccoli floret, and broccoli stem purée samples. PME was completely inactivated in all vegetable purée matrices after a 5-min treatment at 80 °C. After a treatment at 800 MPa (20 °C, 10 min) only 77–90 % of pressure stable PME was inactivated, depending on the matrix. β-Gal and α-Af enzymes were inactivated in the vegetable purée matrices by thermal treatments respectively at 67.5–72.5 and 80 °C. These enzymes showed some pressure resistance: treatments respectively at 600–700 and 600–750 MPa were necessary for one log-reduction of β-Gal and α-Af activity in the different purées at 20 °C. Under the assumption of a first-order inactivation model, inactivation rate constants and their temperature or pressure dependency were determined for the different enzymes. Based on differences in process stability of the enzymes in the individual purée matrices, the feasibility for the creation of specific endogenous enzyme populations by selective processing was evaluated.     

The applied pretreatment (blanching,ascorbic acid) at the manufacture process affects the quality of nectarine purée processed by hydrostatic high pressure

A nectarine purée was manufactured with different pretreatments (thermal blanching or ascorbic acid – AA – addition), and then, the purée was processed by high‐pressure treatment to evaluate the effect of the initial manufacture conditions in the stability of the processed purées. A thermal treatment was also carried out to compare the effect with the high‐pressure processing (HPP). All applied processes were effective to ensure the microbiological safety of the purées. However, the pretreatment (thermal blanching or AA addition) applied during the manufacture affected the final quality of the processed purées. Initially, the AA addition had a protective effect on colour degradation during the manufacture of the purées; however, when these purées were treated by HPP showed less colour stability during storage, lower bioactive compounds content, and antioxidant activity. In contrast, purées with an initial thermal blanching maintained better the quality after HPP and during storage.     

Rheological Characteristics of Pimento Purée: Theoretical Interpretation

Rheological characteristics of pimento purée were investigated at different temperatures (5 to 40 °C). The purée serum was a cloudy liquid (0to40 μm particles) with Newtonian behavior, and flow activation energy of 25.9 kJ/ mol. The power law model was applied to fit the pseudoplastic behavior of pimento purée. The activation energy for flow, evaluated with the Arrhenius‐Guzman equation, was low and depended on the variety. A modified Krieger‐Dougherty model with 2 parameters was proposed to describe the effect of wet pulp fraction on the relative viscosity. In the semi‐empirical model, the colloidal contribution to the viscosity at low shear rate and the parameter variations with the shear rate were considered.     

The effect of high pressure homogenization and endogenous pectin-related enzymes on tomato purée consistency and serum pectin structure

The influence of mechanical tissue disintegration techniques (i.e. blending and high pressure homogenization) and the stimulation of endogenous pectin-related enzymes (i.e. pectin methyl-esterase and polygalacturonase) on tomato purée consistency, serum composition and serum pectin structure were investigated. Serum pectin structure was characterized in terms of degree of methyl-esterification, acetylation, neutral sugar composition and molecular weight (M_w) distribution.Endogenous pectin methyl-esterase and polygalacturonase stimulation resulted in the lowest purée consistency and highest serum yield. However, when such purée was homogenized, a higher purée consistency and a low serum yield were observed. Moreover, the M_w of serum pectin was exceptionally high for the homogenized purées. The low methyl-esterified, linear and remarkably high M_w tomato serum pectin of the homogenized purées partly explains their increased consistency. This work demonstrated that high pressure homogenization can at least partially restore the consistency of tomato purée despite an initial consistency loss ascribed to enzymatic pectin degradation.Industrial relevanceThe synergistic action of endogenous pectin-related enzymes causes serum pectin de-polymerization that consequently results in consistency loss of tomato purée. Nevertheless, intense high pressure homogenization showed to influence serum pectin molecular weight and at least restore the consistency loss. This means that a high tomato purée consistency can still be achieved regardless of the initial action of endogenous enzymes in the tomato pieces or puréed tomato food system using high pressure homogenization. This offers an additional processing alternative in the production of tomato-based dispersions with a targeted functionality.     

The Effect of Endogenous Pectinases on the Consistency of Tomato–Carrot Purée Mixes

Tomato and carrot were subjected to a split-stream process designed to produce a tomato–carrot suspension with reduced consistency. Raw tomatoes, containing pectinmethylesterase and endo-polygalacturonase, were mixed with thermally pretreated (blanched versus cooked) carrots containing different levels of solubilized pectin. After mixing the vegetables, tomato pectinases were shown to act on both tomato and carrot pectin in case an incubation step at medium temperature level (30 min, 40 °C), to allow enzyme action, was performed. Carrot pectin, when present in a mix of tomato and blanched (5 min, 95 °C) carrot, was solubilized as well as depolymerized, whereas depolymerization of the thermo-solubilized carrot pectin by the tomato pectinases was observed in the tomato–carrot purée containing cooked (30 min, 95 °C) carrots. The final serum pectin properties were however similar for both purée types. Carrot contributed more to the consistency of the purée mix compared with tomato but by stimulating the action of the tomato pectinases at mild temperature (30 min, 40 °C), this contribution was lost which resulted in a consistency reduction of the purée mix. This purée liquefaction was larger for the tomato–carrot purée containing blanched instead of cooked carrots. Based on the results, it is suggested that the liquefying effect is related to solubilization and degradation of pectin that is counteracted by a reduction in particle size. The purée mix containing cooked carrot showed in this respect smaller particle sizes than the mix containing blanched carrot.     

Impact of enzymatic mash maceration and storage on anthocyanin and color retention of pasteurized strawberry purées

Strawberry purées were prepared using a commercial polygalacturonase (PG) and a highly purified pectinesterase (PE) preparation, respectively. To elucidate the effect of pectin on color stability following enzymatic pulp maceration, pectin composition was studied by isolating and fractionating the alcohol-insoluble residue from the strawberry purées. The purées were stored at +20 and +4 °C in the dark over a period of 24 weeks monitoring the amounts of monomeric and polymeric anthocyanins as well as antioxidant activities (FRAP, TEAC). Individual anthocyanins were analyzed by HPLC–DAD–MS ⁿ , and color measurements were obtained in the CIE L*a*b* system. Pectin composition was significantly modified following enzymatic maceration of the purées. While PG treatment generally resulted in pectin losses, oxalate-soluble pectins were increased in PE-treated purées. After 24 weeks of storage, the best anthocyanin retention was observed in PE-treated purées. Such products also revealed greatest anthocyanin half-life values and lowest proportion of polymeric pigments. Compared to an untreated control, enzymatic purée maceration using the PG was also beneficial for pigment retention, but less effective than PE. In contrast, color and antioxidant activity were independent of both enzymatic treatments. An initial heating step (90 °C, 10 s) for immediate inactivation of native enzymes such as polyphenoloxidases slightly improved pigment stability, while lowered temperature during mash maceration was less effective. However, by far best color and pigment retention were achieved when the purées were stored at 4 °C in the dark.     

MODELING and EXPERIMENTAL STUDY ON DRYING of APPLE SLICES IN A CONVECTIVE CYCLONE DRYER

The main objective pursued in this paper is to experimentally investigate the single layer drying behavior of apple slices in a convective type cyclone dryer and also to perform the mathematical modeling by using single layer drying models in literature. the experiments were conducted at drying air temperatures of 60, 70 and 80C in drying air velocities of 1 and 1.5 m/s. It was concluded that apple slices with the thickness of 12.5 mm would perfectly dry in the ranges of 280–540 mm while those with the thickness of 8 mm would dry in the ranges of 180–320 min in these drying conditions by using convective type cyclone dryer. Additionally, the mathematical model describing the single layer drying curves was determined by nonlinear regression analysis, and the logarithmic model was selected as the most suitable model to obtain the drying curve equation of apple slices. Considering the parameters such as drying time, drying rate, moisture transfer, velocity and drying air temperature it is suggested that the apple slices be dried at the above optimum processing conditions.     

Toxin production by strains of Aeromonas hydrophila grown in laboratory media and prawn purée

Toxin production by four strains of Aeromonas hydrophila grown at 30 and 37 degrees C in two laboratory media and prawn purée was studied. Three different cell lines were used to test for cytotoxic activity, haemolytic activity was tested against rabbit and guinea pig erythrocytes, proteolytic activity was assayed with azo-casein and enterotoxic activity using the suckling mouse assay. Results showed reduced cytotoxic and haemolytic activities in prawn purée compared with the two media, but in most cases increased proteolytic activity. No enterotoxic activity was observed in prawn purée although it was occasionally detectable in both laboratory media.     

Growth and germination of proteolytic Clostridium botulinum in vegetable-based media

The growth of proteolytic Clostridium botulinum from spore inocula and changes in spore counts in mushroom, broccoli, and potato purées were monitored. Four strains of proteolytic C. botulinum types A and B were inoculated separately at approximately 10(4) spores per ml in nutrient broth and vegetable purées incubated at 15, 20, and 30 degrees C for up to 52 days. The times for the cell populations to increase 1,000-fold (T1,000) in the tested vegetables (1 to 5 days at 30 degrees C, 3 to 16 days at 20 degrees C, 7 to > 52 days at 15 degrees C) were similar to those for meat or fish. Only temperature significantly influenced growth rate. In contrast, the lag phase depended on the strains and media tested, in addition to temperature. Lag times and T1,000S for proteolytic C. botulinum were longer for potato and broccoli purées than for mushroom purée. These differences were not related to different pHs or redox potentials. The germination level, evaluated as the decrease in the spore count, was low. The addition of a germinant mixture (L-cysteine, L-alanine, and sodium lactate) to some strains inoculated in vegetable purées resulted in an increase in germination, suggesting a lack of germination-triggering agents in the vegetable purées.     

Foam-mat drying of starfruit (Averrhoa carambola L.) purée. Stability and air drying characteristics

Foams were prepared from starfruit (Averrhoa carambola L.) purée by adding various concentrations of methocel. Overrun and density of the foams from various concentrations of methocel were compared. Relative stability of the foam was determined by comparing amounts of juice separated from foam at 70°C. Drying rates at two drying temperatures (70 and 90°C) were also compared. Quality of the dry and reconstituted powder was evaluated with simple sensory evaluation and Hunterlab instrument. Overrun and stability of foams increased with increasing methocel concentration until maximum value was obtained at a methocel concentration of 0.4% w/w. Falling rate was observed for foam dried at both temperatures. Drying time could be shortened by as much as 30 min when drying temperature was increased from 70 to 90°C. However, obvious colour and flavour changes were observed in the product dried at 90°C. This study has indicated that, under the experimental conditions employed, reasonably good powder characteristics can be obtained.     

Effect of high pressure processing on the quality of acidified Granny Smith apple purée product

The aim of the present study was the evaluation of the physicochemical, nutritional and microbial quality of acidified Granny Smith (GS) apple purée processed on industrial-scale high pressure system during 3 weeks of refrigerated storage (5 °C ± 1 °C). Two commercially feasible pressure treatments (400 and 600 MPa/5 min/20 °C) and a mild conventional pasteurization at 75 °C/10 min, with pasteurization values of P_70°C^7.5 = 8.15 min, were conducted and their effect on total vitamin C (total Vit C), ascorbic acid (AA) and total phenolic content (TPP), and on instrumental quality parameters (color, viscosity, soluble solids, titratable acidity and pH) were comparatively studied. Inactivation of indigenous microorganisms (total aerobic mesophilic and psychrotrophic counts and moulds and yeasts) of the apple product was also studied and monitored during storage. Total Vit C and AA contents were unaffected by the 400 MPa and the mild pasteurization treatment. TPP content was not changed during processing at 400 MPa, but was affected by the 600 MPa and also slightly by the pasteurization treatment. Experimental data on the loss of total Vit C during storage were described with a first-order reaction kinetic and times of half loss between 9.3 to 10.3 days could be estimated for the three studied processes. Storage provoked loss of TPP content and color deterioration of pressurized GS puree samples, which was attributed to enzymatic browning reactions. Microbial counts were reduced by the different preservation techniques below the detection limit (50 cfu g^?1) and storage revealed no further growth.Industrial relevanceThis is one of the first studies applying commercial industrial-scale high pressure equipment for the pasteurization of an acidified apple purée product. The pressures of 400 and 600 MPa with 5 min holding time at ambient temperature render economically feasible processes with high throughput and productivity. In the European Union the most important fruits in terms of production are apples. Apple purée is a largely consumed preserve in many households and beside apple juice or cider is one of the most important apple products in the market. In contrast to traditional apple purée preparation, high pressure processing or mild thermal treatments could imply new opportunities for the apple processing industry in developing more fresh-like, value-added apple products with reasonable shelf life.     

A Comparative Study of the Quality of Strawberry Purée Preserved by Continuous Microwave Heating and Conventional Thermal Pasteurization During Long-Term Cold Storage

This study was aimed at monitoring changes in the quality of strawberry purée preserved by continuous microwave heating (MV) at 90 and 120 °C for 10 s and conventional thermal pasteurization (CTP) at 90 °C for 15 min during cold storage (6 °C), and determining its shelf-life. The shelf-life of MV and CTP-preserved products established on the basis of microbiological changes was more than 52 weeks (<1 log cfu of yeasts, moulds, and total microbial count per gram). During this time, 43 and 34 % of polyphenols, 89 and 58 % of anthocyanins, as well as 57 and 52 % of antioxidant capacity decrease were noted, for MV and CTP-preserved samples respectively; vitamin C was completely degraded. Color changes were more visible for MV (ΔE?=?10.82) compared with the CTP-preserved sample (ΔE?=?5.14). The kinetic rate of degradation of nutrients was higher for MV- compared to CTP-preserved purée. The recommended cold shelf-life for the MV-preserved purée was estimated at 100 days, during which time it was of a superior quality compared with CTP-preserved purée.     

Aroma profile of a red plum purée processed by high hydrostatic pressure and analysed by SPME–GC/MS

The volatile profile of a plum purée processed by high pressure processing (HPP) was evaluated by the method of solid-phase micro-extraction gas chromatography/mass spectrometry (SPME–GC/MS). Two pressure intensity levels and three holding times were applied (400 and 600 MPa for 1, 150 and 300 s). Processed purées were compared to raw purée (unprocessed purée). A total of 40 volatile compounds were identified in the headspace of the plum purée. The major compounds identified were an aldehyde (hexanal) and two alcohols (hexan-1-ol and (Z)-hex-3-en-1-ol). Among the total compounds isolated (40), 23 compounds were significantly influenced by HPP. The modifications of these 23 volatiles represented changes of the 1.8% of the total aroma of the original purée. Results showed that the most intense treatments did not significantly alter the original aroma of plum purée. Therefore, HPP appears to be an alternative technology for the preservation of aromatic compounds of plum purée.Industrial relevanceHigh-pressure processing is one of the most successful technologies to obtain high-quality fruit purées. It is generally recognized that this treatment better preserves the original aroma of fruit. Two levels of pressure intensity and three holding times were applied (400 and 600 MPa for 1, 150 and 300 s) in order to know the effect of the treatments on the original aroma of plum. The combination of pressure and holding time did not affect the original aroma of plum. Results of this paper demonstrated that high-pressure processing preserves plum puree with a fresh-like aroma. On the other hand, a study of storage would be required to assess possible changes in the stability of the plum purée taking into account other parameters such as microbiological stability and inactivation of enzymes.