Impact of high‐pressure and traditional thermal processing of tomato purée on carotenoids,vitamin C and antioxidant activity

Bioactive compounds (carotenoids and vitamin C) and 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH^?) scavenging activity [50% depletion of initial DPPH^? radical (EC₅₀) and antiradical efficiency (AE)], in aqueous (AQ) and organic (OR) fractions, were measured in tomato purée subjected to high‐pressure (HP) (400 MPa/25 °C/15 min), low pasteurisation (LPT) (70 °C/30 s), high pasteurisation (HPT) (90 °C/1 min), freezing (F) (?38 °C/15 min), and HPT plus F (HPT + F). In addition, physical and physicochemical parameters were evaluated. CIELab uniform colour space parameters (lightness, L*; green‐red tonality, a*; and blue‐yellow tonality, b*) were significantly higher both in the untreated and in the HP tomato purée than in the rest of the samples. Individual and total carotenoids, and provitamin A carotenoids, were significantly higher in HP tomato purée than in the untreated and other treated tomato purées. Ascorbic acid and total vitamin C were significantly lower in HP, LPT, HPT, and HPT + F tomato purées than in the untreated and F purées. In the AQ fractions, we found an inverse significant correlation between both ascorbic acid and total vitamin C and EC_50AQ; and a positive significant correlation with AE_AQ. In the OR fractions, a significant correlation was found between EC_50OR and AE_OR parameters and lycopene and total carotenoids. Total scavenging activity (AQ + OR fractions) in HP tomato purée was similar to that in LPT, HPT, and HPT + F purées. Copyright © 2005 Society of Chemical Industry     

The Effects of Process-Induced Pectin Changes on the Viscosity of Carrot and Tomato Sera

The influence of process-induced pectin changes on the kinematic viscosity of the serum phases of carrot and tomato purées was investigated in this study. Variations in the amount of pectin present in the serum phase and pectin’s fine structure were induced by subjecting carrot and tomato to different thermal treatments, i.e. a mild and a strong heat treatment, followed by blending and high-pressure homogenisation at different pressure levels (0, 20 and 100 MPa). Changes in pectin structure were monitored by determination of the degree of methoxylation, analysing the molar mass distribution and immuno-dot blotting using anti-pectin antibodies. Characterisation of serum pectins revealed that a strong thermal treatment caused pectin thermosolubilisation and depolymerisation, especially in carrot sera, and high-pressure homogenisation provoked predominantly mechanical pectin solubilisation in carrot sera and pectin depolymerisation in tomato sera. It was observed that the kinematic viscosity of carrot sera was mainly affected by the amount of solubilised pectin, whereas in tomato sera, the kinematic viscosity could mainly be explained in terms of polysaccharide chain length. The degree of methoxylation of pectin, which has a broader distribution in tomato sera than in carrot sera, seemed to have a less pronounced role in determining the kinematic viscosity. In general, it could be concluded that serum viscosity is mainly determined by the amount and size of the solubilised pectin. The influence of serum viscosity on the rheology of the studied purées was limited as the rheology of this type of system is largely determined by the particle properties of the dispersed phase.     

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.     

Influence of fresh and processed fruit quality attributes on peach purée consistency index

Multivariate projection techniques were used to analyze the influence of several quality variables, measured both on fresh peach fruits and on peach purée, on Bostwick’s consistency index of the purée, which is the main parameter that the industry uses to take decisions regarding its commercialization. It was found that the variables measured on the fresh fruits were more useful to calibrate a prediction model of the consistency than the measures taken on the purée itself. The most important variable to predict consistency is the dry pulp-stone ratio, followed by the fruit firmness and the dry fruit weight, while the rest of variables have less influence in the modeling.     

Heat-Induced Changes in Free Amino Acids on Manufacturing Heated Pulps, Purées and Pastes from Tomatoes

The effect of heating on the free amino acid composition of processed tomato products, heated pulps, purées and pastes was examined. The major components of the fresh pulp were glutamic acid, γ-aminobutyric acid, aspartic acid, glutamine and asparagine. The heating process caused about a 40% loss of the total amino acids, which was attributable mostly to decreases in glutamic acid, glutamine and aspartic acid. Neither aromatic amino acids nor basic amino acids decreased in this process. Additional low temperature heating applied to the heated pulp to manufacture purées and pastes caused less effects than the high temperature heating used to prepare the pulp.     

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.     

Baby food production chain: pesticide residues in fresh apples and products.

During 3 years of a monitoring programme, 522 samples of fresh apples, six brands of fruit purées and various types of fruit baby food prepared from these materials were analysed. Each sample was examined for the presence of 86 GC amenable pesticide residues. The reporting limits of the procedure employed for sample analyses were in the range 0.003-0.01 mg kg(-1). Pesticide residues were detected in 59.5% of the samples of fresh apples. However, maximum residue levels (European Union MRLs) were exceeded only in 1.4% of samples. The levels of residues in 'positive' fruit purées were substantially lower, overall with residues detected in 33% of samples. Fruit baby food represented the commodity with the lowest incidence of residues being detected in only 16% of samples. The 0.01 mg kg(-1) MRL was exceeded in 9% of these products. Multiple residues were found in 25% of fresh apples and in 10% of fruit purées. None of fruit baby food samples contained more than a single residue. Organophosphorus insecticides and fungicides representing phtalimides, sulphamides and dicarboximides were the most frequently found residues. To obtain more knowledge on the fate of residues during fruit baby food production, processing experiments employing apples with incurred residues (fenitrothion, phosalone and tolylfluanid) were conducted. Washing of apples did not significantly reduce the content of pesticides. Steam boiling followed by removal of peels/stems was identified as the most efficient steps in terms of residues decrease (phosalone) or complete elimination (fenitrothion and tolylfluanid).     

Analysis of sensory and physicochemical data on commercial tomato purée with pattern recognition techniques

The correlations between analytical parameters and some typical sensory attributes of commercial tomato purée (8–14 °Brix) were studied. In order to ensure the widest possible variance multivariate analyses was used. A model was obtained that could describe the different contribution of the analytical variables to the sensory attributes examined. Cluster analysis revealed the existence of two distinct sub-groups; traditional by tomato purée and organically produced tomato purée.     

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.     

Antimicrobial Activity of Binary and Ternary Mixtures of Vanillin,Citral, and Potassium Sorbate in Laboratory Media and Fruit Purées

The susceptibility of Escherichia coli, Salmonella enteritidis, Saccharomyces cerevisiae, and Zygosaccharomyces bailii to binary and ternary mixtures of potassium sorbate (KS), vanillin (V), and citral (C) was evaluated according to the Berenbaum experimental design, in laboratory media. For some V/C combinations, KS inhibitory concentrations were determined in agarized melon and mango purées by the spiral gradient endpoint (SGE) method. In laboratory media, inhibitory antimicrobial combinations were generally additives. For the yeasts, some synergistic effects were observed. All Berenbaum mixtures which resulted inhibitory in laboratory media were confirmed in the fruit purées. When the SGE method was used, several inhibitory ternary mixtures were found. The lowest inhibitory KS concentrations, estimated for a given V/C combination, corresponded to the bacteria assayed in melon purée. Z. bailii was not inhibited at any condition. Some synergistic antimicrobial combinations (595 ppm V + 251 ppm C + 8 ppm KS in melon and 280 ppm V + 123 ppm C + 8 ppm KS in mango purées) could be useful to achieve a desired inhibitory effect in fruit purées while reducing their concentrations.     

Changes after high-pressure processing on physicochemical parameters,bioactive compounds,and polyphenol oxidase activity of red flesh and peel plum purée

Physicochemical parameters (instrumental color, soluble solid content, titratable acidity, and pH), bioactive compounds (total phenols and anthocyanins), total antioxidant activity, and enzymatic activity of polyphenol oxidase (PPO) were evaluated after the application of hydrostatic high-pressure (HP) treatment on a plum purée (cv. Crimson Globe, with red flesh and peel). Different pressure levels (400, 500, and 600 MPa) were applied at different processing times (1, 150, and 300 s). HP-treated purées were compared with the untreated purée. The inactivation of indigenous microorganisms (total aerobic mesophilic and psychrotrophic counts, and molds and yeasts) of the plum purée after all high-pressure treatments was sufficient to reduce spoilage microorganisms present in plum purée to undetected levels in most of HP-treated purées. No significant changes were observed in pH and soluble solid content after processing. The combined treatments (pressure level and processing time) did not reach a sufficient inhibition of PPO enzyme. Processing induced a significant increase in L*, a*, hue, and chroma, which could enhance the redness perception of treated purées. All HP-treated purées showed a slight reduction in anthocyanins and antioxidant activity after processing. Nevertheless, total phenols were not significantly affected by HP-treatments. In conclusion, high-pressure processing keep most quality parameters and nutritional compounds levels, although, it did not achieve the inhibition of browning related enzymes, which could reduce the shelf-life of plum products during storage.Industrial relevanceHigh-pressure processing is one of the most successful technologies to obtain high-quality fruit purées. However, the application of this technology to certain products presents some difficulties due to high-pressure and usually does not affect the activity of browning related enzymes. The present study evaluates the effect of high-pressure treatments on the color, bioactive compounds, and polyphenol oxidase enzyme of plum purée. This is one of the first studies about the application of high pressure technology for the preservation of red flesh and peel plum. High-pressure treatments did not achieve the total inactivation of the polyphenol oxidase enzyme, however, total phenols and anthocyanins were well preserved after the treatments. Our results also show that redness and color luminosity of plum HP-treated purées were well retained. Therefore, high pressure processing offers the opportunity to processing plum purée with fresh-like properties. Nevertheless, the storage of the product could be limited due to the lack of effect of the pressure on the enzyme activity.     

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.     

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.     

Reduction of Furan Formation by High-Pressure High-Temperature Treatment of Individual Vegetable Purées

The present study addressed the need for furan mitigation measures at the level of food production, where the effects of extrinsic (process-related) and intrinsic (product-related) properties on furan formation in vegetable-based systems were investigated. For the first time in the literature, the effect of high-pressure high-temperature (HPHT) processing on the formation of furan was demonstrated. HPHT processing was proven to be an interesting alternative for furan reduction in vegetable-based systems, when aiming for sterilization intensities. Following HPHT treatment, the furan concentrations of a wide range of individual vegetable purées dropped to levels close to the analytical limits (1–2 ng/g purée). A higher processing cost might limit the use of HPHT processing to high-value added products, which means that for many other conduction-heated food products, conventional heating would remain the standard technology. As a first step towards control of furan formation in the latter products, a mixed model regression was used to identify the major precursors in vegetable-based systems. Significant correlations were observed for vitamin C and sugars, which were attributed to the efficiency of the conversion and high concentrations, respectively. Next to furan, the HPHT- and thermally treated purées were analyzed for 2- and 3-methylfuran, which are likely to undergo the same metabolic fate as furan. For most of the vegetables tested, the total amount of methylfuran found in the thermally treated purées could not be ignored. Similarly to furan, there was a clear reduction in the concentrations found in the HPHT-treated purées.     

Changes in flavour composition during thermal concentration of apricot purée

Qualitative and quantitative changes in the flavour composition of Italian apricots (Prunus armeniaca, L.) during thermal concentration of a fruit purée have been investigated by gas chromatographic (GC) and GC-mass spectrometric techniques. The results demonstrate that the enantiomeric distribution of γ-lactones in apricot is not affected by thermal processing. A significant increase in the content of partly racemic mono- and dihydroxylated terpenic alcohols during processing has to be attributed to glycosidically bound precursors. The quantitative distribution of flavour compounds in fresh apricots, fruit purée, fruit and flavour concentrate is discussed.     

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.     

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.     

Impact of high pressure processing on total antioxidant activity,phenolic, ascorbic acid,anthocyanin content and colour of strawberry and blackberry purées

The present study was undertaken to assess the effect of high pressure treatments and conventional thermal processing on antioxidant activity, levels of key antioxidant groups (polyphenols, ascorbic acid and anthocyanins) and the colour of strawberry and blackberry purées. Bioactive compounds (cyanidin-3-glycoside, pelargonidin-3-glucoside, ascorbic acid) and antioxidant activity were measured in strawberry and blackberry purées subjected to high pressure treatment (400, 500, 600 MPa/15 min/10–30 °C) and thermal treatments (70 °C/2 min). Samples were assessed immediately after processing. Different pressure treatments did not cause any significant change in ascorbic acid (p > 0.05). In contrast, following thermal processing (P₇₀ ≥ 2 min) ascorbic acid degradation was 21% (p < 0.05) as compared to unprocessed purée. However, no significant changes in anthocyanins were observed between pressure treated and unprocessed purées (p > 0.05), whereas conventional thermal treatments significantly reduced the levels (p < 0.05). In general, antioxidant activities of pressure treated strawberry and blackberry purées were significantly higher (p < 0.05) than in thermally processed samples. Colour changes were minor (ΔE) for pressurised purées but the differences were slightly higher for thermally treated samples. Redness of purées was well retained in high pressure treated samples. Therefore processing strawberry and blackberry by high pressure processing could be an efficient method to preserve these products quality. Hence high pressure processing (HPP) at moderate temperatures may be appropriate to produce nutritious and fresh like purées.Industrial relevanceThis research paper provides scientific evidence of the potential benefits of high pressure processing in comparison to thermal treatments in retaining important bioactive compounds. Antioxidant activity (ARP), ascorbic acid, and anthocyanins after exposure to high pressure treatments (400–600 MPa) were well retained. Our results also show that redness and colour intensity of strawberry and blackberry purées were better preserved by high pressure processing than conventional thermal treatment. From a nutritional perspective, high pressure processing is an attractive food preservation technology and offers opportunities for horticultural and food processing industries to meet the growing demand from consumers for healthier food products. Therefore high pressure processed foods could be sold at a premium than their thermally processed counterparts as they will have retained their fresh-like properties.