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.     

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

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

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.     

Carotenoids and lipophilic antioxidant capacities of tomato purées as affected by high hydrostatic pressure processing

The effect of high hydrostatic pressure (HHP) (450–550–650 MPa/5–10–15 min) on the carotenoid profile of purées obtained from commercial tomato varieties (Maliniak, Cerise, Black Prince and Lima) was investigated. The carotenoids profile was analysed using high performance liquid chromatography (HPLC-DAD). Photochemiluminescence (PCL_ACL), ferric-reducing antioxidant power (FRAP) and cyclic voltammetry (CV) assays were used to determine the antioxidant capacity of the lipophilic extracts. The results demonstrated that at certain processing conditions, HHP distinctly enhanced antioxidant capacity of the studied material. A significant reduction in lycopene and β-Carotene concentration was observed for all the HHP-treated purées. In contrast, lutein found in the purée extracts of Cerise and Black Prince tomatoes was slightly affected at 550 MPa/5 min and 650 MPa/5 min. Among all the carotenoids studied, lutein strongly and significantly affected PCL_ACL and CV parameters. In contrast, lycopene had a negligible effect on the examined parameters.     

The Evaluation of Antioxidant Interactions among 4 Common Vegetables using Isobolographic Analysis

Isobolographic analysis was used to assess the antioxidant interactions (synergism, addition, and antagonism) of 4 common vegetables (tomato [T], carrot [C], eggplant [E], and purple potato [P]). The lipophilic (L) extracts of T and C (main carotenoids), the hydrophilic (H) extracts of E and P (main phenolics) were mixed by the certain ratios (1:9, 3:7, 1:1, 7:3, 9:1, w/w) and their antioxidant activities were investigated by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and 2,2’‐Azinobis‐(3‐ethylbenzthiazoline‐6‐sulphonate) (ABTS) radical scavenging assays, respectively. Most of the binary mixtures (LC‐HE, LC‐HP, HE‐HP, LT‐HE, and LT‐HP combinations) showed the synergistic antioxidant effects. In DPPH assay, the greatest antioxidant activity of vegetable combinations was 1:9 LT‐HP (EC₅₀: 2.45 ± 0.13 mg/mL), followed by 9:1 HE‐HP (EC₅₀: 3.62 ± 0.12 mg/mL) and 1:9 LC‐HE (EC₅₀: 3.74 ± 0.47 mg/mL). In ABTS assay, the greatest antioxidant activity of vegetable combinations was 9:1 HE‐HP (EC₅₀: 4.20 ± 0.10 mg/mL), followed by 7:3 HE‐HP (EC₅₀: 4.41 ± 0.63 mg/mL) and 1:1 HE‐HP (EC₅₀: 5.35 ± 0.85 mg/mL). Among these combinations, 1:1 LC‐HE combination showed the highest synergistic antioxidant effects in DPPH assay (synergistic rate: 87.4%), and 7:3 LC‐HE combination showed the highest synergistic antioxidant effects in ABTS assay (synergistic rate: 87.0%). The mixtures of phenolics and carotenoids with suitable ratios in vegetables effectively enhanced the synergistic antioxidant effects.     

Screening of tomato purée for excessive mould content by near infrared spectroscopy: A preliminary evaluation

Preliminary experiments demonstrated that near infrared spectroscopy (n. i. r.s.) could be used to measure the amount of mould (Botrytis cinerea or Alternaria tenuissima) added to fresh tomato homogenate. In subsequent work, fresh tomatoes that had been allowed to become mouldy were used to prepare a series of tomato purées containing known quantities of mouldy fruit. N.i.r.s. of the freeze-dried purée was again successful in estimating the amount of contamination as per cent mouldy fruit. Regression analysis selected wavelengths which could be associated with absorption bands of chitin, the major carbohydrate in the cell walls of moulds. It may therefore be possible to utilise n.i.r.s. as a screen for mould in tomato purées if the present success with B. cinerea and A. tenuissima can be extended to the complete range of moulds encountered in tomato products.     

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.     

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.     

Effect of oxygen availability and pH on the furan concentration formed during thermal preservation of plant-based foods

Thermally treated fruit- and vegetable-based foods are important contributors to the furan exposure of children and adults. Furan reduction by adding or removing precursors from the product has proven to be challenging because of major food constituents and interactions involved in the reaction pathways leading to furan formation. Instead of intervening at the precursor level, it might be more feasible to influence these formation pathways by adjusting the matrix properties of the product. As opposed to many previous literature sources, the present study investigated the effects of oxygen availability (normal versus reduced) and pH (acid versus low acid) on the furan formation in a real food system. Different combinations of both matrix properties were prepared in a reconstituted potato purée and subjected to a thermal treatment with a pasteurisation or sterilisation intensity. Irrespective of the addition of the furan precursors ascorbic acid, fructose and fatty acids, a considerable furan reduction was observed for the sterilised purées (F₁₂₁¹⁰ = 15 min) with either a reduced oxygen availability (0.1–1.8 mg l^–1) or at pH 3. The effects of both matrix properties were less pronounced in the pasteurised purées (P₉₀¹⁰ = 10 min), because of the lower furan concentrations. Even though the mechanisms of furan reduction for both types of matrix properties could not be fully elucidated, the results showed that lowering the oxygen concentration or pH prior to thermal processing offers a powerful, additional strategy for furan mitigation in thermally treated plant-based foods.     

Effect of thermal and high pressure processing on antioxidant activity and instrumental colour of tomato and carrot purées

Total antioxidant activity, levels of bio-active compound groups and instrumental colour of tomato and carrot purée subjected to high pressure treatment (400–600 MPa/15 min/20 °C) and thermal treatments (70 °C/2 min) were measured. Antioxidant activity in tomato and carrot purée was significantly higher (p < 0.05) than in untreated or thermally processed samples. High pressure treatments at 600 MPa retained more than 90% of ascorbic acid as compared to thermal processing in tomato purées. Heat treatments caused a rapid decrease in ascorbic acid (p < 0.05). Phenolic contents were in general un-affected by thermal or high pressure treatments. Colour parameters were significantly affected (p < 0.05) by thermal and high pressure processing. Principal component analysis (PCA) revealed that the first two components represented 97% and 92% of the total variability in instrumental colour parameters with respect to processing for tomatoes and carrots respectively.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 carotenoids after exposure to high pressure treatments (400–600 MPa) were well retained. Our results also show that redness and colour intensity of purées were better preserved by high pressure processing than conventional thermal treatment. It would appear from a nutritional prospective, high pressure processing is an excellent food processing technology which has the potential to retain compounds with health properties in foods. Therefore high pressure processed foods could be sold at a premium over their thermally processed counterparts as they will have retained their fresh-like properties.     

Use of banana purée from three indigenous Thai cultivars as food matrices for probiotics and application in bio‐set‐type yoghurt production

This research studied the use of banana purée from three indigenous Thai cultivars (Kluai Hom Thong, Kluai Namwa and Kluai Khai) as probiotic carrying agents in food and application in bio‐set‐type yoghurt. Kluai Khai purée had promising indication of prebiotic activity on Lactobacillus paracasei Lpc‐37 with the highest probiotic activity score. When Lpc‐37 cell was incorporated into Kluai Khai purée, its cell counts increased by 0.8 log CFU g^?1 and it adhered to purée, as seen by the proliferating cells. Therefore, Kluai Khai purée mixed with Lpc‐37 was selected for the production of bio‐set‐type yoghurt. The results showed that viable cells increased more than 0.8 log CFU g^?1 during storage. This study reflected the achievement of using Kluai Khai purée as food matrix for carrying ‘active probiotic cells’ in bio‐yoghurt production. This methodologically developed prototype could be an interesting alternative for value adding of indigenous fruits.     

Effect of refrigerated storage on vitamin C and antioxidant activity of orange juice processed by high-pressure or pulsed electric fields with regard to low pasteurization

A better knowledge of the effect of refrigerated storage on the nutritional and antioxidant characteristics of foods processed by emerging technologies with regard to thermal traditional technology is necessary. Thus, freshly squeezed orange juice was processed by high-pressure (HP) (400 MPa/40 °C/1 min), pulsed electric fields (PEF) (35 kV/cm/750 μs) and low pasteurization (LPT) (70 °C/30 s). The stability of vitamin C and antioxidant activity was studied just after treatment and during 40 days of refrigerated storage at 4 °C. The determination of total vitamin C (ascorbic acid plus dehydroascorbic acid) was achieved by HPLC whereas the antioxidant activity was assessed by the measurement of the DPPH• radical scavenging. Just after treatment, all treated orange juices showed a decrease lower than 8% in vitamin C content compared with the untreated one. At the end of refrigerated storage, HP and LPT juices showed similar vitamin C losses (14 and 18%, respectively) in relation to untreated juice, although HP juices maintained better the vitamin C content during more days than LPT juices. Regarding antioxidant activity, after 40 days at 4 °C, differences among treated juices were no significant in terms of antiradical efficiency (AE=1/EC₅₀T_EC50). HP and PEF may be technologies as effective as LPT to retain antioxidant characteristics of orange juice during refrigerated storage.     

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.     

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.     

Characterising polysaccharides in cherimoya (Annona cherimola Mill.) purée and their enzymatic liquefaction

Polysaccharides isolated in the alcohol-insoluble residues (AIR) from cherimoya (Annona cherimola Mill.) were characterised for contents of soluble pectin, cellulose, hemicellulose and lignin, and the distribution of neutral sugars and uronides in water-soluble pectin (WSP) and water-insoluble AIR (WAIR) fractions. For WSP, the predominant neutral sugar was arabinose and, for WAIR, cellulosic glucose and xylose. Two enzyme preparations were tested for their capacity to release neutral sugars and uronides from WAIR. The optimal incubation temperature (45 °C) and the most effective preparation—rich in pectinase, cellulase and xylanase activities—were selected according to a central composite rotatable design (CCRD). Enzyme was also applied to native cherimoya purée according to another CCRD, varying the enzyme concentration and incubation time. Native purée exhibited strong shear-thinning behaviour with high, extrapolated, yield stress. During enzymatic treatment, behaviour was less shear thinning, and yield stress, consistency index and Bostwick consistency tended to decrease, giving rise to purées of different rheological properties.     

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.     

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.     

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.