Enzymatic Firming of Processed Red Pepper by Means of Exogenous Pectinesterase

Abstract

The objective of this investigation was to demonstrate that the firmness of a commercial vegetable product, diced and frozen red pepper (Capsicum annum var. Sendt), could be improved by the use of exogenous pectinesterase in an industrially relevant process. The diced pepper pieces 10?×?10?×?7?mm³ were infused under vacuum with a commercially available pectinesterase. The range of optimal process conditions was: 15–20°C, 45?min infusion time, a 10–25?mM CaCl₂ infusion brine, a w/w ratio of pepper fruit to infusion brine of 1.5:1, and an enzyme dosage of 30–60 pectinesterase units (PEU) per kg pepper fruit. The firmness as measured by back extrusion was improved by a factor of two to three. The effect of firming was robust and conserved after freezing and heating in a simulated household cooking process. The firming process seems easily adaptable to industrial conditions and may be applicable to other vegetable and fruit products.     

Innovative Methods for Removal of PCR Inhibitors for Quantitative Detection of Plesiomonas shigelloides in Oysters by Real-Time PCR

A quantitative assay for Plesiomonas shigelloides in pure culture and oysters based on the real-time polymerase chain reaction (Rti-PCR) was developed. The methodology involved the treatment of oyster tissue homogenates with formaldehyde, differential centrifugation, and treatment of samples with activated charcoal coated with Pseudomonas fluorescens. With seeded oyster tissue homogenates, without formaldehyde or coated charcoal treatments, the lowest level of detection for P. shigelloides was 1 × 10⁷ genomic targets per gram of tissue, equivalent to 2.5 × 10⁵ genomic targets per Rti-PCR. The addition of 4% formaldehyde to tissue homogenates reduced the minimum level of detection of P. shigelloides to 1 × 10⁵ genomic targets per gram of tissue, equivalent to 2.5 × 10³ genomic targets per real-time PCR. The treatment of tissue homogenates with only activated charcoal coated with P. fluorescens reduced the minimum level of detection of P. shigelloides to 1 × 10⁴ genomic targets per gram, equivalent to 2.5 × 10² genomic targets per real-time PCR, without DNA purification or enrichment. The combination of adding 4.0% formaldehyde to oyster tissue homogenates and treating with coated charcoal reduced the level of detection of P. shigelloides to 1 × 10³ genomic targets per gram, equivalent to 25 genomic targets per real-time PCR. The linear range of detection was from 1 × 10³ to 1 × 10⁶ genomic targets per gram without enrichment.     

EFFECTS OF RAW MATERIALS AND PROCESS VARIABLES ON THE HEAT PENETRATION TIMES, FIRMNESS, AND PECTIC ENZYME ACTIVITY OF DICED TOMATOES (HALLEY BOS 3155 CV)

The effects of raw materials and process variables on the heat penetration times into diced tomatoes (Halley Bos 3155 cv) were evaluated. Variables included dice size (1.27 and 2.54 cm), maturity at harvest (red and red+2 weeks), and processing temperature (88 and 92C). Heat penetration times between dice sizes were significantly different, but not between maturities or processing temperatures. Tomatoes were also evaluated for firmness, pectin-methylesterase (PME) and polygalacturonase (PG) activities. Half-inch size diced tomatoes were processed at 88 and 92C, and evaluated for firmness using the shear-compression method. Firmness decreased to 60% of the initial raw firmness from 8.8 × 10⁵ to 5.3 × 10⁵ g-mm after 15 s at 88C, and to 50% from 8.8 × 10⁵ to 4.4 × 10⁵ g-mm after 15 s at 92C. Diced tomato firmness showed a slight firming trend after 150 s at both temperatures. PME was inactivated after 45 s, while 5% residual PG activity remained after 3 min.     

Sorption of aroma compounds in PET and PVC during the storage of a strawberry syrup

The sorption of 14 aroma compounds into PET and PVC was monitored during storage of a strawberry syrup for 1 year. Concentrations in the syrup and in the polymer were determined during storage and compared with previously published results obtained with glass bottles. Apparent partition coefficients between the polymer and the syrup (noted K_app) were estimated from experimental kinetics without reaching equilibrium K_app values and optimally identified from the kinetic data obtained between 30 and 90 days. They exhibited a similar behaviour for both polymers with values were between 2 × 10^-5 and 2 × 10^-3, 4 × 10^-5 and 3 × 10^-2, respectively, for PET and PVC. The variation of K_app values in PET was mainly correlated to the polarity of tested compounds as assessed by their log P values. By contrast, the variations in K_app values for PVC were mainly related to their chain lengths. Due to slightly higher partition coefficients and diffusion coefficients in PVC compared with PET, the amount of absorbed aroma was four times higher in PVC than in PET; however, the amount of absorbed aroma compounds was less than 0.1% of the initial amount present into the syrup, except for octyl butanoate. The variation in concentration in the syrup was interpreted as a combination of a degradation process and a transport process into the packaging material. Both effects were particularly noticeable for both PET and unstable aroma compounds.     

Migration of a UV stabilizer from polyethylene terephthalate (PET) into food simulants

The migration characteristics of the UV stabilizer Tinuvin 234 (2-(2H-benzotriazol-2-yl)-4,6-bis (1-methyl-1-phenylethyl)phenol) into food simulants has been measured from polyethylene terephthalate (PET) using HPLC with UV detection. Ethanol/water, isooctane and a fractionated coconut oil simulant (Miglyol®) were used as food simulating solvents. The migration characteristics were measured at temperatures in the range of 40-70°C. Diffusion coefficients were determined to be in the range of 1 × 10^-14 cm² s^-1 to 1 × 10^-18 cm² s^-1. At 40°C, the amount of migration into 95% ethanol after 10 days was 2 μg dm^-2. Isooctane is determined to be a good fatty food simulant that provides similar results for PET to those of fatty foods.     

Aflatoxin and ochratoxin A content of spices in Hungary

In October and November 2004, 91 spice samples (70 ground red pepper, six black pepper, five white pepper, five spice mix and five chilli samples), the majority of which originated from commercial outlets, were analysed for aflatoxins B₁, B₂, G₁ and G₂ (AFB1, AFB2, AFG1, AFG2) and ochratoxin A (OTA) content by high-performance liquid chromatography (HPLC) after immunoaffinity column clean-up. Eighteen of the 70 ground red pepper samples contained AFB1, seven of them in a concentration exceeding the 'maximum level' of 5 µg kg^-1 (range 6.1-15.7 µg kg^-1). Of the other spices assayed, the AFB1 contamination of one chilli sample exceeded 5 µg kg^-1 (8.1 µg kg^-1). Thirty-two of the 70 ground red pepper samples contained OTA, eight of them in a concentration exceeding the 10 µg kg^-1 'maximum level' (range 10.6-66.2 µg kg^-1). One chilli sample was contaminated with OTA at 2.1 µg kg^-1. The AFB1 and OTA contamination of ground red pepper exceeding the 'maximum level' (5 and 10 µg kg^-1, respectively) was obviously the consequence of mixing imported ground red pepper batches heavily contaminated with AFB1 and OTA with red pepper produced in Hungary. This case calls attention to the importance of consistently screening imported batches of ground red pepper for aflatoxin and ochratoxin A content and strictly prohibiting the use of batches containing mycotoxin concentrations exceeding the maximum permitted level.     

Clostridium perfringens and its toxins in minced meat from Kars, Turkey

The aim of this study was to determine the prevalence of Clostridium perfringens and its toxins in minced meat. A total of 96 minced meat samples were collected from local markets (16) and small butcher's shops (80) in Kars (Turkey). Samples were analysed for the presence of C. perfringens and its toxins using a commercially available ELISA kit. A total of 31 (32%) Clostridium spp. strains were isolated and 17 (55%) of these isolates were identified as C. perfringens. Four (25%) of the samples from local markets and 27 (34%) from small butcher's shops were contaminated with Clostridium spp. Furthermore, C. perfringens was isolated from two (12%) and 15 (19%) samples from local markets and small butcher's shops, respectively. Mean counts of Clostridium spp. were 2.2 ± 0.83 × 10² CFU g^-1 for local markets and 4.35 ± 8.53 × 10² CFU g^-1 for small butcher's shops; mean counts for C. porringers were 2.75 ± 0.21 × 10² and 6.82 ± 10.96 × 10² CFU g^-1 from markets and butcher's shops, respectively. The number of samples contaminated with both Clostridium spp. and C. perfringens was higher in small butcher's shops than in local markets. Moreover, higher numbers of Clostridium spp. and C. perfringens were isolated in samples from small butcher's shops than from local markets. A total of 13 (13%) samples were also positive for toxins produced by the organism, as detected by ELISA. Eleven samples from small butcher's shops and two samples from local markets were positive for the C. perfringens toxins tested. Moreover, two (12%), one (1%), four (4%) and two (2%) samples were contaminated with C. perfringens types A, B, C and D, respectively. In conclusion, some meat samples collected from local markets and small butcher's shops contained C. perfringens and its toxins and, therefore, present a potential risk of food poisoning.     

Survey of formaldehyde, acetaldehyde and oligomers in polyethylene terephthalate food-packaging materials

Polyethylene terephthalate (PET) is frequently used as a packaging material for beverage bottles, fruit and vegetable trays, and egg crates in Japan. Levels of formaldehyde (FA), acetaldehyde (AA) and PET oligomers in various PET food packaging were determined. PET samples were initially dissolved in trifluoroacetic acid with 2,4-dinitrophenylhydrazine to derivatize formaldehyde and acetaldehyde to their dinitrophenylhydrazones. The stable derivatives along with the oligomers were analysed using HPLC with ultraviolet light detection at 360 and 254 nm, respectively. The PET pellets contained 3.5-12.4 µg g^-1 AA and 4.0-7.2 mg g^-1 oligomers, while FA was below the determination limit. FA, AA and oligomer levels in Japanese bottles were 0.6-3.0 µg g^-1, 8.4-25.7 µg g^-1 and 5.0-8.7 mg g^-1, ND-1.6 µg g^-1, 5.0-13.1 µg g^-1 and 4.9-8.2 mg g^-1 in French and Italian bottles, and ND-1.2 µg g^-1, 9.1-18.7 µg g^-1 and 5.6-8.0 mg g^-1 in US and Canadian bottles, respectively. Compared with European bottles, Japanese bottles contain higher FA and AA levels. In sheet-moulding products, their contents were determined as ND-1.1 µg g^-1, 11.5-43.1 µg g^-1 and 4.6-9.2 mg g^-1, respectively. The results show that sheet-moulding products contain lower FA and higher AA in comparison with bottles. FA and AA are considered to be generated from PET during the heating process for moulding the pellets to bottles or sheet-moulding articles and de-aeration during the sheet-moulding process is effective in removing FA. In contrast, the level of the oligomers remains unchanged during the moulding process from pellets to bottles or sheet products.     

Firmness and Cell Wall Characteristics of Pasteurized Jalapeño Pepper Rings as Affected by Preheating and Storage

Changes in cell wall pectic substances, degree of pectin methylation, bound calcium and firmness were determined in preheated and nonpreheated fresh pack jalapeño pepper rings stored for 5 mo. Pepper rings preheated for 60 min at 50°C in a brine solution (8% NaCl and 0.2% CaCl₂, were firmer, had more nonextrctable pectins (NXP), more bound calcium, less water-soluble and chelator-soluble pectins (CSP), and less pectin methylation than nonpreheated pepper rings. The greater formation and maintenance of nonextractable pectins, which resisted acid hydrolysis during pasteurization and storage is probably an important factor in firming.     

Flow-through spectrophotometric sensor for the determination of saccharin in low-calorie products

A simple, rapid and inexpensive monoparameter flow-through sensor has been developed for the determination of saccharin in low calorie and dietary products. The method is based on the transient adsorption of the sweetener on Sephadex G-25 solid phase packed to a height of 20 mm in the flow cell. The optimal transient retention of the synthetic sweetener, in terms of sensitivity and sampling frequency, was obtained when pH 2.75 citric acid-sodium citrate buffer 5 × 10^-3 M was used as a carrier at a flow-rate of 1.5 ml min^-1. Saccharin was determined measuring its intrinsic absorbance at 217 nm at its residence time. Calibration graphs for peak height and peak area were linear over the range 5.0-200.0 μg ml^-1, RSD 1.18%, and 1.0-200.0 μg ml^-1, RSD 0.78%, respectively. Saccharin was determined in several food samples measuring height or area peak, obtaining recoveries ranging between 98-104 and 99-102% for height and area peak, respectively. The procedure was validated for use in the determination of saccharin in low calorie and dietary products giving reproducible and accurate results.     

Improved Firmness in Calcified Diced Tomatoes by Temperature Activation of Pectin Methylesterase

ABSTRACT: The effects of temperature and calcium on pectin methylesterase (PME) activity and texture in tomato pericarp material were examined. Heating thin slices of pericarp to temperatures between 50°C and 75°C led to the rapid evolution of methanol from the material, indicating an activation of PME. This activity was further stimulated when CaCl₂ (up to 2.0% w/v) was added. When applied to half-inch diced tomato pericarp, the same conditions that led to the activation of PME also improved firmness. Diced tomatoes treated for 5 min with 0.5% CaCl₂ at 70°C were 2.5 times firmer than diced tomatoes treated with CaCl₂ at room temperature. This improvement in texture by treating with CaCl₂ at elevated temperatures was only apparent when the tomatoes received a subsequent 100°C treatment. Heating tomatoes to 70°C either before or after the CaCl₂ treatment also improved firmness through a subsequent high-temperature treatment, but to a lesser extent than heating during the CaCl₂ treatment. These results are consistent with the model that heating to 70°C greatly increases PME activity, leading to extensive pectin de-esterification and increased calcium cross-linking of the pectins in the middle lamella. Production of thermally processed diced tomatoes with improved firmness should be possible by increasing the temperature during and after calcium treatment.     

Performance of Cinta Senese pigs and their crosses with Large White 2. Physical, chemical and technological traits of Tuscan dry-cured ham

Technological, chemical and physical traits of cured ham from Cinta Senese and Large White pigs, and their crosses were investigated. Hams were obtained from 29 Cinta Senese (CS), 29 Large White × Cinta Senese (LW × CS) and 12 Large White (LW) pigs, fed a commercial mixture. Sensory and chemical–physical analysis was performed on a sample-slice and on muscles (Biceps femoris – BF; Semimembranosus – SM; Semitendinosus – ST) and subcutaneous fat. CS showed the highest trimming loss and the lowest salting loss. Hams of CS pigs scored higher for fatness than those of LW pigs, LW × CS showing intermediate values. On sample-slice, CS exhibited higher firmness, redness and marbling of lean, and greater fat extension than LW, with crosses having intermediate scores. Muscle moisture was lowest in CS, while both SM and BF from LW had the highest percentage of protein and the lowest of ash. CS showed higher intramuscular fat content than LW × CS and LW. Shear force of BF was higher in CS than in LW × CS and LW. With respect to LW, CS had lower values of L^* in muscles, and higher values of a^* in subcutaneous fat. Subcutaneous fat of CS contained less SFA and more MUFA than LW × CS and LW.     

Rheology of scleroglucan dispersions

The rheological properties of a scleroglucan, industrially produced by Sclerotium rolfsii, either in aqueous or dimethylsulfoxide (DMSO) dispersions at concentrations (c) ranging from 0.01% to 1.5% (w/w) were determined by using Cannon–Fenske capillary viscometers and a dynamic stress rheometer with plate-and-cone geometry under steady shear flow, small amplitude oscillatory shear and creep. The intrinsic viscosity [η] in water and DMSO was found to be equal to 12.1±0.3 and 4.6±0.3 dl/g, respectively. Despite the creep and oscillatory tests pointed out the presence of more or less strong molecular entanglements resulting in a three-dimensional network for c0.35% (w/w), the steady shear flow ones using a stress increasing exponentially with time showed a Newtonian behaviour at low enough shear rates, a pseudo-plastic one in the middle shear rate range and a second Newtonian plateau at very high shear rates. The Cross equation was capable of describing the rheological behaviour of the aqueous scleroglucan dispersions both in the sol and gel domain for shear rates and scleroglucan concentrations in the ranges 5×10⁻⁵–3.5×10³ s⁻¹ and 0.15–1.5% (w/w), respectively; while the Ostwäld-de-Waele model well fitted the apparent viscosity of the scleroglucan dispersion in DMSO at c=1% (w/v) and ranging from 2.5 to 180 s⁻¹.     

Application of a monoclonal-based immunoassay for the determination of imazalil in fruit juices

A monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of imazalil [(RS)-1-(β-allyloxy-2,4-dichlorophenylethyl)imidazole] in apple, tomato and orange juice samples. From an imazalil hapten, which mimics the analyte structure, several monoclonal antibodies were obtained. An ELISA in the conjugate-coated format was developed and optimized using the antibody showing the highest sensitivity. For standards, the detection limit of the ELISA was 0.2 nM (0.06 ng ml^-1), with an I₅₀ value of 1.6 nM (0.5 ng ml^-1). The study of the influence of matrices on assay reliability indicated that the ELISA could determine imazalil in fruit juices at the low ng ml^-1 level simply by diluting the sample, without any clean-up or concentration step. Recovery and precision of the method were evaluated by spiking juice samples with imazalil in the 10-500 ng ml^-1 range. The mean recovery from fruit juices was 97% and the mean coefficient of variation was ∼20%. In addition to being precise and accurate, the method has proved to be simple and sensitive, with a quantification limit well below the maximum residue limits for imazalil in these matrices.     

Prediction of moisture transfer parameters for microwave drying of lactose powder using Bi–G drying correlation

The mass transport properties characterising the drying of lactose powder were determined using a correlation proposed by Dincer and Hussain [Dincer, I. & Hussain, M. M. (2004). Development of a new Bi–Di correlation for solids drying. International Journal of Heat and Mass Transfer, 47, 653–658]. Experimental moisture content data for lactose samples dried under convective, microwave, combined convective-microwave and combined vacuum-microwave conditions were collected. The drying coefficients and lag factors were calculated from the experimental data and incorporated into the model. The Bi numbers were in the range 0.185–439, and moisture diffusivities and diffusion coefficients in the range from 0.135 × 10⁻⁹ to 102 × 10⁻⁹ and from 0.194 × 10⁻⁶ to 118 × 10⁻⁶ m/s, respectively. The predicted moisture profiles showed adequate agreement with the experimental observations, with the average error between experimental and predicted results being ±13.7%.     

Extraction of polycyclic aromatic hydrocarbons from cookies: A comparative study of ultrasound and microwave-assisted procedures

The chromatographic determination of 15 polycyclic aromatic hydrocarbons (PAHs) in cookies has been improved in order to obtain a fast method with a low limit of detection through the combination of microwave-assisted extraction (MAE), oil saponification and solid-phase extraction clean-up before the injection of purified extracts in a C18 201TP52 (5 µm, 250  × 2.1 mm) column. Using acetonitrile-water as mobile phase, with a 50% to 95% w/w acetonitrile gradient for a fixed flow of 0.250 ml min^-1, 15 PAHs were separated in 45 min. The column temperature was maintained at 15°C; and fluorimetric detection was made at a fixed excitation wavelength of 264 nm and emission measurements at the best wavelength for each analyte, from 352 nm for 11H-benzo[b]fluorene to 500 nm for indeno[1,2,3-c,d]pyrene. Recoveries for all 15 PAHs varied between 96  ± 4 and 105%  ± 4%; and the limits of detection ranged from 0.015 ng g^-1 for chrysene to 0.7 ng g^-1 for phenantrene. Results were compared with those obtained by conventional Soxhlet extraction during 8-h refluxing with toluene, demonstrating that the methodology proposed is appropriate to quantify PAHs in cookies. Furthermore, the microwave-assisted method was faster and used less solvent than the conventional and ultrasound-assisted methods. The extraction time was reduced to 9 min compared with the 8 h required for Soxhlet extraction and 60 min required for ultrasound-assisted treatment, and the solvent consumption has been reduced to 25 ml compared with the 155 and 90 ml required using Soxhlet and ultrasound, respectively.     

Physicochemical changes of sweet cherry fruits related to application of gibberellic acid

The influence of gibberellic acid on the physical and chemical properties of sweet cherry fruits during ripening (development of fruit colour) and at fruit maturity (firmness of fruits, cracking index, water uptake, soluble solids content, total acidity, fruit dimensions) of three sweet cherry cvs. ‘Van', ‘Sunburst' and ‘Elisa' grown in a climate with frequent rainfall during fruit maturation were studied. Fruits of cv. ‘Elisa' were prematurely picked because of cracking. A significant main effect of GA₃ treatment and significant main effect of cultivars were established in fruit colour development. The means of firmness and soluble solids content were systematically higher for the cherries of ‘Van' and ‘Sunburst' treated with GA₃ but they were not significant at =0.05. The fruit cracking was significantly smaller for GA₃-treated fruits of the cv. 'Sunburst' after 4 h in water. Gibberellic-treated fruits of both cultivars were larger in fruit weight than untreated fruits; the differences were significant at =0.10. Fruit dimensions: height, width and thickness of both cultivars were significantly affected by GA₃ treatment. The response of sweet cherry fruits to GA₃ spraying depended on the properties of the cultivar.     

N-methyl carbamate pesticide residues in conventional and organic infant foods available on the Canadian retail market, 2001-03

Seven parent N-methyl carbamate insecticides, in addition to two transformation products of aldicarb (aldicarb sulfoxide and aldicarb sulfone), and a single transformation product of carbofuran (3-hydroxycarbofuran) were measured in infant and junior foods available on the Canadian retail market between 2001 and 2003. Carbaryl and methomyl were the only analytes present at levels above the limits of detection in juice, cereals, fruit, vegetables or meat samples analysed. Carbaryl was the most frequently (7.6%) detected compound and concentrations ranged from 0.6 to 18 ng g^-1. Detectable levels of carbaryl were most frequently found in foods prepared with fruit. Methomyl was detected (0.8 ng g^-1) in one chicken with broth sample analysed in the present study. In all cases, the concentrations observed were orders of magnitude below the maximum residue limits established for these compounds in the corresponding raw food commodities in Canada (100-10 000 ng g^-1). Dietary intakes of carbaryl and methomyl based on the consumption of infant foods tested ranged between 0.2-343 and 0.4-2.0 ng kg^-1 body weight day^-1, respectively.     

MICROBIOLOGICAL PROFILE OF MURCHA STARTERS AND PHYSICO-CHEMICAL CHARACTERISTICS OF POKO, A RICE BASED TRADITIONAL FERMENTED FOOD PRODUCT OF NEPAL

Poko is a traditional rice based fermented food of Nepal prepared using murcha as the starter. The microbiological evaluation of eleven murcha starters showed that the lactic acid bacteria and yeast were dominant at 5×10⁵ to 1.0×10⁹ cfu g^-1 range while fungi were present at 2×10⁵ to 1.0×10⁷ cfu g^-1. Coliforms (1×10² to 1.4×10⁵ cfu g^-1), E. coli (1×10³ cfu g^-1), and. S. aureus (1×10² g^-1) were present in some of the murcha starters. Bacillus cereus was absent in all the starters. The microbial succession during poko fermentation suggested that it was primarily a mixed fermentation of yeasts, molds and lactic acid bacteria. The quality poko product obtained after two days and three days of fermentation at 30°C had a pH, acidity, reducing sugar, total sugar, and alcohol in the range of 3.2-3.0, 1.1-1.3 (% LA), 14.4-15.6 (%), 14.6-18.2 (%) and 1-1.6 (%) respectively. These critical ranges of biochemicals in the poko, due to the fermentation process imparted desirable organoleptic characteristics to the product. Saccharomyces cerevisiae, Candida versatilis, Lactobacillus spp, Pediococcus spp and Rhizopus spp were the dominant microorganisms identified from the poko fermentation. The results suggest that the quality of poko depends upon the microbial flora of the traditional murcha starters.     

Effect of Blanch Temperature on Kinetics of Thermal Softening of Carrots and Green Beans

Cut green beans and diced carrots were blanched at 100°C and 74°C then canned and processed for 5 min to 300 min at 100°C. In every case the rate of thermal softening was consistent with the two substrate first-order kinetic theory of thermal softening of vegetable tissue. The low temperature blanch caused some changes in the apparent firstorder rate constants for both substrates, but the major difference was a much higher intercept of the extrapolated substrate S_S line on the firmness axis. We define S_S at zero process time as the “thermal firmness value” because it is a good indicator of what the firmness of the vegetable will be after canning.