The influence of enzymatic treatment of mash on the analytical composition of apple juice

Five apple juices were produced on a pilot scale by crushing the fruit, treating the mash with pectolytic enzymes, pressing, extracting water from the pomace, pasteurization, treatment of the juice with enzymes, combined gelatin/silica sol fining and final ultrafiltration. The temperature of the mash treatment was either ambient or one of 30, 40, 50 or 60 °C, in order to test whether this led to different compositional changes in the corresponding juices. The main emphasis was put on detection of D -galacturonic acid as the indicator substance for the extent of the enzymatic treatment. In the pasteurized raw juices after pressing we found values from 226 to 398 mg L⁻¹. A distinct increase of the galacturonic acid levels could be observed during the clarification steps. Enzymatic juice treatment raised the concentrations to 580–720 mg L⁻¹. After ultrafiltration, final values of 790–1100 mg L⁻¹ were measured. Generally, the highest values were found in the 50 °C sample, which is the optimum temperature for pectinase activity. This was also true for the colloid concentrations and polyphenols. The influence of the temperature of the enzymatic mash treatment on other characteristic juice parameters like total titratable acidity, density, sugar, and minerals concentrations was low.     

Thermal Conductivity of Pear, Sweet-cherry, Apricot, and Cherry-plum Juices as a Function of Temperature and Concentration

ABSTRACT:  The thermal conductivity of 4 fruit (pear, sweet-cherry, apricot, and cherry-plum) juices was measured with a coaxial-cylinder (steady-state) technique. Measurements were made, temperature range 20 to 120 °C, at concentrations between 12.2 and 50 °Brix. The uncertainty of the thermal conductivity measurements was estimated to be less than 2%. A semitheoretical method for the prediction of thermal conductivity of juices was proposed. It was found that the prediction Model IV,  λ ( T , x )/λ ( T ₀, x ) = ( T / T ₀) ⁿ   , where  λ  is the thermal conductivity, x is the concentration, and T is the temperature, developed in this work can be adopted with satisfaction. The thermal conductivity of juices can be predicted just by knowing the thermal conductivity  λ₀  at a reference temperature   T ₀  .     

Antimicrobial activity of nisin incorporated in pectin and polylactic acid composite films against Listeria monocytogenes

An extruded composite food packaging film containing pectin, polylactic acids (PLAs) and nisin was developed to inhibit Listeria monocytogenes . The mechanical properties and surface structure of the film were also examined. Cells of L. monocytogenes were reduced by 2.1, 4.5 and 3.7 log units mL⁻¹ by the pectin plus PLA (pectin/PLA) film containing nisin (1000 IU mL⁻¹ of tested liquid) in Brain Heart Infusion (BHI) broth, liquid egg white and orange juice, respectively, after 48 h at 24 °C. Pectin played an important roll in embedding nisin into the film. The pectin/PLA film had a similar stiffness but lower tensile strength, elongation and fracture energy than the pure PLA film. These data suggested that nisin incorporated into the pectin/PLA film was an effective approach to reducing L. monocytogenes in a typical growth medium (e.g. BHI broth) as well as in foods (e.g. orange juice and liquid egg).     

Singlet Oxygen Quenching Activities of Various Fruit and Vegetable Juices and Protective Effects of Apple and Pear Juices against Hematolysis and Protein Oxidation Induced by Methylene Blue Photosensitization

ABSTRACT:  Effects of various fruit and vegetable juices on rubrene oxidation induced by a chemical source of singlet oxygen in a microemulsion system have been studied. The singlet oxygen quenching activities of fruit and vegetable juices were greatly different with different juices. The apple and pear juices exhibited the highest antioxidative activity among the tested juices in singlet oxygen–induced rubrene oxidation, showing 56.69% and 59.34% inhibition, respectively. The grape, kumquat, red cabbage, and spinach juices also showed relatively strong antioxidative activity against singlet oxygen–induced rubrene oxidation. Lemon juice showed the least activity, resulting in 0.63% inhibition of rubrene oxidation. The singlet oxygen quenching activities of 1 mL of apple and pear juices were equivalent to 33.97 and 34.64 mg ascorbate, respectively. Singlet oxygen quenching activities of juices had very low correlation with both ABTS radical scavenging activity ( R ²= 0.11) and total phenolic contents ( R ² < 0.1). However, a high correlation ( R ²= 0.66) was found between the ABTS radical scavenging activities and total phenolic contents of juices. The apple and pear juices also significantly inhibited both erythrocyte lysis and protein oxidation induced by fluorescence light illumination in the presence of methylene blue. Electron spin resonance (ESR) spectroscopy data showed that the protective activities of these juices against biological damages induced by photodynamic ways were, to at least some extent, due to their singlet oxygen quenching abilities. This represents first report on the singlet oxygen quenching activities of the apple and pear juices, and their protective activities against photodynamically induced biological damages.     

INACTIVATION OF BACTERIAL SPORES BY COMBINED ACTION OF HYDROSTATIC PRESSURE AND BACTERIOCINS IN ROAST BEEF

Foodborne bacterial spores are normally resistant to high hydrostatic pressure; however, at moderate pressure, they can be induced to germinate and outgrow. At this stage, they can be killed by bacteriocin-based biopreservatives (BP-containing pediocin and nisin at 3:7 ratio; BP_X, BP + 100 μg/mL lysozyme; BP_Y, BP_X+ 500 μg/mL Na-EDTA). Based on this principle, spores of the meat spoilage organism, Clostridium laramie (1–2 × 10² spores/bag) alone or a mixture of four clostridial spores (5 × 10³ spores/bag), Clostridium sporogenes, Clostridium perfringens, Clostridium tertium, and Clostridium laramie, were inoculated in roast beef in the presence of 5000 AU/g of bacteriocin-based biopreservatives. The roast beef samples were subjected to hydrostatic pressure (HP) at 345 MPa for 5 min at 60C and stored at 4 or 12C for 84 days or at 25C for 7 days. The HP treatment of roast beef samples inoculated with a mixture of clostridial spores could be stored for 42 days at 4C. The HP in combination with either BP_X or BP_Y extended the shelf-life of roast beef up to 7 days at 25C. The combined treatment of HP and BP controlled the growth of C. laramie spores and extended the shelf-life of roast beef for 84 days when stored at 4C.     

Mechanism of inactivation of heat-tolerant spores of Bacillus stearothermophilus IFO 12550 by Rapid Decompression

The effect of three rapid decompression methods to clear the mechanism of inactivation of heat tolerant spores of Bacillus stearothermophilus IFO 12550 was investigated. Pressurization of the spores at 200 MPa and 75°C for 60 min caused a kill of 10⁴ CFU/mL by the link-motion system but the nonrotational rod valve and E.G. seal methods gave a kill of about 10³ CFU/mL. Sterilization was due to the physical breakdown of spore coat, and was induced by its physical permeability of water at high pressure and temperature. Rapid decompression by the link-motion system at 200 MPa decreased the D-value of the spores from 3000 min (100°C, one atmosphere) to 6 min, 11 min, and 17 min at 95, 85, and 75°C, respectively.     

Development of a simple model based on chemical kinetics parameters for predicting respiration rate of carambola fruit

The respiration model was parameterised with experimental data obtained at temperatures 10, 15, 20, 25 and 30 °C by the closed system. Reaction orders of O₂ and CO₂ determined for respiration rate are 0.912 and −0.24, respectively. Estimates of A and E _a for rate coefficient are 5.219 _× 10¹⁰ h⁻¹ and 61.397 kJ mol⁻¹, respectively. The reliability of the model was verified against new data generated from 18 °C. An enzyme kinetics based model was likewise built and verified as a contrast. Verification results indicate that the chemical kinetics model performs very well and has superiority over the enzyme kinetics one. This study demonstrates that chemical kinetics can be used to underpin the development of simple respiration model and should facilitate the prediction of respiration rate for the carambola fruit in practice.     

Model of the Inactivation of Bacterial Spores by Moist Heat and High Pressure

ABSTRACT: Formulae for the prediction of inactivation and accumulated lethality of bacterial spores under moist heat and high pressures were derived on the basis of classic thermodynamic and kinetics principles. The capability of the model to describe the inactivation of bacterial spores was verified using 2 independent data sets corresponding to Clostridium botulinum processed at 60°C to 75°C and Bacillus stearothermophilus processed at 92°C to 110°C. Both sets included pressures between 5 × 10⁸ Pa and 7 × 10⁸ Pa. The equation fit explained more than 86% of the variation of the rate constant data. The developed equations establish a strong foundation on which to compare high-pressure processing treatments of different systems. This is especially useful because most systems have different transient temperature-pressure conditions.     

FLOW BEHAVIOR OF CLARIFIED ORANGE JUICE AT LOW TEMPERATURES

This paper presents a study of the rheological behavior of clarified and depectinated orange juices, with different soluble solid contents, at temperatures just above their freezing point. The rheological behavior of depectinated and clarified orange juice was determined for a wide range of soluble solid contents (10–65.8° Brix) and temperatures ( − 15 to 30C). The results indicated that the samples behave like a Newtonian fluid. The effect of temperature on the juice can be described with an Arrhenius-type equation. It was found that the activation energy for viscous flow was in the range of 9.4 to 59 kJ/mol, depending on the concentration. The effect of the soluble solid content can be described by an exponential-type equation. Finally, an equation in which dynamic viscosity depends on temperature and soluble solids content gives the following expression: η =  1  ×  10 ^{- 15} exp(0.12C  +  9021/T), where T in Kelvin, C in °Brix, and viscosity in mPa·s.

PRACTICAL APPLICATIONS

It is necessary to know the relationship between viscosity with temperature and concentration, since knowledge of these parameters is of vital importance in the manipulation, calculation and design of all those unit operations during the process, mainly those based on heat and quantum transfer.     

Storage stability of a stimulant coconut water–acerola fruit juice beverage

The objective of this work was to study the stability of a beverage formulated with acerola fruit juice and green coconut water with added caffeine. The beverage was prepared with 25% acerola pulp, 75% green coconut water and sugar up to 12°Brix, and caffeine (125 mg L⁻¹), heat processed at 90 °C for 30 s and packed in 250-mL glass bottles. Chemical, physicochemical, microbiological and sensory analyses of the beverage were performed just after processing and during 6 months of storage at room temperature (27 °C). The vitamin C content decreased significantly throughout storage, from 399.5 to 189.6 mg 100 mL⁻¹, although it has remained relatively high. The anthocyanins initially present (0.025 mg 100 mL⁻¹) were completely lost during the storage at a mean rate of 4 μg 100 mL⁻¹ month⁻¹. The product was microbiologically stable during storage. Colour changes were also observed with absorbance at 420 nm, with average values ranging from 0.19 to 0.24. However, according to the sensory analyses the product was acceptable during the 6 months of storage, presenting sensory scores (colour, taste and global acceptance) from 6.5 to 5.5, which suggests its potential for market.     

EFFECT OF NITRITE AND STORAGE TEMPERATURE ON THE ORGANOLEPTIC QUALITY AND TOXINOGENESIS BY Clostridium botulinum IN VACUUM-PACKAGED SIDE BACON

The effect of nitrite and storage temperature and toxinogenesis by Clostridium botulinum in vacuum-packed side bacon was investigated. In two series of experiments (A & B) bacon packs were prepared with levels of 0, 50, 100, 150 and 200 ppm nitrite and inoculated with C botulinum at 10² spores/g and 10⁴ spores/g. Packs A were incubated at 20 and 30° C and packs B at 30°C only. Both were held for a maximum of 32 days and analyzed for toxin at intervals of 2, 4, 8, 16 and 32 days. At 20°C none of the controls without nitrite was found to be toxic after 32 days. At 30°C inhibition of toxin formation at the higher nitrite levels was observed at 32 days. Organoleptic evaluation of the bacon packs stored at 30° C showed about one-third of the toxic samples examined were acceptable to the panel.     

Effects of high pressure treatment on the quality and storage of kimchi

The effects of high pressure treatment on the microflora and storage of kimchi were investigated. In a bacterial suspension, numbers of Lactobacillus plantarum were reduced by 6 logs by 500 MPa, at 25 °C for 10 min. Kimchi juice did not alter the rate of inactivation of lactic acid bacteria by high pressure treatment. There was no change in the texture of kimchi subjected to a pressure of 400 MPa, but an increase in cutting force was observed at 600 MPa. When kimchi was pressurized at 400 MPa for 10 min at 25 °C and subsequently stored at 20 °C for 4 weeks, the total number of viable cells stayed at 10³ CFU mL⁻¹. High pressure treatment above 400 MPa prevented excessive acidification that typically occurs during the extended storage of kimchi. The inflation of pouches as a result of accumulated carbon dioxide was also prevented by high pressure treatment. Although colour changes were accelerated by high pressure treatment, this study demonstrates that high pressure treatment can be used to control overripening during the distribution and storage of kimchi products.     

EVALUATION OF BACTERIOLOGICAL QUALITY IN SELECTED COMMERCIAL INFANT FORMULAS AVAILABLE IN POLAND AND EGYPT

One hundred samples of commercial infant formula bought in shops in the Poznan region (Poland) and Cairo region (Egypt) were investigated. Samples were analyzed for aerobic plate counts (APC), total Bacillus cereus (TBC), and incidences of Bacillus spp. and coliforms. The mean APC and TBC did not show any important variation with country, being practically the same in products bought in Poland and Egypt. All commercial infant formula analyzed immediately after opening were of satisfactory bacteriological quality, exhibiting APC lower than 10⁴ CFU g⁻¹ (mean 4.9 × 10²) and TBC lower than 10³ CFU g⁻¹ (mean 1.1 × 10²). However, 60% of the examined fruit juice and ready-to-feed infant formula presented TBC above the recommendation safety limit after storage at 22C for 72 h and at 35C for 48 h. In most cases the mean log APC and TBC were highest (P > 0.05) for fruit juice and ready-to-feed infant formula stored at elevated temperature (35 ± 1C).     

Recipes for antimicrobial wine marinades against Bacillus cereus, Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica

ABSTRACT:  We have evaluated bactericidal activities against Bacillus cereus , Escherichia coli O157:H7, Listeria monocytogenes , and Salmonella enterica of several antimicrobial wine recipes, each consisting of red or white wine extracts of oregano leaves with added garlic juice and oregano oil. Dose-response plots were used to determine the percentage of the recipes that resulted in a 50% decrease in colony-forming units (CFU) at 60 min (BA₅₀). Studies designed to optimize antibacterial activities of the recipes demonstrated that several combinations of the naturally occurring plant-derived ingredients rapidly inactivated the above mentioned 4 foodborne pathogens. We also showed that (a) incubation temperature affected activities in the following order: 37 °C > 21 °C > 4 °C; (b) varying the initial bacterial concentrations from 10³ to 10⁴ to 10⁵ CFU/well did not significantly affect BA₅₀ values; (c) storage of 3 marinades up to 2 mo did not change their effectiveness against Salmonella enterica ; and (d) polyphenolic compounds isolated by chromatography from red wine exhibited exceptional activity at nanogram levels against 2 strains of Bacillus cereus . These observations suggest that antimicrobial wine formulations have the potential to improve the microbiological safety of foods.     

Osmotic Dehydration of Tomato in Sucrose Solutions: Fick's Law Classical Modeling

ABSTRACT:  Osmotic dehydration of tomato was modeled by the classical Fick's law including shrinkage, convective resistance at the interface and the presence of water bulk flow. Tomato slices having 8 mm thickness were osmotically dehydrated in sucrose solutions at 50, 60, and 70 °Brix and at 35, 45, and 55 °C. Other experiments were done in a 70 °Brix sucrose solution at 35 °C with tomato slices of 4, 6, and 8 mm thickness and at different motion levels (velocities 0, 0.053, and 0.107 m/s). Tomato weight, water content, and °Brix of the products were measured as a function of processing time (20, 40, 80, 160, and 320 min). Results showed that temperature, concentration, thickness, and solution movement significantly influenced water loss and sucrose gain during the osmotic dehydration of tomato. The model predicted the modifications of soluble solid content and water content as a function of time in close agreement with the experimental data. Experimental Sherwood number correlations for sucrose and water were determined as Sh _s = 1.3 Re ^0.5 Sc _s^0.15 and Sh _w = 0.11 Re ^0.5 Sc _w^0.5, respectively. The effective diffusion coefficients of water (4.97 10⁻¹¹– 2.10 10⁻¹⁰ m²/s) and sucrose (3.18 10⁻¹¹– 1.69 10⁻¹⁰ m²/s) depended only on temperature through an Arrhenius-type relationship.     

COLOR AND VITAMIN C CONTENT IN MANDARIN ORANGE JUICE AS AFFECTED BY PACKAGING MATERIAL AND STORAGE TEMPERATURE

Mandarin orange (Citrus reticulata) juice was packed in two different non-transparent cartons made of polyethylene, cardboard and (1) aluminum foil (Tetrapak ^® ) or (2) ethylene vinyl alcohol copolymers (Pure-pak ^® ) and was stored at 4C or room temperature (25  ±  3C). During the shelf life of these juices (35 days), changes in the headspace gas composition, vitamin C and CIEL*a*b* color coordinates were evaluated. In addition, a consumer panel evaluated the sensory color of the juices. Mandarin orange juices darkened and ascorbic acid content decreased with storage time. Type of carton and storage temperature played a predominant role in determining the final juice quality, with Tetrapak ^® carton providing the juice with the best quality (intense orange color and high vitamin C content and consumer preference) throughout their shelf life.

PRACTICAL APPLICATIONS

This study was a clear example of how research can help real food companies in selecting the right materials for their production lines. In this particular case, the results presented show how Tetrapak^® packaging led to a final mandarin orange juice of higher quality compared to Pure-pak^® packaging. Therefore, citrus processing companies have some scientific data comparing the behavior of these two types of non-transparent cartons. Besides, the companies manufacturing these cartons also have some information about their materials and can use it to improve them.     

Effect of nisin and high temperature pasteurization on the shelf-life of whole milk

Two experiments were conducted to assess the effectiveness of nisin on the keeping quality of pasteurized whole milk. After pasteurization, milk samples were stored at 10°C and samples were analysed at intervals for total plate count (TPC), Lactobacillus count, calcium ion concentration, pH and total acidity (TA). In the first experiment nisin was added to milk samples in the range 0 to 50 IU ml^-1 prior to pasteurization at 72°C for 15 s. AH concentrations of nisin used were effective in controlling microbial growth. Milk containing 40 and 50 IU ml^-1 nisin had not spoiled after 41 days' storage compared to spoilage time of 14 days for the control milk. In the second experiment 40 IU ml^-1 of nisin was combined with three 'pasteurization' processes: 72°C for 15 s, 90°C for 15 s and 115°C for 2 s. The milk processed at 72°C for 15 s with nisin showed an increased keeping quality of about 7 days compared with the control and showed a significantly lower count for Lactobacillus. In contrast, nisin had a much greater effect on TPC counts in the milk pasteurized at 90°C for 15 s, and after 28 days' storage at 10°C the milk was still acceptable. Milks treated both with and without nisin at 115°C for 2 s were microbiologically acceptable after 28 days, with counts less than 10 ml^-1. However, the milk with nisin was superior in flavour, as no noticeable off-flavours were apparent after 32 days. All these results are consistent, as shown by the microbiological and chemical analyses. Addition of nisin to milk prior to pasteurization provides an opportunity to achieve extended shelf-life in regions with poor refrigeration.     

Microbiological quality of ice creams commercialized in some cities in the state of Rio de Janeiro, Brazil

The microbiological quality of 60 ice cream samples of three commercial brands (A, B and C) of various flavours, commercialized in some towns in the State of Rio de Janeiro, Brazil, was evaluated. Total bacteria count (TCB), coliforms at 35°C (CT), coliforms at 44°C (CF) and presence of Staphylococcus aureus were performed on all samples. TCB ranged from 2.0 × 10 ² to 6.9 × 10 ⁵ cfu/mL, CT from < 3–≥ 2400 MPN/mL, CF from < 3–1100 MPN/mL and S. aureus from < 10–1.4 × 10 ⁶ cfu/mL. The level of bacterial contamination found in this study reflects the unhygienic conditions prevalent in manufacturing and storage of ice creams. Actions are thus necessary by the Brazilian regulatory agencies to require the ice cream processing plants to adopt quality guarantee systems, such as good manufacturing practices and hazard analysis and critical control points system.     

Production of Enterotoxin-B in Cured Meats

SUMMARY— A variety of laboratory cured hams were inoculated with 10³−10⁶ cells of S. aureus strain S-6 and incubated at 10, 22 and 30°C anaerobically for up to 16 weeks. Enterotoxin-B was detected by gel-diffusion in hams with original pH over 5.30, up to 9.2% NaCl (brine) and 0.54 ppm undissociated nitrous acid. There was better toxin production at 30° than at 22° or 10°C. Toxin was detected at 10°C after at least 2 weeks incubation and in most samples after 8 weeks when pH was greater than 5.6. Toxic hams had more than 4 × 10⁶ cells/g. Contaminants were always less than 10⁵/g. Tween 80 inhibited toxin production at 30° but not at 10°C. Toxic hams looked normal even after 2 months incubation at 10°C.     

Inhibition of Alicyclobacillus acidoterrestris spores by natural compounds

The aim of this study was to evaluate the antimicrobial effectiveness of some natural compounds (cinnamaldehyde, eugenol, limonene) and sodium benzoate against two strains of Alicyclobacillus acidoterrestris (c8 and γ4). The antimicrobial compounds (10–500 ppm) were solved in malt extract broth, inoculated separately with 10³ spores mL⁻¹ of each strain; the samples were incubated at 44 °C and the outgrowth of spores was evaluated every day by measuring the absorbance of the medium at 420 nm; inoculated samples without active compounds were used as controls. The results pointed out that limonene was not effective in inhibiting the outgrowth of A. acidoterrestris spores; 100 ppm of cinnamaldehyde or sodium benzoate slowed the spore germination, whereas 500 ppm of eugenol inhibited the growth of microbial targets for 13 days. Strain c8 was more resistant than isolate γ4 and cinnamaldehyde was the most effective compound in inhibiting the germination of A. acidoterrestris spores.