QUALITY OF ORANGE JUICE DRINK SUBJECTED TO A PREDICTIVE MODEL-BASED PASTEURIZATION PROCESS

The utility of a previously developed predictive model for the decimal reduction time ( D _72C) of Salmonella Typhimurium (ATCC 13311) in citrus systems was validated by establishing a pasteurization process ( P _72C) for Philippine native orange juice drink (POD). Quality characteristics of the pasteurized POD were evaluated and used as bases for assessing the utility of the developed model. The ^p P _72C for POD was calculated by multiplying the model-generated D _72C of the reference strain with the recommended order of lethality ( m ) of 5.00 log₁₀ cycles. A ^a P _72C was likewise calculated based on D _72C that resulted from actual thermal inactivation study of the reference strain on POD. Pasteurization resulted to PODs with significantly ( P <  0.05) altered color, microbial quality and sensory profile. Except for the overall quality, differences in the consumer acceptance of various unpasteurized and pasteurized PODs quality characteristics were found to be not significant.

PRACTICAL APPLICATIONS

A mathematical model was developed to estimate the thermal death times of the pathogen Salmonella Typhimurium (ATCC 13311) from the pH, titratable acidity (% citric acid) and soluble solid (°Brix) values of suspending citrus systems. In this study, the utility of this model in establishing a pasteurization process for a test orange juice drink was determined. As the establishment of specific thermal process schedule for individual food products can be difficult, utilization of the validated model shall be a convenient alternative to the traditional but rigorous process.     

Determination of a process time for a new product: canned low acid artichoke hearts

In order to obtain a process time for canned low acid artichoke hearts, the heat resistance of Clostridium sporogenes PA 3679 in phosphate buffer (pH 7) and in artichoke puree (pH 5.2) was determined in the range of 100–118°C. D _T values in artichoke puree were determined by the most probable number and plate count methods. D _121°C values were deduced by extrapolation of the curves. An F 8.3/121 (see nomenclature section) target value of 1.8 min, equivalent to an F ₀= 2.5 min, was established considering a D _121°C value of 0.36 min for artichoke puree. The cold point for canned artichoke hearts in 1/2 kg (71.5x117 mm) cans was determined, a set of heat penetration and cooling curves were obtained and the values of the parameters ' j ' and ' f ' were found. A process time was deduced, 21.5 and 23 min of heating at 121°C, following the methods of Patashnik (1954) and Hayakawa (1970, 1974) respectively, in order to reach the F ₀ target of 2.5 min for this new canned food. This process was adequate, as the inoculated experimental pack test showed no altered cans out of 50 inoculated after 21.5 min of heating at 121°C.     

MEASUREMENT OF FLOW PROPERTIES OF FOOD SUSPENSIONS WITH A MIXER

Abstract. Flow properties of selected food suspensions (tomato puree, apple sauce, and apple pulp) were studied with a mixer. Power law constants for the suspensions were determined by employing an approximate method based on power correlations for mixers in the laminar flow regime. The studied suspensions cannot be characterized with narrow gap viscometers because of the size and segregation of the particles (formation of a dilute phase next to the rotor).     

Influence of vitamin E supplementation on spontaneous oxidized flavour of milk in dairy buffaloes

Twenty-four Murrah buffaloes (60 days pre-partum) were divided into four equal groups (T ₁ , T ₂ , T ₃ and T ₄ ) and were supplemented with 0, 1000, 1500 and 2000 IU α-tocopheryl acetate per day up to 30 days of lactation, and half of these doses from 30 to 60 days of lactation. Milk samples collected fortnightly were analysed for vitamin E, fat, and development of oxidized flavour, with and without copper addition by a panel of judges, and chemically by the thiobarbituric acid test. Scores for oxidized flavour ranged from 0 to 10 with 0–4 as definite, 5–7 as light and 8–10 having no defect. The α-tocopherol content in milk fat (µg/g) averaged 20.55, 25.56, 29.98 and 31.38 in T ₁ , T ₂ , T ₃ and T ₄ groups, respectively. The addition of Cu in the milk significantly increased milk fat oxidation. Better stability of milk in T ₃ and T ₄ groups was observed, which might be due to a higher level of milk α-tocopherol. Addition of 1500 IU α-tocopheryl acetate in the diet of buffaloes helped in improving the oxidative stability of milk.     

The effect of freezing and thawing on the magnetic resonance imaging parameters of water in beef, lamb and pork meat

A new multisample magnetic resonance imaging (MRI) technique has been used to measure the values of T ₁, T ₂, magnetization transfer (MT) rate and liquid proton density ratio ( M ₀%) for water in fresh and frozen–thawed beef, lamb and pork; four samples from the longissimus dorsi muscle of 25 different individuals per species were studied. The effect of two different chilling regimes, standard and tenderloin, were also studied. Standard chilled pork and lamb had a significantly higher M ₀% than tenderloin chilled samples, but there was no correlation between M ₀% and fresh weight; the differences in M ₀% are thought to be due to differences in MR (magnetic resonance)-visible water. There was a significant decrease in water content, T ₁ relaxation time, and a significant increase in MT rate in the frozen–thawed samples when all the data were pooled for each species. However, individual animals differed in the magnitude and direction of the change; this means that because of interanimal variation, measurements of MR parameters from a single sample of meat cannot be used at present to authenticate it.     

Artificial neural network modeling for temperature and moisture content prediction in tomato slices undergoing microwave-vacuum drying

ABSTRACT:  Inputs for ANN (multihidden-layer feed-forward artificial neural network) models were drying time ( t _{i + 1}), initial temperature ( T ₀), moisture content ( MC ₀), microwave power, and vacuum pressure. The outputs were temperature ( T _{i + 1}) and moisture content ( MC _{i + 1}) at a given t _{i + 1}. After training the ANN models with experimental data using the Levenberg-Marquardt algorithm, a two-hidden-layer model (25-25) was determined to be the most appropriate model. The mean relative error (MRE) and mean absolute error (MAE) of this model for T _{i + 1} were 1.53% and 0.77 °C, respectively. In the case of MC _{i + 1}, the MRE and MAE were 11.48% and 0.04 kg_water/kg_dry, respectively. Using temperature ( T _i ) and moisture content ( MC _i ) values at t _i in the input layer significantly reduced the computation errors such that MRE and MAE for T _{i + 1} were 0.35% and 0.18 °C, respectively. In contrast, these error values for MC _{i + 1} were 1.78% (MRE) and 0.01 kg_water/kg_dry (MAE). These results indicate that ANN models were able to recognize relationships between process parameters and product conditions. The model may provide information regarding microwave power and vacuum pressure to prevent thermal damage and improve drying efficiencies.     

Sorbic acid diffusivity in relation to the composition of high and intermediate moisture model gels and foods

The diffusivity at infinite diffusant dilution ( D ₀) of sorbic acid in high and intermediate moisture gels (with various substrates and water contents) and in three foods was evaluated. The determination of D ₀(25°C) was achieved by tridimensional diffusion in gels cubes or by monodimensional diffusion in infinite food columns. For the same substrate concentration by weight, D₀ values of sorbic acid in concentrated sugar solutions decreased slightly when the molecular weight of the sugar was increased. When a liquid substrate such as glycerol was used, D ₀ values referred to equal concentrations by weight, were higher than in sugar solutions. The diffusion of sorbic acid is related, as a first approximation, to the water content rather than to the water activity of the diffusion medium.     

Feasibility of utilizing bioindicators for testing microbial inactivation in sweetpotato purees processed with a continuous-flow microwave system

ABSTRACT:  Continuous-flow microwave heating has potential in aseptic processing of various food products, including purees from sweetpotatoes and other vegetables. Establishing the feasibility of a new processing technology for achieving commercial sterility requires evaluating microbial inactivation. This study aimed to assess the feasibility of using commercially available plastic pouches of bioindicators containing spores of Geobacillius stearothermophilus ATCC 7953 and Bacillus subtilis ATCC 35021 for evaluating the degree of microbial inactivation achieved in vegetable purees processed in a continuous-flow microwave heating unit. Sweetpotato puree seeded with the bioindicators was subjected to 3 levels of processing based on the fastest particles: undertarget process ( F ₀ approximately 0.65), target process ( F ₀ approximately 2.8), and overtarget process ( F ₀ approximately 10.10). After initial experiments, we found it was necessary to engineer a setup with 2 removable tubes connected to the continuous-flow microwave system to facilitate the injection of indicators into the unit without interrupting the puree flow. Using this approach, 60% of the indicators injected into the system could be recovered postprocess. Spore survival after processing, as evaluated by use of growth indicator dyes and standard plating methods, verified inactivation of the spores in sweetpotato puree. The log reduction results for B. subtilis were equivalent to the predesigned degrees of sterilization ( F ₀). This study presents the first report suggesting that bioindicators such as the flexible, food-grade plastic pouches can be used for microbial validation of commercial sterilization in aseptic processing of foods using a continuous-flow microwave system.     

Vane Yield Stress of Starch Dispersions

ABSTRACT: Yield stresses of 5% (wt/wt) cross-linked waxy maize, tapioca, and Amioca starch dispersions (SDs) were measured with the vane method at different rotational speeds ( N ). The static (σ_0S) and dynamic (σ_0d) yield stress values of each SD were measured before and after breaking down its structure under continuous shear, respectively. The difference (σ_0S - σ_0d) was associated with the stress required to break the internal bonds (σ_b). Values of total yield stress (σ₀=σ_0S) and σ_b, and shear rate were related by power law relationships. The contribution of viscous and network stresses were estimated from an energy balance model. Textural characteristics of the SDs were analyzed in a texture map.     

Confidence intervals for modeling anthocyanin retention in grape pomace during nonisothermal heating

ABSTRACT:  Degradation of nutraceuticals in low- and intermediate-moisture foods heated at high temperature (>100 °C) is difficult to model because of the nonisothermal condition. Isothermal experiments above 100 °C are difficult to design because they require high pressure and small sample size in sealed containers. Therefore, a nonisothermal method was developed to estimate the thermal degradation kinetic parameter of nutraceuticals and determine the confidence intervals for the parameters and the predicted Y (concentration). Grape pomace at 42% moisture content (wb) was heated in sealed 202 × 214 steel cans in a steam retort at 126.7 °C for > 30 min. Can center temperature was measured by thermocouple and predicted using Comsol software. Thermal conductivity (k) and specific heat ( C_p ) were estimated as quadratic functions of temperature using Comsol and nonlinear regression. The k and C_p functions were then used to predict temperature inside the grape pomace during retorting. Similar heating experiments were run at different time–temperature treatments from 8 to 25 min for kinetic parameter estimation. Anthocyanin concentration in the grape pomace was measured using HPLC. Degradation rate constant ( k _{110 °C}) and activation energy ( E_a ) were estimated using nonlinear regression. The thermophysical properties estimates at 100 °C were k = 0.501 W/m °C, Cp = 3600 J/kg and the kinetic parameters were k _{110 °C}= 0.0607/min and E_a = 65.32 kJ/mol. The 95% confidence intervals for the parameters and the confidence bands and prediction bands for anthocyanin retention were plotted. These methods are useful for thermal processing design for nutraceutical products.     

Whipping test for the determination of foaming capacity of protein: a collaborative study

A standard whipping test, which involved preparing a 0.5% protein dispersion, whipping the dispersion in a Kenwood Chef food mixer and measuring the foaming properties (foam expansion, FE; foam volume stability, FVS; foam liquid stability, FLS) was collaboratively evaluated. A total of sixty determinations was made involving six laboratories, each of which analysed five samples in duplicate. The repeatability coefficient of variation ( CV ₀) in the estimation of FE and FVS properties of proteins was 6.25%. The reproducibility coefficient of variation ( CV _X) for FE and FVS was 9.8%, excluding the FE value (i.e. 20%) for spray-dried albumen. The CV ₀ and CV _X values for FLS properties of proteins ranged from 7.4 to 13.4% and 17.2 to 24.6%, respectively. Thus, FE, FVS and FLS properties can be used for intralaboratory comparisons (e.g. to determine batch-to-batch variation in commercial protein products), whereas FE and FVS values are more reliable for inter-laboratory comparisons of the foaming properties of proteins.     

RHEOLOGICAL BEHAVIOR OF PROCESSED MUSTARD. II. STORAGE EFFECTS

Samples of processed yellow mustard with three different particle size distributions (slightly-coarse, standard, and fine) were prepared according to a standard formulation and pilot-plant replication of the commercial methodology and stored for 3 months at 5°C, 25°C, and 45°C. After 3-month storage at 45°C, all samples showed visible liquid separation (syneresis) and aggregation of colloidal particles, as indicated by increase in d _pop and decrease in % colloids. The fine milled samples exhibited syneresis and an increase in d _pop after 3-month storage even at 25°C. The bimodal distribution did not show significant changes as a result of aggregation. In general, increase in d _pop increased apparent viscosity (η _ap ), flow behavior index (n) from the Herschel-Bulkley model, and exponent n" from the loss modulus (G") power law equation. As d _pop increased, Bingham yield stress _o), plastic apparent viscosity (η _p ), shear stress constant (A) from the Weltman stress decay model, yield stress (_o) and consistency index (m) from the Herschel-Bulkley model, exponent n' from the storage modulus (G') power law equation, and minimum values of loss tangent (tan δ) decreased. In heterodisperse semi-solid foods such as processed mustard, the particle size distribution influences the structure (i.e., packing) and the rheological behavior. Therefore, time and temperature dependent instabilities such as syneresis may be minimized by controlling particle size distribution during processing.     

DYNAMIC MECHANICAL ANALYSIS OF MARINATED CHICKEN BREAST MEAT

Chicken breast muscle was marinated and tumbled in solutions of 7% NaCl and 1.2% of disodium pyrophosphate (DSPP), tetrasodium pyrophosphate (TSPP), tetrapotassium pyrophosphate (TKPP), sodium tripolyphosphate (STPP), or glass phosphate. Dynamic mechanical thermal analysis was used to measure storage modulus and Tan δ as samples were heated from 25 to 75C. For untreated samples, four thermal transitions were noted with the most significant transition at 55.8C. Addition of NaCl and phosphate reduced the number of distinct events, and decreased the major transition to temperatures around 46–48C. Uncooked, marinated samples had lower G' and Tan δ. Treated samples also showed an increase in G' over the 25–45C range. Heating caused the greatest changes in treated samples, with values of G'_75C and Tan δ_75C similar to untreated samples. Different phosphate types resulted in significant differences in G' and Tan δ values. G' values correlated well with Young's modulus, but not with Warner-Bratzler shear values or expressible moisture. Results are discussed in terms of changes in muscle proteins resulting from exposure to NaCl and phosphates, as well as to heat.     

RHEOLOGICAL INDICES OF FRUIT CONTENT IN JAMS: EFFECT OF FORMULATION ON FLOW PLASTICITY OF SHEARED STRAWBERRY AND PEACH JAMS

The effect of formulation factors on Casson yield values measured at low shear rates (0.08 ≤γ≤ 1.01s^-1) (σ₀₁) and at medium shear rates (2.58 ≤γ≤ 387.30s^-1) (σ₀₂) was analyzed in previously sheared strawberry and peach jams. Twenty three samples of each fruit jam were prepared according to a second order composite rotatable design. Composition ranges were: fruit content, 25–55%; soluble solids content, 60–70° Brix; added pectin in strawberry jams, 0.3–0.7% and in peach jams, 0.1–0.5%. Variation of σ₀₁ values in strawberry jams depended mainly on the interactions between fruit and soluble solids and between fruit and pectin, while in peach jams, it depended on fruit-soluble solids and soluble solids-pectin interactions. Patterns of change of σ₀₂ values with composition were similar to those observed for σ₀₁ in both strawberry and peach jams. Predictive power of σ₀₁ and σ₀₂ values for estimation of fruit content was low, but taken in conjunction with soluble solids content and total pectin values, 79.5% of the variability of fruit content in strawberry jams and 91.1% of same in peach jams could be explained.     

Rheology of Apple Sauce: Effect of Apple Cultivar, Firmness, and Processing Parameters

Shear rate-shear stress data of 54 samples of apple sauce and their serums were determined, and power law parameters were derived for the data. The samples were from two apple cultivars (Rome Beauty and Rhode Island Greening) that were stored to three firmness values and processed utilizing three finisher screen sizes and speeds. Serum samples were mildly non-Newtonian, while the sauce samples were highly non-Newtonian fluids. Analysis of variance showed that apple cultivar, apple firmness and finisher screen opening accounted for a large variation in sauce consistency, while regression analysis showed that pulp content was important for the magnitude of the sauce consistency.     

Adhesion modeling on rough low linear density polyethylene

ABSTRACT:  Food adhesion is an important attribute that could have both positive and negative ramifications depending on the application. Yet, its quantification remains cumbersome and as a consequence adhesion models are scarce. The effect of surface roughness, free energy, and ozone treatment on adhesion of rough low linear density polyethylene films was investigated. Adhesion was measured by a 180° peel strength test. The plastic films were roughened (surface roughness ratio, r , ranged from 1.00 to 1.15). Exposing the film to ozone treatment (0 to 300 s) modified its surface free energy, γ _s (32.4 to 37.9 mJ/m², respectively), and its polar component of the surface free energy, γ ^p _s (3.0 to 8.3 mJ/m², respectively). The films were coated with polyurethane capable of forming hydrogen bonds. Adhesion was found to be a function of the apparent contact angle of water, θ _{ap [water]}, surface roughness ratio, and surface free energy. The linear relationship between the apparent contact angle of water, θ _{ap [water]}, and γ ^p _s was incorporated in building an empirical model that quantifies peel strength as function of r and γ ^p _s . The model showed good agreement with experimental data, especially for longer ozone exposures and rougher surfaces. The empirical model provides insight into the relationships between surface roughness, surface energy, and adhesion. Quantifying these effects could facilitate reducing biofilm forming on food equipment, antisticking treatments, or easy peel packages, or reducing food residues adhering to the food packages and consequently minimize oxidation, off flavors, and waste.     

The rheological properties of ketchup as a function of different hydrocolloids and temperature

The flow properties of ketchup were assessed upon addition of commonly used food thickeners: guar, xanthan and CMC gum at three different concentrations (0.5%, 0.75% and 1%) and four temperatures (25, 35, 45 and 55 °C). The ketchup without supplementation served as a control. All ketchup formulations exhibited non-Newtonian, pseudoplastic behaviour at all temperatures and hydrocolloid levels. The Power-law and Herschel-Buckley model were successfully applied to fit the shear stress versus shear rate data. The flow behaviour indices, n and n' , varied in the range of 0.189–0.228 and 0.216–0.263, respectively. The consistency coefficients, k and k' , were in the range of 8.42–27.22 and 6.56–20.10 Pa s ⁿ , respectively. The addition of hydrocolloids increased the yield point (τ₀) and apparent viscosity of the ketchup in comparison to that of the control. The Arrhenius equation was successfully used to describe the effects of temperature on the apparent viscosity of the prepared formulations. The E _a value appeared in the range between 5492.6 and 21475.8 J mol⁻¹.     

The heat resistance of spores of Clostridium botulinum 213B over the temperature range 120 to 140°C

The heat resistance of spores of Clostridium botulinum strain 213B heated in phosphate buffer (pH 7.0) was determined over the temperature range 120 to 140°C using a computer controlled thermoresistometer. The predicted D _121°C value of approximately 0.13 min and z value of 11.0°C (obtained by linear regression) was close to the classical D_121°C of 0.2 min and z value of 10°C used in process calculations. These data indicated that, according to the heat resistance of this culture, the z value of C. botulinum can be considered constant over the whole range 120 to 140°C. This also provided support for the recommended classical process calculations, using a z value of 10.0°C, being adequate if extrapolated to 140°C.     

Lethal and Sublethal Action of Acetic Acid on Salmonella In Vitro and on Cut Surfaces of Apple Slices

ABSTRACT Antimicrobial action of acetic acid (AA) on Salmonella as affected by acid concentration, exposure time, culture age, and bacterial strains was investigated. Relative susceptibility of 6 Salmonella serovars to AA action was in the following order: S. bareilly > S. typhimurium > S. montevideo > S. poona > S. mbandaka > S. stanley. The stationary-phase cells of S. mbandaka were 100-fold more resistant to AA action than the log-phase cells. A mixture of Salmonella strains at a specified physiological stage should be used when testing the efficacy of the sanitizer treatment. Washing apple disks with NaOCl, H₂O₂, AA, or Na₃P0₄ greatly reduced the number of Salmonella and 30% to 40% of cells that survived were injured. Washing with a mixture of AA and H₂O₂ was the most effective in removing Salmonella from apple disks.     

Finding critical variables for food heating

It is important to identify intrinsic critical variables affecting the heating of products in processes aiming to achieve microbiological safety. The Taguchi method has enabled the identification of critical variables for heating of a complex canned product (spaghetti in a sauce) in an agitated process in a water immersion retort. Within the ranges tested one of eleven variables exerted a large effect upon product heating. The most important variable was the concentration of tomato puree in the sauce, which affected the process F ₀ by15–18 min between the two concentrations tested.