Factors controlling the growth of Clostridium botulinum types A and B in pasteurized, cured meats III. The effect of potassium sorbate

The growth of Clostridium botulinum types A and B spores, at 10¹ or 10³ per container, was studied in a pork slurry system containing nitrite (40 μg/g), sodium chloride (2.5, 3.5, 4.5% w/v) sodium isoascorbate (550 μg/g) at varying pH levels, with or without potassium sorbate (0.26% w/v), without heating and after two heat treatments (80°C for 7 min, and 80°C for 7 min + 70°C for 1 hr) followed by storage at 15, 17.5, 20 or 35°C for up to 6 months. At a given spore inoculum, potassium sorbate significantly decreased toxin production, as did increasing NaCl, decreasing pH or decreasing storage temperature. Heat treatment did not significantly affect spoilage or toxin production overall, but interacted significantly with some factors. The effect of sorbate was greater at 3.5% NaCl than at 2.5%, at pH values below 6.0, and at low storage temperature.     

Factors controlling the growth of Clostridium botulinum types A and B in pasteurized, cured meats

The effect of combinations of sodium chloride (2.5, 3.5, 4.5% w/v on water), sodium nitrite (100, 200, 300 μg/g), sodium nitrate (0, 500 μg/g), sodium isoascorbate (0,1000 μg/g, or equimolar with nitrite level) and polyphosphate (Curaphos 700; 0, 0.3% w/v), on the growth of Clostridium botulinum types A and B was studied in an experimental pork slurry system, without heating and after two heat treatments (80°C for 7 min and 80°C for 7 min plus 70°C for 1 hr) followed by storage at: 15, 17.5, 20 or 35°C for up to 6 months.
Statistical analyses showed that increasing salt or nitrite levels, adding isoascorbate or nitrate, using the highest heat treatment or decreasing the storage temperature all significantly reduced toxin production by Cl. botulinum . The addition of 0.3% polyphosphate (Curaphos 700) significantly increased toxin production. There were many significant two-factor interactions; the effect of increasing nitrite was relatively less if isoascorbate was present, at 4.5% salt, or at low storage temperature. The presence of isoascorbate also counteracted the increase in toxin production attributed to the presence of polyphosphate.     

Influence of sodium pyrophosphate on thermal inactivation of Listeria monocytogenes in pork slurry and ground pork

The thermal inactivation (55–62·5°C) of Listeria monocytogenes in pork slurry and ground pork that contained 0, 0·25 or 0·5% sodium pyrophosphate (SPP) was evaluated. Surviving cells were enumerated on Modified Oxford Medium. Decimal reduction (D)-values in pork slurry control (0% SPP) were 8·15, 2·57, 0·99, and 0·18 min, at 55, 57·5, 60 and 62·5°C, respectively; D-values in ground pork ranged from 15·72 min at 55°C to 0·83 min at 62·5°C. D-values in pork slurry that contained 0·25% SPP (w/v) were 4·75, 1·72, and 0·4 min, at 55, 57·5, and 60°C respectively; the values in ground pork ranged from 16·97 at 55°C to 0·80 min at 62·5°C. At 62·5°C,L. monocytogenes in slurry that contained SPP were killed too rapidly to allow determination of the D-value. Addition of 0·5% SPP further decreased (P<0·05) the heat resistance of L. monocytogenes in pork slurry but not in ground pork. The z-values in slurry ranged from 4·63 to 5·47°C whereas higher z-values (5·25 to 5·77°C) were obtained in ground pork. Degradation of SPP to orthophosphates in ground pork was two or three times greater than in pork slurry. Possible reasons for failure of SPP to reduce the thermal resistance of L. monocytogenes in ground pork are discussed.     

Factors controlling the growth of Clostridium botulinum types A and B in pasteurized cured meats IV. The effect of pig breed, cut and batch of pork

Pork slurries were prepared from leg or shoulder muscle from three animals from each of three breeds of pig (Pietrain, Gloucester Old Spot and Large White × Landrace cross). Slurries (pork:water, 1:1.5) contained NaNO₂ (100 μ/g), NaCl (2.5, 3.5 or 4.5% w/v on the water), were subjected to one of three heat treatments (unheated, 80°C for 7 min, 80°C for 7 min plus 70°C for 1 hr) and stored at 35, 20, 17.5 or 15°C for up to 6 months to determine the relative effects of the above factors on growth (spoilage) and toxin production by Clostridium botulinum types A and B at 10³ spores per bottle.
Increasing salt or heat treatment, or decreasing storage temperature or inoculum level all reduced spoilage and toxin production. Both 'animal' and 'cut' significantly affected spoilage and toxin production. More spoilage and toxin production occurred in meat from the shoulder cut than from the leg cut. In both cases there was considerable variation between animals within breed, but there was no systematic difference between breeds. There is no obvious explanation for the variation in meat between animals, but it should be borne in mind when planning and assessing results of large multifactor experiments. Although there was more spoilage and toxin production after 6 months' than 3 months' storage, the statistical analyses yielded essentially similar conclusions.     

Development of a novel milk‐based fermented product fortified with wheat germ

Wheat germ (WG) was mixed with water (1:5), heated (85 °C/15 min), cooled and used to replace 0, 20, 30 and 40% (w/w) of standardised cow's milk (3% fat), supplemented with 2%(w/w) skim milk powder. Yoghurt‐like fermented products were prepared from the different formulations, stored at 7 ± 2 °C for 15 days, and analysed for chemical composition, pH, microbiological quality, texture profile (TPA), viscosity, syneresis and sensory properties. The addition of WG slurry enhanced acid development during fermentation and increased the viscosity of the fermented products. Nutritious milk‐based fermented products of acceptable composition and quality could be prepared from formulations containing 20% (w/w) WG slurry.     

Ohmic Cooking of Processed Meats and its Effects on Product Quality

ABSTRACT: A basic bologna emulsion (lean and fatty pork meat, sodium chloride, sodium erythorbate, and sodium nitrite) was cooked in 1-kg portions, either in a smokehouse (180-min cycle; to 70 °C at core) or by ohmic heating (64 to 103 V; 3.9 °C/min to 10.3 °C/min; to 70 °C to 80 °C), and the finished products were compared for color, texture, pH, drip, Eh, and rancidity. Heating rates, final temperatures, and a 20-min holding time had little influence on the quality of ohmic sausages. In addition, ohmic sausages were always found to be similar to smokehouse products except for texture, which was significantly softer (P > 0.05) in ohmic products but could be hardened by use of binders.     

Response surface methodology for protein extraction optimization of red pepper seed (Capsicum frutescens)

Response surface methodology was used to determine optimum conditions for extraction of protein from red pepper seed meal. A central composite design including independent variables such as temperature (30, 35, 40, 45 and 50 °C), pH (7.0, 7.5, 8.0, 8.5 and 9.0), extraction time (20, 30, 40, 50 and 60 min) and solvent/meal ratio (10:1, 15:1, 20:1, 25:1 and 30:1 v/w) was used. Selected response (dependent variable) which evaluates the extraction process was protein yield and the second-order model obtained for protein yield revealed coefficient of determination of 96.7%. Protein yield was primarily affected by pH and solvent/meal ratio. Maximum yield was obtained when temperature, pH, mixing time and solvent/meal ratio were 31 °C, 8.8, 20 min, 21:1 (v/w), respectively. These conditions resulted in protein yield of 12.24 g of soluble protein from extract/100 g defatted red pepper seed flour. The adequacy of the model was confirmed by extracting the protein under optimum values given by the model. These results help in designing the process of optimal protein extraction from red pepper seeds.     

Effect of extraction conditions on lycopene extractions from tomato processing waste skin using response surface methodology

Skin, rich in lycopene, is an important component of waste originating from tomato paste manufacturing plants. A central composite design with five independent variables, namely solvent/meal ratio (20:1, 30:1, 40:1, 50:1, and 60:1 v/w); number of extractions (1, 2, 3, 4 and 5); temperature (20, 30, 40, 50 and 60 °C); particle size (0.05, 0.15, 0.25, 0.35 and 0.43 mm); extraction time (4, 8, 12, 16 and 20 min) was used to study their effects on lycopene extraction. The experimental values of lycopene ranged between 0.639 and 1.98 mg/100 g. The second order model obtained for extracted lycopene revealed a coefficient of determination (R²) of 0.99 and a standard error of 0.03. Maximum lycopene (1.98 mg/100 g) was extracted when the solvent/meal ratio, number of extractions, temperature, particle size and extraction time were 30:1 v/w, 4, 50 °C, 0.15 mm and 8 min, respectively.     

Use of Candida tropicalis ATCC 9968 to Adjust the pH of a Natural Lactic Acid Fermentation of Cornmeal

After 3 days of a natural lactic acid fermentation of whole kernel cornmeal, the pH was 3.78 with a titratable acidity of 0.91% at 32°C (1:4 w/v solids to water). These solids were diluted (1:12 w/v), autocalved at 121°C for 15 min and fermented with C. tropicalis for 7 days at 32°C, bringing the pH to 6.5 and 0.03% acidity. After both fermentations, the % relative nutritive value increased significantly (from 74.09% to 81.22%) and so did riboflavin (from 0.22 to 0.56 mg/100g). Both thiamin and niacin decreased significantly (0.42 to 0.20 mg/100g and 2.13 to 1.94 mg/100g, respectively).     

PREDICTIVE MODEL FOR THE COMBINED EFFECT OF TEMPERATURE,pH, SODIUM CHLORIDE,AND SODIUM PYROPHOSPHATE ON THE HEAT RESISTANCE OF ESCHERICHIA COLI O157:H71

The effects and interactions of heating temperature (5–62.5C), pH (4 – 8), NaCl (0 – 6%, w/v), and sodium pyrophosphate (0 – 0.3%, w/v) on the heat resistance of a four strain mixture of Escherichia coli O157:H7 in beef gravy were examined. Thermal death times were determined using a submerged coil heating apparatus. The recovery medium was plate count agar supplemented with 1% sodium pyruvate. Decimal reduction times (D-values) were calculated by fitting a survival model to the data with a curve fitting program. The D-values were analyzed by second order response surface regression for temperature, pH, NaCl and sodium pyrophosphate levels. The four variables interacted to affect the inactivation of the pathogen. Thermal resistance of E. coli O157:H7 can be lowered by combining these intrinsic factors. A mathematical model describing the combined effect of temperature, pH, NaCl and sodium pyrophosphate levels on the thermal inactivation of E. coli O157:H7 was developed. The model can predict D-values for any combinations of temperature, pH, NaCl and sodium pyrophosphate that are within the range of those tested.     

Effect of food characteristics, storage conditions, and electron beam irradiation on active agent release from polyamide-coated LDPE films

ABSTRACT:  We investigated the effect of electron beam irradiation, storage conditions, and model food pH on the release characteristics of trans -cinnamaldehyde incorporated into polyamide-coated low-density polyethylene (LDPE) films. Active agent release rate on irradiated films (up to 20.0 kGy) decreased by 69% compared with the nonirradiated controls, from 0.252 to 0.086 μg/mL/h. Storage temperature (4, 21, and 35 °C) and pH (4, 7, and 10) of the food simulant solutions (10% aqueous ethanol) affected the release rate of trans -cinnamaldehyde. As expected, antimicrobial release rate decreased to 0.013 μg/mL/h at the refrigerated temperature (4 °C) compared to the higher temperatures (0.029 and 0.035 μg/mL/h at 21 and 35 °C). The fastest release rate occurred when exposed to the acidic food simulant solution (pH 4). In aqueous solution, trans -cinnamaldehyde was highly unstable to ionizing radiation, with loss in concentration from 24.50 to 1.36 μg/mL after exposure to 2.0 kGy. Fourier transform infrared (FTIR) analysis revealed that exposure to ionizing radiation up to 10.0 kGy did not affect the structural conformation of LDPE/polyamide films and the trans -cinnamaldehyde in the films, though it induced changes in the functional group of trans -cinnamaldehyde when dose increased up to 20.0 kGy. Studies with a radiation-stable compound (naphthalene) showed that ionizing radiation induced the crosslinking in polymer networks of LDPE/polyamide film and caused slow and gradual release of the compound. This study demonstrated that irradiation serves as a controlling factor for release of active compounds, with potential applications in the development of antimicrobial packaging systems.     

pH Induced Aggregation and Weak Gel Formation of Whey Protein Polymers

Whey protein polymers were formed by heating (80 °C) a 4% (w/v) whey protein (WP) isolate dispersion at pH 8.0 for 15, 25, 35, 45, or 53 min. Dispersions were adjusted to pH 6.0, 6.5, 7.0, 7.5, or 8.0 after heating and the rheological properties were determined. Viscosity increased with increased heating time and decreased pH. At pH 7.0 and 7.5, high-viscosity dispersions with pseudoplastic and thixotropic flow behavior were formed, while weak gels were formed at pH 6.0 and 6.5. The storage (elastic) and loss (viscous) moduli of pH-induced gels increased when temperature was increased from 7 °C to 25 °C, suggesting that hydrophobic forces are responsible for gelation. Key Words: weak-gels, whey proteins, polymers, gelation, functionality     

Determination of Spiramycin and Josamycin in Milk By HPLC and Fluorescence Detection

ABSTRACT: A reversed-phase high-performance liquid chromatographic (HPLC) method is described for the simultaneous determination of spiramycin and josamycin in milk. The extract obtained from milk, using liquid-liquid extraction, was treated with cyclohexa-1,3-dione in ammonium acetate buffer (pH 7.0) for 60 min at 90°C. The derivative was chromatographed on an octadecylsilane (ODS) column at 45°C. Separation was performed by using a mobile phase consisting of an acetonitrile-methanol-phosphate buffer (pH 6.0) mixture. Fluorescence detection was achieved at 375 nm for the excitation wavelength and 450 nm for the emission wavelength. Linearity was demonstrated between 50 and 500 μg/L. Recoveries were about 90% and the detection limits were 8 and 13 μg/L for spiramycin and josamycin, respectively.     

Rheology and Oxidative Stability of Whey Protein Isolate-Stabilized Menhaden Oil-in-Water Emulsions as a Function of Heat Treatment

ABSTRACT:  Menhaden oil-in-water emulsions (20%, v/v) were stabilized by 2 wt% whey protein isolate (WPI) with 0.2 wt% xanthan gum (XG) in the presence of 10 mM CaCl₂ and 200 μM EDTA at pH 7. Droplet size, lipid oxidation, and rheological properties of the emulsions were investigated as a function of heating temperature and time. During heating, droplet size reached a maximum at 70 °C and then decreased at 90 °C, which can be attributed to both heating effect on increased hydrophobic attractions and the influence of CaCl₂ on decreased electrostatic repulsions. Combination of effects of EDTA and heat treatment contributed to oxidative stability of the heated emulsions. The rheological data indicate that the WPI/XG-stabilized emulsions undergo a state transition from being viscous like to an elastic like upon substantial thermal treatment. Heating below 70 °C or for less than 10 min at 70 °C favors droplet aggregation while heating at 90 °C or for 15 min or longer at 70 °C facilitates WPI adsorption and rearrangement. WPI adsorption leads to the formation of protein network around the droplet surface, which promotes oxidative stability of menhaden oil. Heating also aggravates thermodynamic incompatibility between XG and WPI, which contributes to droplet aggregation and the accumulation of more WPI around the droplet surfaces as well.     

Enzymatic Production of Ribonucleotides from Autolysates of Kluyveromyces marxianus Grown on Whey

After 20h fermentation of medium containing 5% (w/v) dehydrated whey, at 30°C, pH 4.5, yeast cells were harvested, diluted in 0.1M KH₂PO₄, and autolyzed at different pHs (6.5–7.5) and temperatures (45–55°C). Phosphodiesterase (0.2–1.0% w/v, 65°C, pH 6.5, 6h) and adenyl deaminase (0.5-1.0% w/v, 60°C, pH 5.5, 4h) were added to the autolysates. After heat treatment (100°C, 15 min), samples were analyzed by RP-HPLC and LC/MS. Production of 5′-ribonucleotides was maximized at 50°C, pH 6.5. Yields of 5′-AMP (800 μg/g of biomass) and 5′-GMP (2000 μg/g) increased considerably after addition of 1.0% phosphodiesterase. 5′-IMP increased only after addition of 1.0% adenyl deaminase.     

Control of a range of food related microorganisms by a multi-parameter preservation system

Seventy-two process variables, based on a matrix of a _w nature of controlling solute, pH, and the addition of sodium citrate and sodium benzoate were examined with a view t o devising a food preservation system for ambient temperatures. Growth of a challenge'cocktail' of Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Streptococcus faecalis, Lactobacillus casei and Clostridiurn perfringens, was assessed in a Brain Heart Infusion broth based model system. Each of the controlling factors had an effect on growth. The addition of sodium citrate (2% w /v) and sodium benzoate (2000 mg/I) enhanced the inhibitory effect. Reduction in a _w (1.00–0.94) and pH (7.0–5.5) in combination or as separate controlling factors increased any inhibition. Combinations of sodium chloride and glycerol were used as the controlling solute, and increasing the proportion of sodium chloride resulted in suppressed growth, irrespective of any change in a _w or pH. Combinations of sodium citrate and sodium benzoate with a pH less than 6.0 and an a, less than 0.95 inhibited any growth during a 42 day incubation period at 37°C, irrespective of the controlling solutes studied.     

Formulation and shelf-life of a bottled pawpaw juice beverage

A simple procedure was developed for production of bottled pawpaw beverage juice by peeling and macerating peeled tissue in 25% water, straining through a 0.8-mm sieve, adjustment of juice pH with citric acid and flavour adjustment with sucrose. Fresh juice was optimized for acceptability at pH 3.9 and 10% (w/w) sucrose. Heating for 6 min at 72.2°C was required to achieve commercial pasteurization. Samples of juice were prepared with no preservative, and containing sodium benzoate (125mg/100ml), sodium metabisulphite (50mg/100ml) and sodium metabisulphite/sodium benzoate combination (25mg and 60mg/100ml) for trials in which acceptability, pH, specific gravity, brix, total acidity, vitamin C and biomass concentrations were measured over 90 weeks storage at 10°C and 30.2°C. Sodium benzoate alone extended the shelf-life at 30°C up to 80 weeks but the other preservatives were not effective after 20 weeks. The control juice was already deteriorating by 10 weeks at 30°C. At 10°C all preserved samples were stable up to 80 weeks, although the control deteriorated rapidly after 20 weeks.     

Sodium Lactate/Sodium Chloride Effects on Aerobic Plate Counts and Color of Aerobically Packaged Ground Pork

Ground pork (15% fat) was formulated to contain 0% to 3.0% sodium chloride and/or 0% to 3.0% sodium lactate (SL) resulting in 28 treatment combinations. Five replications consisted of two with low initial microbial loads (< 10³ CFU/g) and three with high initial loads (> 10⁵ CFU/ g). Ground pork (454g) was overwrapped in PVC and stored (4°C) aerobically for 21 d. A significant salt × SL interaction existed for redness of samples with low initial aerobic plate count (APC). Red color was best preserved by 2.0% or 3.0% SL. Initial pH values of low and high initial APC samples were similar. Initial product pH was best maintained by higher SL levels in low initial load samples and by higher sodium chloride levels in high initial load samples. Samples containing 3.0% SL had the lowest APC regardless of salt level.     

Carotenoids production from a newly isolated <Emphasis Type="Italic">Sporidiobolus pararoseus</Emphasis> strain by submerged fermentation

This work aimed at evaluating the total carotenoids production by a newly isolated Sporidiobolus pararoseus. Bioproduction was carried out in an orbital shaker, using 10% (w/v) of inoculum (25 °C, 180 rpm for 35 h), incubated for 120 h in a dark room. Liquid N₂ and dimethylsulphoxide (DMSO) were used for cell rupture, and carotenoids were extracted with a solution of acetone/methanol (7:3, v/v). Optimization of carotenoids bioproduction was achieved by experimental design technique. Initially, a Plackett–Burman design was used for the screening of the most important factors, after the statistical analysis, a complete second-order design was carried out to optimize the concentration of total carotenoids in a conventional medium. Maximum concentration of 856 μg/L of total carotenoids was obtained in a medium containing 60 g/L of glucose, 15 g/L of peptone, and 15 g/L of malt extract, 25 °C, initial pH 4.0 and 180 rpm. Fermentation kinetics showed that the maximum concentration of total carotenoids was reached after 102 h of fermentation and that carotenoids bioproduction was associated with cell growth.     

Extraction optimization of watermelon seed protein using response surface methodology

Extraction conditions for maximum protein recovery from watermelon (Citrullus vulgaris Cv Sugar baby) seed meal were investigated using response surface methodology. A central composite design with four independent variables: temperature (40, 45, 50, 55 and 60 °C); NaOH concentration (0.03, 0.06, 0.09, 0.12 and 0.15 g/L); extraction time (5, 10, 15, 20 and 25 min) and solvent/meal ratio (30:1, 40:1, 50:1, 60:1 and 70:1, v/w) was used to study the response variable (protein yield). The experimental values of protein yield ranged between 72.03 and 81.52 g/100 g seed meal. A second-degree equation for independent and response variables was computed and used to create the contour plots graphs. The predicted values obtained for protein yield revealed that coefficient of determination and standard error was 0.80 and 0.906, respectively. Optimum protein extraction was obtained with 0.12 g/L alkali concentration, 15 min extraction time and 70:1 (v/w) solvent/meal ratio at 50 °C. Confirmatory studies revealed that the protein yield under optimum conditions was 80.71 g/100 g seed meal.