Antigenicity of Ovomucoid Remaining in Boiled Shell Eggs

Antigenicity of egg white proteins which remained in heated shell eggs was analyzed quantitatively by using rabbit antibodies specific to egg white proteins and human antibody from patients allergic to egg. The major antigenic component in heated (100°C for 20 min) and coagulated egg white was ovomucoid. A considerable amount of ovomucoid remained immunoreactive even after heating at 100°C for 15 min, though ovomucoid in stored eggs was a little less stable to heating than that of fresh eggs. Even long-time heating (100°C for 45 min) could not completely eliminate the ovomucoid immunoreactivity to human IgE antibody.     

Control of the bacteriological condition of calf brain. II. The effects of lactic acid decontamination and frozen storage

In two experiments the effects of lactic acid decontamination (LAD) and frozen storage on the bacteriological condition of calf brain were investigated. The first experiment incuded 80 calves, whose brains were extracted manually after splitting of the occipital bone with an axe. Upon removal, 40 brains were sprayed with 1.25% (v/v) L-lactic acid, whereas 40 brains remained untreated. At day 1 cone-shaped samples of 10 g were excised from 20 brains of each group at undamaged sites of the hemispheres and at the sites of impact of the captive bolt. After 7 days of storage at 3 ± 1°C in polystyrene trays the 20 remaining brains were sampled. The bacteriological examination included aerobic colony count at 30°C (ACC-30) and 4°C (ACC-4), mesophilic Enterobacteriaceae colony count (EC-37) and Lancefield group D streptococci colony count. For both locations and with regard to all parameters examined LAD resulted in significantly lower bacterial counts at day 1 as compared with controls. However, the differences were slight particularly at the damaged locations where a reduction in ACC-30 and ACC-4 of only 0.3 log g^?1 was effected. At day 8, bacterial counts were no longer significantly different, with the exception of ACC-4 at the site of impact of the captive bolt, which was 7.0 log g^?1 and 7.5 log g^?1 for treated and control brain respectively. Moreover, treated brain exhibited an unacceptable discolouration. From these findings it was concluded that lactic acid decontamination does not give an appreciable extension of the storage life of calf brain. The second experiment involved aseptically removed brains of 20 mechanically stunned calves. Ten brains were sampled at day 1, whereas brains of 10 other calves were stored at ?40°C for 7 days. Subsequent they were allowed to thaw for 1 day at 3 ± 1°C. At day 9 these brains had bacterial counts similar to those obtained at day 1. Thawing loss was somewhat higher (5.1%) than the weight loss of cooler-stored controls stored at 3 ± 1°C (1.2%). It is concluded that in view of the susceptibility of calf brain to bacterial spoilage, freezing should be taken into consideration as an effective means to prevent growth of bacteria that will lead to deterioration.     

Effect of heating,pH and thermoradiation on inactivation of Vibrio vulnificus

The effects of heating, thermoradiation and pH (5·5 to 7·0) on inactivation of V. vulnificus cells in buffers, oyster and fish homogenates were studied. Cells were more sensitive to thermoradiation than heating or radiation alone. Synergistic effects were observed during thermoradiation of V. vulnificus (10⁷ cells ml^-1) at 40°C in buffer (pH 5·5), in fresh oyster (pH 6·2) and in fresh fish (pH 6·7). This synergistic effect was also noted when the same number of cells in fresh fish homogenates were irradiated at 45°C. Inactivation of cells varied depending on the environment and were more pronounced in buffers than in oyster or fish homogenates. The D₁₀ (dose in kGy inactivating 90% of cells) at 25·C was 0·078 in buffer (pH 7·0), 0·125 in oyster (pH 6·2) and 0·187 in fish (pH 6·7), but at 35°C, the D₁₀ values were 0·054, 0·093 and 0·125 kGy, respectively. Low initial numbers of cells (10 ml^-1) in pH 7·0 buffer were rapidly inactivated by thermoradiation (40·C) compared to high cell number (10⁷ ml^-1) and the D₁₀ (kGy) was 0·024 for the former and 0·047 latter. These D₁₀ values (kGy) were 0·046 and 0·093 in fresh oysters (pH 6·2), 0·093 and 0·109 kGy in fresh fish (pH 6·7), for the low and the high cell numbers, respectively following thermoradiation at 40°C.     

Behaviour of Listeria monocytogenes and Staphylococcus aureus in sliced,vacuum-packaged raw milk cheese stored at two different temperatures and time periods

The behaviour of Listeria monocytogenes and Staphylococcus aureus in raw milk cheese slices packaged under vacuum was evaluated. Artificially contaminated 80-day ripened cheese was portioned, vacuum packaged, and then stored for 28 days at 4 °C and for 56 days at 10 °C. Bacterial counts were obtained before vacuum packaging and then weekly during storage. At the end of ripening, the initial L. monocytogenes count was 4.46 ± 0.89 log cfu g⁻¹; weekly bacterial counts remained substantially unchanged in the samples stored at 4 °C but decreased to 3.54 ± 1.54 log cfu g⁻¹ in those stored at 10 °C. The initial S. aureus count before vacuum packaging was 3.60 ± 0.78 log cfu g⁻¹; it then gradually decreased to 2.60 ± 1.32 log cfu g⁻¹ in the samples stored at 4 °C and to about 1.9 log cfu g⁻¹ in those stored at 10 °C.     

Influence of storage temperature on the quality of salted mackerel (Rastrelliger kangurta) and pink perch (Nemipterus japonicus)

Dry-salted mackerel and pink perch were stored at two temperatures: ambient (26·8 ± 3·3°C) and 2·5 ± 1°C. Changes in moisture content, salt content, water activity (a_w), peroxide value (PV), free fatty acid content (FFA), total volatile base nitrogen (TVBN) content, halophilic bacterial count and sensory scores for overall acceptability were studied. Loss of moisture and absorption of salt were considerably higher in the products stored at ambient temperature. The decrease in a_w was more pronounced at ambient temperature than at the lower temperature. Although the chemical indices of freshness (PV, FFA and TVBN) and the halophilic counts showed increasing trends, they were considerably lower in the products stored at the lower temperature. Sensory evaluation for overall acceptability indicated that storage at the lower temperature could considerably extend the shelf-life of salted fish.     

Effect of frozen storage on thermal stability of sarcoplasmic protein and myofibrillar protein from common carp (Cyprinus carpio) muscle

Thermal stability of sarcoplasmic protein and myofibrillar protein extracted from fresh and frozen common carp was comparatively studied. Total sulphydryl content (SH) in sarcoplasmic protein solution from 5‐month frozen carp decreased by 19.43% compared with fresh sample. The SDS‐PAGE patterns showed that all the bands of sarcoplasmic protein from frozen‐stored samples were almost invisible at 80 °C. Myofibrillar protein from fresh sample exhibited lower turbidity and surface hydrophobicity and higher Ca²⁺‐ATPase activity and SH content than frozen‐stored sample when heated from 20 to 80 °C. The Ca²⁺‐ATPase activity from fresh (M0), 2 (M2)‐ and 5 (M5)‐month frozen‐stored carp was completely lost at 48, 46 and 46 °C, respectively. When heated to 80 °C, the SH content of myofibrillar solutions in M0, M2 and M5 decreased by 26%, 60% and 70%, respectively. Sarcoplasmic and myofibrillar proteins from frozen carp were more susceptible to aggregate during heating treatment.     

Vibrio parahaemolyticus in granulated ark shell clam (Tegillarca granosas): accumulation from water and survival during cold storage and thermal process

This study investigated accumulation of Vibrio parahaemolyticus in granulated ark shell clam (Tegillarca granosas) exposed to contaminated water and survival of V. parahaemolyticus in the clams during cold storage and heating processes. Vibrio parahaemolyticus could be accumulated in clams to a level similar to that of contaminated water within 12 h of exposure of clams to contaminated water at temperatures between 9 and 33 °C. Keeping clams stored at 5 and 0 °C for 10 days resulted in 1.98 and 2.32 log MPN g^?1 reductions of V. parahaemolyticus, respectively, in the clams. Frozen storage at ?18 °C for 15 days or at ?30 °C for 30 days were capable of reducing V. parahaemolyticus from 4.05 log MPN g^?1 to non‐detectable levels (< 3 MPN g^?1). A heating process in hot water at 80 °C or higher for 1 min also reduced V. parahaemolyticus in the clams to non‐detectable levels.     

The fate of Escherichia coli O157 : H7 in Myzithra,Anthotyros, and Manouri whey cheeses during storage at 2 and 12°C

Myzithra, Anthotyros and Manouri whey cheeses were inoculated the day after production withEscherichia coli O157 : H7 at concentrations of approx. 1·8×10⁶cfu g⁻¹, and stored at 2 and 12°C for 30 and 20 days, respectively. The pH of the whey cheeses decreased from an initial value of approx. 6·20 to 5·83 or 5·60 (Myzithra) 5·75 or 5·20 (Anthotyros) and 5·80 or 5·30 (Manouri) by the end of the corresponding storage periods at 2 and 12°C, respectively. Escherichia coli O157 : H7 populations in the whey cheeses at the end of the 12°C storage period, had grown with an increase of approx. 1·3 log₁₀cfu g⁻¹. E. coli O157 : H7 populations in whey cheeses at the end of the 2°C storage period did not grow and decreased, with an approx. 2·5 log₁₀cfu g⁻¹reduction. Results showed that E. coli O157 : H7 can grow at 12°C and survive at 2°C storage in Myzithra, Anthotyros and Manouri whey cheeses, and therefore post-manufacturing contamination with this pathogen must be avoided by employing hygienic control programmes such as HACCP.     

Spore-forming bacteria in commercial cooked,pasteurised and chilled vegetable purées

In commercial purées of broccoli, carrot, courgette, leek, potato and split pea, pasteurized in their final packaging and analysed at two periods, Bacillus spp. were the dominant aerobic mesophilic bacteria (AMB). Initial numbers were generally lower than 2 log cfu g⁻¹. They increased up to 6–8 log cfu g⁻¹after about 20 days of storage at 10°C. At 4°C, numbers of AMB after 20 days were lower than 3 log cfu g⁻¹in potato purée, lower than 4 log cfu g⁻¹in leek purée, and between 3 and 6 log cfu g⁻¹in other products. Strict anaerobes were in markedly lower numbers than AMB. At all storage temperatures tested courgette purée usually showed the most rapid bacterial growth and spoilage. On this product, an increase in storage temperature from 4°C to 10°C resulted in a threefold reduction in time to 5 log cfu g⁻¹, and time to spoilage. Growth kinetics of AMB in courgette purée at 20°C, 15°C, 10°C, 6·5°C and 4°C were determined using a mathematical model. Three hundred and forty eight isolates were identified using the API system. Bacillus circulans, B. macerans and B. polymyxa were among the main species isolated from products stored at 4°C and 10°C, while B. subtilis and B. licheniformis were the dominant species in product stored at abuse temperature. Bacillus cereus was isolated from all storage conditions, but mostly from products stored at abuse temperature.     

Optimization of Headspace Single-Drop Microextraction Coupled with Gas Chromatography–Mass Spectrometry for Determining Volatile Oxidation Compounds in Mayonnaise by Response Surface Methodology

In this assay, headspace single-drop microextraction (HS-SDME) coupled with gas chromatography–mass spectrometry (GC–MS) as a simple, low-cost and rapid method has been developed and validated for determining volatile oxidation compounds including hexanal and heptanal in mayonnaise. The main microextraction variables affecting the HS-SDME procedure such as extraction temperature and time, stirring rate, and amount of NaCl were optimized by response surface methodology employing a central composite design. Obtained results demonstrated that higher yield of extracted analytes could be achieved under the following optimal conditions: extraction temperature of 45 °C, extraction time of 16 min, stirring rate at 700 rpm, and addition of 2 g NaCl. The optimized HS-SDME/GC–MS method was validated for oxidized mayonnaise samples (50 °C/48 h) by calculating analytical parameters (linearity, precision, accuracy, and sensitivity). Good linearity (R ²?>?0.99) was observed by plotting calibration curves of extracted hexanal and heptanal over the concentration range of 0.025–10 μg g^?1, and the repeatability of the method, expressed as relative standard deviation, were found to be 4.04 % for hexanal and 3.68 % for heptanal (n?=?7). After the microextraction process of spiked mayonnaise sample, high levels of relative recovery were obtained for hexanal (107.33 %) and heptanal (91.43 %). The detection limits were 0.008 ng g^?1 and 0.021 ng g^?1 for hexanal and heptanal, respectively, while quantification limits of hexanal and heptanal were calculated to be 0.027 ng g^?1 and 0.071 ng g^?1, respectively. The possibility of the HS-SDME followed GC–MS to determine and quantify volatile oxidation compounds such as hexanal and heptanal was confirmed by analyzing commercial fresh mayonnaise stored at 4 and 25 °C during 3 months.     

The effect of temperature abuse on Clostridium perfringens in cooked turkey stored under air and vacuum

The potential for growth of Clostridium perfringens in aerobic and anaerobic (vacuum) packaged cooked ground turkey was investigated. Samples of autoclaved ground turkey were inoculated with ∼3·0 log₁₀ cfu g^-1 of C. perfringens strain NCTC 8238 or NCTC 8239, packaged and stored at various temperatures. Vegetative growth and heat-resistant spores were enumerated by plating unheated and heated (75°C for 20 min) samples, respectively, on tryptose-sulfite-cycloserine agar. The type of atmosphere influenced the growth of C. perfringens at 15 and 28°C. Both strains grew to about 7 logs within 9 h anaerobically and by 24 h aerobically at 28°C. While aerobic growth was slow at 15°C, mean log₁₀ cfu g^-1 increased anaerobically by 4-4·5 logs by day 8 for both strains. Spores were not found at 4 and 15°C, but were detected as early as 24 h at 2°C under anaerobic conditions in both strains. C. perfringens population stabilized or slowly decreased at 4°C. Cyclic and static temperature abuse of refrigerated products for 5 h will not permit C. perfringens growth. However, temperature abuse of such products for relatively long periods may lead to high and dangerous numbers of organisms. Reheating such products to an internal temperature of 65°C before consumption would prevent food-poisoning since the vegetative cells were killed.     

Volatile amine production in uncured pork during storage

The concentration of volatile amines and the bacterial counts were determined in pork meat stored at ?20, +5 and +20 °C. Amine formation appeared to be independent of bacterial growth until the count reached 10⁹/cm². The meat spoiled before the dimethylamine/trimethylamine content reached a concentration likely to yield a detectable amount of N-nitrosodimethylamine in a cured product.     

Effect of temperature and bulk density on thermal conductivity of spray-dried whole milk powder

The thermal conductivity of whole milk powder was determined by a steady-state guarded hot-plate method at temperatures ranging from 11·8 to 43·2°C, at bulk densities 0·512 and 0·605 g cm^?3.It was found that thermal conductivity increased with increasing temperature and with increasing bulk density. Thermal conductivity increased from 0·036 W m^?1 K^?1 at 11·8°C to 0·077 W m^?1 K^?1 at 43·2°C for bulk density 0·512 g cm^?3, while for bulk density 0·605 g cm^?3 thermal conductivity increased from 0·058 W m^?1 K^?1 at 16·6°C to 0·093 W m^?1 K^?1 at 42·8°C.     

Quality and hygiene of beef burgers in relation to the addition of sodium ascorbate,sodium citrate and sodium acetate

We evaluated the effects of two additive mixtures (sodium ascorbate 1 g kg^?1, sodium citrate 1 g kg^?1 and sodium acetate 1.75 or 2.5 g kg^?1) on the microbiological and physical–chemical characteristics of non‐prepacked beef burgers stored in air at 4 °C or 12 °C for 96 h. Total microbial count reached 7 Log CFU g^?1 48 h later in treated samples at 4 °C. The mixture containing the higher acetate concentration led to a smaller increase in Gram‐negatives, in particular Pseudomonas (2 Log of difference towards control samples at 96 h); at 12 °C, a 1.7 Log difference in Enterobacteriaceae was also shown. Total viable basic nitrogen was significantly lower in the treated samples at 12 °C. The addition resulted in pH stabilisation and lower cooking loss and positively influenced the a* index of burgers at 4 °C. Clearly, the use of these mixtures should not be a substitute of good hygienic practices and optimal storage conditions.     

Effect of Storage Conditions on the Quality Attributes of Shell (Table) Eggs

In tropical countries like Nigeria, egg preservation is a serious problem. The common practice is to store under ambient condition due to lack of refrigeration facilities and erratic power supply. Four crates of fresh table eggs were bought from the University of Agriculture, Makurdi farm and preliminary investigations of egg weights, Haugh unit, pH and yolk index were carried out before storage and found to be within standard. Thirty eggs were stored under ambient condition with and without application of oil respectively. The other group of thirty eggs was refrigerated. The initial weights were in the range of 60 – 69 g which reduced drastically. All other quality indices like the Haugh unit, the yolk index and pH declined drastically within the four weeks of the storage especially those that were stored under the ambient conditions. Those stored under refrigeration and those that were oiled and stored under ambient conditions (32 + 2 °C) maintained high quality standards in all the quality indices evaluated. The microbiological result also showed higher bacteria, yeast and mould count on those stored under ambient condition with the initial count of 5.0 × 10³ at first week and 2.8 × 10⁷ at the fourth week while the oiled and refrigerated eggs had values of 5.0 × 10³ at week zero and 7.2 × 10⁴ at week four of storage respectively. It is suggested that application of oil on eggs before storage can be practised to ensure retention of good quality eggs especially in the tropics and most developing nations of the world.     

Variety and storage conditions affect the precursor content and amount of acrylamide in potato crisps

BACKGROUND: Acrylamide, a probable human carcinogen, is formed from the amino acid asparagine and reducing sugars when potato products are processed at high temperatures. This is a two‐year study on five Swedish‐grown potato clones, two of which are adapted to cold storage. The clones represented a wide range of precursor concentrations: asparagine, 3.7–15.3 mg g^?1; reducing sugars, 0.9–14.9 mg g^?1. Crisps were prepared in laboratory‐scale equipment mimicking industrial processing conditions. RESULTS: Potatoes stored at 4 °C had significantly higher levels of glucose and fructose than potatoes stored at 8 °C. Acrylamide levels were significantly higher in crisps made from potatoes stored at 4 °C. Two clones with a large difference in asparagine concentration but similar glucose and fructose concentrations gave crisps with significantly different acrylamide contents. The lowest levels of acrylamide were found in crisps made from the potato variety with the lowest asparagine concentration. CONCLUSION: The findings show that variety and storage conditions influence the levels of precursors. Acrylamide formation in crisps can be reduced by using potato varieties with low levels of both asparagine and reducing sugars. Mass transport of precursors during heating is suggested to be important for acrylamide formation in potato crisps. Copyright © 2007 Society of Chemical Industry     

The effect of storage on the oxalate content of New Zealand grown oca

Four lines of oca, No. 38 and 41, Inca Gold and Market were grown in four replicated plots and the soluble oxalate content was determined on the freshly harvested tubers and tubers that had been stored for 6 weeks at 16.4 ± 0.5 °C. The mean dry matter content of freshly harvested tubers was 14.3 ± 0.5 g 100 g^?1 fresh weight (FW), and after storage was 14.6 ± 0.5 g 100 g^?1 FW. The mean soluble oxalate content of freshly harvested tubers was 162.1 ± 8.8 mg 100 g^?1 FW, and, after 6 weeks storage, 173.5 ± 0.9 mg 100 g^?1 FW. The different cultivars behaved differently during storage, the soluble oxalate content of Inca Gold tubers fell 7.2% while the soluble oxalate content of the other three cultivars increased (mean 13%).     

Microbiological and biochemical quality of grouper (Epinephelus chlorostigma) stored in dry ice and water ice

The changes in the microbiological and biochemical quality of grouper (Epinephelus chlorostigma) stored in dry ice (solid carbon dioxide) were investigated. Fresh fish stored in dry ice at the ratio of 1:1 (wt/wt) were found to be organoleptically suitable for consumption when they were stored for 30 h without re‐icing. Fish stored in water ice (as control) at the ratio of 1:1 (wt/wt) and in a combination of dry ice and water ice at the ratio of 1:0.2:0.5 (wt/wt/wt) were acceptable up to 18 and 24 h, respectively. Total bacterial load ranged from 10⁵ to 10⁷ CFU g^?1, while total psychrophiles from 10³ to 10⁶ CFU g^?1. Total lactics were found in the levels of 10²–10⁴ CFU g^?1. Total volatile basic nitrogen contents were within the limit of acceptability in all the three treatments, whereas trimethylamine nitrogen content exceeded the limit (15 mg%) and hypoxanthine content was 11.11 mg (100 g)^?1 on the 30 h in grouper stored only in dry ice. Lowest temperature of ?5.8 °C was recorded in grouper stored only in dry ice. Hundred percent CO₂ environment within the package was found in grouper that were stored in dry ice and combination of dry ice and water ice.     

Acid phosphatase in the tubers of Dioscorea species and its purification from the white yam (D. rotundata poir)

Acid phosphatase activity was determined in 15 cultivars from four species of yam. A 12-fold purification of the enzyme from Dioscorea rotundata (cv. chikakwondo) gave a homogeneous preparation as demonstrated by polyacrylamide gel electrophoresis. This enzyme preparation has an apparent molecular weight of 115 000 ±2000 and an optimum activity at a pH of 5·20 and a temperature of 50°C. The K_m of the enzyme is 3·81 mM with disodium p-nitrophenylphosphate (p-NNP) as a substrate. The energy of activation, heat of activation, energy of inactivation and heat of inactivation are 7·0, 6·4, 4·41 and 4·34 kcal M^?1, respectively. Although it has very little activity with most organic phosphoric acid esters, it is significantly inhibited by Ca²⁺, Hg²⁺ and EDTA and activated by Mg²⁺. The enzyme has a half-life of 50,17 or 13 days, respectively, when stored at 6-8°C, 0°C or room temperature (29±2°C).     

Quality of applesauces processed by pulsed electric fields and HTST pasteurisation†

A pilot plant scale continuous flow pulsed electric field (PEF) and high temperature short time (HTST) processing system was integrated with an aseptic packaging machine. Fuji applesauce and blueberry applesauce were processed with PEF followed by HTST pasteurisation (PEF + HTST). PEF + HTST processed Fuji applesauce from fresh Fuji apples demonstrated high and stable sensory scores during 9 months storage at 27 °C, and had comparative sensory quality with Meal Read‐to‐Eat (MRE) and commercial applesauce products stored at 4 °C. PEF + HTST processed blueberry applesauce from pre‐pasteurised materials had lower sensory scores than PEF + HTST processed Fuji applesauce and was significantly less stable during the storage at 27 °C. PEF + HTST processed applesauces had aerobic count and mould and yeast count of <10 cfu mL^?1 during storage. Electrical conductivity, pH and °Brix, were not significantly changed throughout storage time (P > 0.05).