Effect of marinating process on the microbiological quality of Pacific saury (Cololabis saira) during vacuum-packaged storage at 4 °C

This study was carried out to evaluate the microbiological quality of Pacific saury ( Cololabis saira ) treated with marinating solutions containing either 12% NaCl + 2% acetic acid or 12% NaCl + 3% acetic acid, followed by vacuum packaging and storage at 4 °C for 90 days. The fish-to-marinating-solution ratio was 1:1.5. The growth rate of aerobic, halophilic, lactic acid bacteria and Pseudomonas spp. were significantly ( P  < 0.05) reduced in marinated vs. brined (12% NaCl + 0% acetic acid) fillets. Complete inhibition in the growth of both Enterobacteriaceae and Staphylococcus aureus was detected in fillets marinated in 3% and 2% acetic acid by the days 30 and 50 of storage, respectively. Both marinating conditions resulted in shelf life extension of the product to more than 90 vs. 60 days only for the brined fillets. Listeria monocytogenes , Vibrio parahaemolyticus and Salmonella spp. could not be detected in any of the analysed raw or treated samples.     

A review of modified atmosphere packaging of fish and fishery products – significance of microbial growth, activities and safety

Modified atmosphere packaging (MAP) extends shelf-life of most fishery products by inhibiting bacterial growth and oxidative reactions. The achievable extension of shelf-life depends on species, fat content, initial microbial population, gas mixture, the ratio of gas volume to product volume, and most importantly, storage temperature. The shelf-life of fishery products is usually limited by microbial activity, although for some fatty fishes or at superchilled storage, it can be limited by nonmicrobial activity. Packaging of fishery products under modified atmospheres (MA) increases shelf-life compared with those packaged under air, but confers little or no additional shelf-life increase compared with vacuum packaging. The specific spoilage organism (SSO) of MA packaged cod at 0 °C has been found to be Photobacterium phosphoreum . Whether or not this bacterium is the general SSO for all marine temperate fishes at different storage temperatures and under various CO₂/N₂/O₂ mixtures needs to be resolved. Without proper control of storage temperature, the benefits of MAP may be lost. Higher temperatures inevitably lead to less dissolved CO₂ in the product and consequently loss of inhibitory effect, which may result in higher microbial and enzymatic activity, and uncertainties concerning the microbial safety, as food-borne pathogens might be present in the product.     

Ascorbic acid loss and sensory changes in intermediate moisture pineapple during storage at 30–40°C

Kinetics of ascorbic acid loss as a function of storage temperature (30, 35 and 40°C) and water activity of intermediate moisture pineapple slices at a _W of 0.92, 0.95 and 0.97 was modelled. Loss was faster at higher a _W but storage temperatures of 30 - 40°C had little effect at the same a _w. Colour changes were larger than flavour changes. Spoilage was only a problem at high a _w.     

Effect of Brining, Modified Atmosphere Packaging, and Superchilling on the Shelf Life of Cod (Gadus morhua) Loins

ABSTRACT:  The aim of these experiments was to evaluate the effect of brining, modified atmosphere packaging (MAP), and superchilling on the quality changes of cod loins as measured by microbial, sensory, and chemical analysis. Unbrined and brined (2.5 ± 1.0% NaCl) cod loins were kept in styrofoam boxes (air) and under modified atmosphere (MA, CO₂/O₂/N₂: 50/5/45) at 0, −2, and −3.6 °C. Samples were examined over a 4-wk period. Total viable psychrotrophic counts and counts of H₂S-producing bacteria reached higher numbers in the air-packed brined fish at −2 and −3.6 °C than in comparable unbrined groups, being significantly different ( P  < 0.05) at the lower temperature. However, lower counts of these bacteria were obtained in the brined MAP fish than in comparable unbrined fish. Counts of  Photobacterium phosphoreum  increased most rapidly in air- and MA-packed loins kept at 0 °C. Lower counts were found at superchilled temperatures. According to sensory analysis the shelf life of unbrined air-packed loins was about 11 d at 0 °C and 14 to 15 d at −2 °C. The shelf life of MA-packed unbrined loins was about 14 to 15 d at 0 °C but 21 d at −2 °C. Thus, synergism of combined superchilling (−2 °C) and MA led to a considerable shelf life increase for unbrined loins despite the fact that processing and packaging took place 4 to 5 d post-catch. The shelf life of air-packed brined loins at −2 °C was 12 to 15 d but only 13 d under MA. The same synergistic effect did therefore not apply to brined loins as with unbrined ones.     

Effect of Salt, Smoke Compound, and Temperature on the Survival of Listeria monocytogenes in Salmon during Simulated Smoking Processes

ABSTRACT:  The objectives of this study were to examine and develop a model to describe the survival of  Listeria monocytogenes  in salmon as affected by salt, smoke compound (phenol), and smoking process temperature. Cooked minced salmon containing selected levels of salt (0%, 2%, 4%, and 6%) and smoke compound (0, 5, 10, and 15 ppm phenol) were inoculated with a 6-strain mixture of  L. monocytogenes  to an inoculum level of 6.0 log₁₀ CFU/g. The populations of  L. monocytogenes  in salmon during processing at 40, 45, 50, and 55 °C that simulated cold- and hot-smoking process temperatures were determined, and the effects of salt, phenol, and temperature on the survival of  L. monocytogenes  in salmon were analyzed and described with an exponential regression. At 40 °C, the populations of  L. monocytogenes  in salmon decreased slightly with inactivation rates of <0.01 log₁₀ CFU/h, and at 45, 50, and 55 °C, the inactivation rates were 0.01 to 0.03, 0.15 to 0.30, and 2.8 to 3.5 log₁₀ CFU/h, respectively. An exponential regression model was developed and was shown to closely describe the inactivation rates of  L. monocytogenes  as affected by the individual and combined effects of salt, phenol, and smoking process temperature. Temperature was the main effector in inactivating  L. monocytogenes  while salt and phenol contributed additional inactivation effects. This study demonstrated the inactivation effects of salt, smoke compound, and temperature on  L. monocytogenes  in salmon under a smoking process. The data and model can be used by manufacturers of smoked seafood to select concentrations of salt and smoke compound and alternative smoking process temperatures at 40 to 55 °C to minimize the presence of  L. monocytogenes  in smoked seafood.     

Preservation and shelf-life extension of shrimps and clams by high hydrostatic pressure

Clam ( Venus gallina ) and shrimp ( Parapenaeus longirostris ) samples were high hydrostatic pressure (HHP) treated at 200, 220 and 250 MPa at 25, 30, 40 and 50 °C for 10 and 20 min. Based on the results of microbial reduction, the best combinations of HHP treatments were determined as 250 MPa, 50 °C, 10 min for shrimps and 220 MPa, 50 °C, 10 min for clams. HHP-treated samples stored at 25 °C (room tempertur) and 4 °C (refrigeration temperature) were analysed. According to the results evaluated, shelf-life of shrimps was found to be 12 and 16 days for storage at room and refrigeration temperatures, respectively, as compared with 4 days for non-HHP-treated samples at 4 °C. Similarly shelf-life for the clam samples was found to be 12 days for storage at room temperature and 18 days for storage at refrigeration temperature as compared with 4 days for non-HHP-treated samples at 4 °C.     

Microbiological, physicochemical and organoleptic changes in dry-salted olives of Thassos variety stored under different modified atmospheres at 4 and 20 °C

Microbiological, physico-chemical and organoleptic changes were studied in dry-salted olives, cv. Thassos, stored under different atmospheres (100% carbon dioxide and nitrogen, 40% CO₂/30%O₂/30%N₂ and air) at 4 and 20 °C for 180 days. The initial microbial flora comprised of yeasts, no lactic acid bacteria, enterobacteria, pseudomonads or Staphylococcus aureus were detected, as the low water activity/high salt content does not favour their growth. At 4 °C, the population of yeasts declined steadily throughout storage but to a different extent depending on the gaseous atmospheres. At 20 °C, there was an initial decline in yeast counts in all samples followed by a steady increase until the end of the storage period. The CO₂ atmosphere was most effective at keeping the number of yeasts low at both storage temperatures. All gas atmospheres prevented fungal growth at both temperatures apart from the samples stored in air. The pH, a_w and salt content of the olives did not change significantly throughout the storage period. The prevailing yeast species was the salt tolerant Candida famata . The organoleptic characteristics did not differ significantly among differently treated olives. However, increased rancidity and reduced fruit colour was observed in the samples stored at 20 °C.     

Microbial growth and colour of minimally processed shiitake mushroom stored at different temperatures

The effect of storage temperature on the microbiological and sensory characteristics of minimally processed shiitake was investigated. Shiitake mushrooms were washed, sanitised, packed in polystyrene trays, overwrapped with plastic film and stored at 7, 10 or 15 °C. Microbial counts, polyphenoloxidase activity, external lightness ( L* ) and acceptance tests were conducted. Mesophilic, aerobic psychrotrophic bacteria, yeasts and moulds predominated during storage. Pseudomonas was detected after 10 days' storage showing an increase of, approximately, 7 log cycles at 15 °C. Mushroom rejection occurred when the microbial population was lower than 10⁶ CFU g⁻¹, suggesting that, other factors, such as browning, affect mushroom spoilage more than microbial activity. Mushrooms treated with citric or ascorbic acids maintained high L * value during 10 days. The shelf life of minimally processed shiitake mushrooms was 10 days at 7 °C, but less than 5 days at 10 °C, and approximately 3 days at 15 °C.     

Modelling the relation between bacterial growth and storage temperature in pasteurized milks of varying hygienic quality

The shelf-life of pasteurized milk was mainly determined by the level of contamination with Gram-negative psychrotrophic bacteria. The length of lag phase of the bacteria was also important, although the generation times of the naturally contaminating flora seemed to be of little relevance except for milks where the shelf-life exceeded 10 days at 6°C. The effect of temperature on growth of the contaminants could be accurately determined by the 'square root' plot but the conceptual minimum temperature for growth (T_o) varied. The variation was related to the quality of the pasteurized milk. Effects of temperature on generation time, length of lag phase and shelf-life were most marked at temperatures below 15°C.
The microflora of pasteurized milk varied significantly with storage temperature. At refrigeration temperatures, spoilage was mainly due to the growth of Pseudomonas spp. Enterobacteriaceae and Gram-positive bacteria assumed greater importance in the spoilage of milks stored at temperatures above 10°C. Milks of good quality also contained Bacillus spp and this group of bacteria were not detectable in milks with short shelf-lives.     

Effect of temperature (0–80°C) on the interior reflectance of ovine sternomandibularis muscle

Reflectance spectra (400–800 nm) were obtained from the interior of ovine sternomandibularis muscle as temperatures changed between 0 and 80°C by means of optical fibres. Between 0 and 40°C, no significant changes were detected, but between 25 and 80°C reflectance increased (P < 0.001). The temperature coefficient of reflectance (slope/mean) reached maxima at 440 nm (0.065 °C^-1) and at 560 nm (0.039 °C^-1), but was fairly uniform for much of the remainder of the spectrum (0.028 °C^-1). Reflectance started to increase at about 35°C, and decreased between 70 and 80°C. Little evidence for the loss of red and the appearance of brown pigments was detected from estimates of chromaticity coordinates x and y. The major effect of cooking was to increase light scattering (opacity).     

Microbiological quality of sous-vide cook chill fish cakes during chilled storage (3 °C)

Fish cakes prepared from emperorbream ( Lethrinus lethrinus ) were vacuum packed (VP), conventionally cook-chilled (CCC) and sous-vide cook-chilled (SVCC) and examined for their microbiological quality and safety during chilled storage (3 °C) for a period of 3, 5 and 16 weeks, respectively, in comparison with conventional pack(CP). The shelf life of CP, VP, CCC and SVCC packs of fish cakes were 2, 2, 4 and 16 weeks, respectively, based on the acceptable break point of the overall sensory scores. The total bacterial counts were 5 log cfu g⁻¹, in CP, VP and CCC packs; and 3 log cfug⁻¹ in SVCC pack on sixteenth week. Total lactic acid bacteria were 2 log cfu g⁻¹ on 2 and 3 weeks in CP and VP, respectively. Staphylococci were detected in all packs on sixteenth week at 2 log cfu g⁻¹. Total bacilli were detected in CP and VP at 3 log cfu g⁻¹ level after 2 weeks. Aeromonads were detected after 1, 2 and 4 weeks in CP, VP and CCC packs at 3 log cfu g⁻¹. Total anaerobic sulphite-reducing clostridia were detected only in CP and CCC packs at 3 MPN counts g⁻¹ level on the final day.     

Portable Electronic Nose for Detection of Spoiling Alaska Pink Salmon (Oncorhynchus gorbuscha)

ABSTRACT:  The ability of a portable hand-held electronic nose (EN) in detecting spoilage of whole Alaska pink salmon ( Oncorhynchus gorbuscha ) stored at 14 °C and in slush ice (1 °C) was investigated. Fish were sampled daily at 14 °C for up to 3 d, while fish stored in slush ice were sampled at various intervals up to 16 d. Sensory evaluations indicated that fish were rejected at day 3 when stored at 14 °C and at day 12 when stored in slush ice. Aerobic bacteria counts for fish skin at 14 °C ranged from 3.4 log₁₀ colony-forming units (CFU)/cm² (day 0) to 4.8 log₁₀ CFU/cm² (day 3) and for fish stored in slush ice ranged from 3.4 log₁₀ CFU/cm² (day 0) to 5.5 log₁₀ CFU/cm² (day 16). The correct classification rate using forward stepwise general discriminate analysis was 85% and 92% for EN analysis of belly cavity volatiles for fish held at 14 °C and in slush ice, respectively. A predictive model may be developed for spoilage of whole Alaska pink salmon by analyzing belly cavity odors using the EN.     

THERMAL CONDUCTIVITY OF CHICKEN MEAT AT TEMPERATURES BETWEEN −75 AND 20°C

Effects of temperature and time postmortem on the thermal conductivity of white and dark chicken meat were studied using a line heat source thermal conductivity probe to measure thermal conductivity. The effect of time postmortem was determined at body temperature and 20° C by leaving probes in whole birds for periods of 1–2 days; time postmortem had no significant effect. The effect of temperature was studied at temperatures of 20, 10, 0, −10, −20, −40 and −75°C using cylindrically shaped samples 3/4 in. in diam × 11/2 in. long. 48 samples were used from 24 7-lb cockerels. Three thermal conductivity measurements were made on each sample at each temperature level. The effect of temperature was similar to that reported in the literature for other meats. The following equations may be used to express the results obtained for white meat: k(Watt/m-°C) = 0.476 + 0.00060T(°C) (0–20°C) and k(Watt/m-°C) = 1.07 − 0149T − 1.04 × 10⁻⁴T²(−75 to −10°C). Similar expressions were obtained for dark meat.     

Microbial flora of technological interest in raw ovine milk during 6°C storage

Changes in the microbial flora of ovine milk of medium hygienic quality (initial mean total plate count 3.3  ×  10⁵ cfu/mL) were studied throughout refrigerated storage at 6°C. Total plate counts after 48 h of refrigerated storage (mean count 4.6  ×  10⁵ cfu/mL) were under the current standards in the European Union (EU) for raw ovine milk to be used for cheesemaking after heat treatment. However, after 96 h, mean total plate counts (1.6  ×  10⁷ cfu/mL) were above the standards. Lactococci were found at levels higher than Pseudomonas spp. in milk freshly drawn (54.5% and 3.5% of total plate count, respectively) and after 96 h at 6°C (47.9% and 33.9% of total plate count, respectively). Lactobacilli, enterococci, coliforms and thermodurics were found at values lower than lactococci and Pseudomonas spp., before and after refrigerated storage ( ≤  0.08% of the total plate count). A significant growth ( P  < 0.001) was detected for mesophiles, Pseudomonas spp. and lactococci after 96 h of refrigeration at 6°C; however, thermodurics, coliforms, lactobacilli and enterococci, showed no significant increase ( P  > 0.05). Presumptive Escherichia coli (β-glucuronidase-positive) underwent a decrease throughout storage at 6°C.     

Determination of Shelf Life of Sous Vide Salmon (Salmo Salard) Based on Sensory Attributes

ABSTRACT:  Sous vide  technology permits precooked dishes of high sensory and nutritional quality to be obtained with a longer shelf life than is possible using other cooking–cooling methods. Salmon portions (200 g; 0.5, w:w; greased with olive oil) were par-roasted (300 °C/3 min), cooked using  sous vide  technology (80 °C/43 min), and maintained in anaerobic conditions at 2 °C for 0, 4, 8, 12, 15, 18, 22, and 25 d. At each control day,  Enterobacteriaceae  counts were made and the attributes of sensory spoilage were determined (3 visual, 2 odor, 2 flavor, and 3 texture attributes) by a panel of trained judges. A loss of smell, taste, color, and juiciness was detected during storage, along with the appearance of off-odors and off-flavors. The shelf life of the  sous vide  salmon based on sensory analysis was established at 18 d.     

Alicyclobacillus acidoterrestris in fruit juices and its control by nisin

Summary The acid-tolerant and heat-resistant bacterium Alicyclobacillus acidoterrestris is a spoilage problem in pasteurized and heat-treated fruit juices. In this study it was shown to grow in orange juice, grapefruit juice and apple juice to produce detectable taint at levels of about 10⁴–10⁵ c.f.u. ml⁻¹. Decimal reduction times were determined at 80 °, 90 ° and 95 °C in each juice and confirmed the heat-resistant nature of the spores under normal juice pasteurization conditions. They also confirmed that heat sensitivity increased with decreasing pH but that this effect was less pronounced at higher temperatures. The organism was, however, sensitive to the bacteriocin food preservative nisin. The presence of nisin during heating decreased the D value by up to 40% and the MIC for nisin against spores at 25 °C was only 5 International Units (IU) ml⁻¹. The results indicate that use of nisin is a potentially useful way of controlling this organism in fruit juices and fruit juice-containing products.     

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.     

Effect of salt concentrations and temperature on the quality and shelf-life of brined anchovies

In this study, the shelf-life and quality of anchovies brined at different concentrations and stored both at refrigerator and ambient temperature conditions were investigated. Sensory, microbiological and chemical analyses of samples were made during storage trials for up to 150 days in order to investigate their quality. The samples stored at ambient temperature showed poor quality at the end of the storage trial. The best quality was observed with the samples that were brined at 22 and 26% salt concentrations, and stored at 4 ± 1 °C.