Microbial shelf-life extension of chilled Coho salmon (Oncorhynchus kisutch) and abalone (Haliotis rufescens) by high hydrostatic pressure treatment

This study was carried out to evaluate the effect of high hydrostatic pressure (HHP) treatment on microbial behavior and the shelf-life extension of Coho salmon and abalone during chilled storage at 4 °C. For salmon, HHP treatments were applied at 135, 170, and 200 MPa for 30 s, while abalone treatment consisted of 500 MPa for 8 min and 550 MPa for 3 or 5 min. Spoilage bacteria (Pseudomonas spp. and hydrogen sulfide-producing bacteria, mainly Shewanella putrefaciens), as well as aerobic mesophilic and psycrophilic microorganisms, were enumerated immediately after treatment and throughout subsequent storage at 4 °C. Results have shown that HHP treatment reduced the initial microbial counts of salmon from 3.16 to 2.2 log units, moreover abalone was reduced from 1.3 log to undetectable levels (<10 CFU g⁻¹). HHP-treatment used for salmon were not sufficient to extend their shelf-life. However, the shelf-life of abalone was extended from 30 (control samples) to >65 days irrespective of HHP treatment applied.     

Shelf-life of pacific white shrimp (Litopenaeus vannamei) as affected by weakly acidic electrolyzed water ice-glazing and modified atmosphere packaging

The combined effect of weakly acidic electrolyzed water (WAEW) ice-glazing and modified atmosphere packaging (MAP) treatment on the quality of pacific white shrimp (Litopenaeus vannamei) during frozen storage was investigated in terms of microbiological activity, TVBN, TMA and TBARS content, texture, color and volatile flavor analysis. As a result, significantly (p < 0.05) higher inhibitor effects on total aerobes and Staphylococcus aureus were observed in WAEW ice-glazed shrimp packaged in 40% CO₂ + 10% O₂ + 50% N₂ or in 30% CO₂ + 20% O₂ + 50% N₂ than the water- and WAEW ice-glazed batches. Additionally, chemical analysis results showed that WAEW ice-glazing combined with MAP was highly effective in maintaining lower TVBN, TMA and TBARS values in frozen shrimp, perhaps due to the synergistic effect of antibacterial and antioxidant abilities. On the other hand, the texture, L^*, and a^* results also confirmed that this combined treatment effectively retarded the degradation of the physical structure of shrimp muscle and showed a positive effect on the stability of color during frozen storage. However, the presence of WAEW ice-glaze showed a negative effect on the volatile flavor of thawed shrimp due to the volatile chlorine and chlorine dioxide, but no significant effect in the cooked samples. Overall, the application of WAEW ice-glazing combined with MAP on peeled frozen shrimp is advisable to achieve better quality maintenance and extend the shelf-life of refrigerated products.     

Application of disinfectant sprays after chilling to reduce the initial microbial load and extend the shelf-life of chilled chicken carcasses

The objective of this study was to evaluate the effects of various disinfectant sprays on initial microbial load and conduct a shelf-life study of chilled chicken carcasses. Chilled chicken carcass samples obtained after chilling were sprayed for 15 s in a purpose-built spray rig with sodium hypochlorite (SH, 50 & 100 mg/L), chlorine dioxide (CD, 50 & 100 mg/L), lactic acid (LA, 1 & 2%), acid electrolyzed oxidizing water (AEOW) and slightly acid electrolyzed oxidizing water (SAEOW). Untreated carcasses were used as the control. Back, leg and breast skin were removed from each carcass after treatment to determine the total viable counts (TVC) and total coliforms. Sprays of 2% LA, AEOW and SAEOW were the most effective treatments with reductions of 0.47–0.83 log CFU/cm² and 0.49–0.96 log MPN/cm² in TVC and total coliforms, respectively. Samples treated with AEOW and SAEOW had 2 days of microbial shelf-life extension compared to the controls, which exceeded the TVC limit of 7 log CFU/cm² at day 6. Even longer extension was obtained for the 2% LA treated samples. The total coliforms, pH and total volatile basic nitrogen (TVBN).TVBN values of the 2% LA, AEOW and SAEOW treated samples were significantly (P < 0.05) lower than those of the controls during storage. Predominantly, the TBARS values of the AEOW and SAEOW treated samples were not statistically different from those of the controls (P > 0.05); however, the 2% LA treatment accelerated lipid oxidization, manifested as the highest TBARS value (2.09 mg MDA/kg) at day 8. Conclusively, this study indicated that the application of AEOW and SAEOW sprays to chilled chicken carcasses after chilling can reduce initial microbial load and maintain quality attributes during refrigerated storage.     

Development of Quality Index Method (QIM) scheme for spiny lobster (Panulirus argus,Latreille, 1804) stored in ice

The objective of this study was to evaluate the freshness of spiny lobster (Panulirus argus) stored on ice up to 18 days. Changes during storage were observed with sensory evaluation (Quality Index Method – QIM), pH, total volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), and microbiological analyses (total mesophilic and psychrotrophic count). The maximum shelf life of spiny lobster stored in flake ice at 1 ± 0.2 °C was determined with loss of freshness (sensorial, physico-chemical and microbiological evaluations). High correlation R² = 0.922 between Quality Index (QI) and storage time at 1 °C was verified. QI ranged from zero (maximum freshness) to 15 (total loss of freshness) and reached the acceptable limit for consumption (QI = 9.54), which corresponds to a period of 10 days. The microbiological results showed an increase of psychrotrophic count along the storage time. TVB-N ranged from 5.23 to 20.31 mg 100 g⁻¹, TMA-N from 1.07 to 5.72 mg 100⁻¹ and pH from 6.91 to 7.19 in the first and 18th day of storage, respectively. It is suggested that spiny lobster has to be fresh and acceptable for consumption by cooling up to 10 days.     

Changes in the microbiological and physicochemical quality of high-pressure-treated oysters (Crassostrea gigas) during chilled storage

Changes in the physicochemical and microbiological quality of oysters HP-treated at 260, 400 or 600 MPa for 5 min and stored at 2 °C on ice for 31 days were investigated. Microbial counts after HP treatment showed that the bacterial load was initially reduced at all pressures to levels below the detection limit. HP-treated oysters showed significantly increased pH and lightness (P < 0.05) relative to untreated oysters; during storage, pH changed little in the pressurised oysters but decreased slightly in untreated oysters. Little changes in colour were observed during storage at 2 °C on ice, compared to untreated oysters, which showed increased b-values (stronger yellow colour). From tests of mechanical properties, HP-treated oysters showed significantly increased cutting strength (P < 0.05) with increasing treatment pressure compared to controls throughout storage. However, HP increased lipid oxidation, the rate of which was dependent on the pressure applied. This study confirmed that HP processing can inactivate microorganisms and delay microbial growth in chilled stored oysters, but also affects their quality attributes.     

Quality assessment of Mediterranean horse mackerel (Trachurus mediterraneus) and blue jack mackerel (Trachurus picturatus) during storage in ice

Sensory, physicochemical and microbiological analyses were carried out on Mediterranean horse mackerel and blue jack mackerel in order to determine quality changes during storage in ice. Sensory results indicated that whole Mediterranean horse mackerel and blue jack mackerel used in this trial had a shelf-life of 10 and 7 days, respectively. Fishtester and Fishchecker measurements showed that the quality of blue jack mackerel had deteriorated more rapidly. Fishtester values of the blue jack mackerel and the Mediterranean horse mackerel were reduced from 59 ± 10.1 to 14.8 ± 2.8 and from 85.3 ± 13.2 to 25.6 ± 7.8, respectively during the storage time. Fishchecker gave red sign (unfit for consumption) for first time on day 7 and day 6 in Mediterranean horse mackerel and blue jack mackerel, respectively. The pH of Mediterranean horse mackerel muscle was consistently lower than the pH of blue jack mackerel muscle during the storage period. The pH values of both species muscle increased gradually with time and pH value equal to 7 had almost coincided with the end of shelf-life. Bacterial loads in both fish species muscle remained rather low prior to day 10 (<6 log₁₀ cfu/g). The longer shelf-life of Mediterranean horse mackerel as determined by sensory evaluation was not reflected in microbiological results suggesting that the difference was due to lower rate of autolysis rather than to reduced microbial activity.     

Effects of high hydrostatic pressure processing on purine,taurine, cholesterol,antioxidant micronutrients and antioxidant activity of squid (Todarodes pacificus) muscles

This study investigated the effect of high hydrostatic pressure processing (HHP, at 0.1 [control], 200, 400 or 600 MPa) on purine, taurine, cholesterol, antioxidant micronutrients (Mn, Se, Fe, Zn, Cu, vitamin B₂, A and E), DPPH, and reducing power of squids during 10-day storage at 4 °C. Compared with the control, pressurization did not change the contents of purine, vitamin A and E, Mn and Fe in the squid samples on day 0. After 10-days of storage, HHP at 600 MPa caused maximum decreases in cholesterol, hypoxanthine, adenine and Fe, and produced small reductions in guanine, vitamin B₂, DPPH, reducing power, and TBARS. No significant differences were found in cholesterol, reducing power, vitamin B₂ or A between 200 MPa and 400 MPa treated samples. Both pressurization and storage time did not affect the levels of taurine, DHA, EPA, Mn and Cu. This study provided a strategy to decrease the cholesterol and purine contents with minimal antioxidant activity loss in seafood using HHP.     

Microbiological changes in farm reared freshwater prawn (Macrobrachium rosenbergii de Man) in ice

The microbiological changes in farm reared freshwater prawn (Macrobrachium rosenbergii de Man) during ice storage were studied. A total of 156 bacterial cultures from fresh and ice-stored farmed freshwater prawn were isolated and characterized. Total aerobic, mesophilic and psychrotrophic counts and hydrogen sulphide producing bacterial counts were determined. The total aerobic counts at 20 and 37 °C on fresh prawn was in the range of 4–5 log₁₀ cfu g⁻¹. Aerobic counts on M. rosenbergii at 20 °C and 7 °C exceeded 10⁷ cfu g⁻¹ by the end of storage, of which 40–52% were H₂S producers. Gram-negative bacteria constituted 73% of the total flora of fresh prawn and Enterobacteriaceae and Aeromonadaceae dominated. After 19 days of iced storage, more than 80% of the bacterial flora of prawn were Gram-negative. Pseudomonas, Aeromonas hydrophila, A. veronii boivar sobria and Shewanella putrefaciens were identified as the dominant spoilage organisms of farm reared M. rosenbergii stored in ice. This study confirms that freshwater prawn carry significant numbers of motile aeromonads capable of growth at low temperature. The results of the study indicated that the shelf-life of freshwater prawn as determined by microbiological data is 12–16 days. Immediate icing of harvested M. rosenbergii is essential to improve the microbiological stability.     

The effect of mild preservation treatments on the invasiveness of different Listeria monocytogenes strains on Greenshell™ mussels

High pressure processing (HPP) and thermal treatments are food preservation technologies used by the food industry to inactivate Listeria monocytogenes. However, the safe shelf-life of treated products could be compromised by the presence and/or recovery of surviving bacteria. The aim of the present study was to evaluate the effect of these technologies on the invasion capacity of L. monocytogenes. Eleven L. monocytogenes strains (serovars 1/2a,1/2b,1/2c and 4b) isolated from food processing plants and food products were grown in culture media, associated with Greenshell™ mussel surfaces and subjected (or not) to HPP (350 MPa, 2 min) or mild heating (MH, 55 °C, 10 min). The invasiveness of the strains was compared immediately after processing and after 14 days of storage at 8 °C using human intestinal epithelial Caco-2 cells. All strains on mussels had decreased invasion capacity compared with those coming directly from culture media. Invasiveness of L. monocytogenes also decreased immediately after pressurization but returned to the rate in untreated samples after 14 days of refrigerated storage. In contrast, MH did not affect invasion capacity, and treated samples showed the same rates as non-MH treated ones. Lineage I strains were more invasive than lineage II strains after both mild processing treatments. Based on these results, the risk of L. monocytogenes infection by the consumption of treated mussels will not be increased, as the invasiveness of possible survivors is not increased.     

Single- and multi-cycle high hydrostatic pressure treatment on microbiological quality of mud snail (Bullacta exarata) during refrigerated storage

High hydrostatic pressure (HHP) processing is an industrial technology used for preservation of a wide range of food products, and vacumm-packed mud snails (Bullacta exarata) were HHP processed to ensure food safety and shelf-life stability. The effects of single- and multi-cycle HHP treatment, especially the combination of different intensities, on the microbial behavior and shelf-life extension of B. exarata during subsequent storage were investigated. Total microbial count, psychrophilic microorganisms, Clostridium bacteria, total Enterobacteriaceae and H₂S-producing bacteria were enumerated during subsequent refrigerated storage, and Gompertz model was chosen to predict the shelf-life, growth rate, lag time and generation time. The results showed that the initial microbial load was obviously reduced as the pressure increased. Total Enterobacteriaceae and H₂S-producing bacteria were not detected in multi-cycle HHP processing during refrigerated storage. Moreover, multi-cycle HHP method (B + F) could improve the shelf-life of B. exarata for more than 38 days. The model indicated that the lag time for Clostridium bacteria processed with multi-cycle HHP (B + F) was extended to 24.65 days. Our findings will be of aid for the establishment of general process guidelines, and demonstrated that multi-cycle HHP technology has potential for application in mud snail preservation and processing.     

Development of new quality index method (QIM) schemes for cuttlefish (Sepia officinalis) and broadtail shortfin squid (Illex coindetii)

This article describes the development of sensory schemes for freshness grading of cuttlefish (Sepia officinalis) and broadtail shortfin squid (Illex coindetii) based on the recent quality index method (QIM). As preliminary work, four storage experiments were performed to choose the relevant sensory parameters for building the schemes. From an initial large set of parameters, some were chosen to be attributes for the QIM scheme. For cuttlefish, appearance, odour and mucus of skin, texture of flesh, cornea and pupil transparency, odour of the mouth region and connection between bone and head tissues; and for squid, appearance, odour and mucus of skin, texture of flesh, appearance of the eyes and ocular tissue brightness and odour of the mouth region. Five storage experiments were then used to test the tables and to shelf-life studies. The shelf-life, as measured by sensory attributes, is considered to be 10 days in ice for cuttlefish and 9 days in ice for squid. Sensory and shelf-life differences between these two species can be explained by morphological and biological reasons that probably include higher rigidity of the cuttlefish caused by the presence of the internal bone. For both species a high correlation between the quality index and the storage time in ice was obtained.     

Combined effect of electrolyzed oxidizing water and chitosan on the microbiological,physicochemical, and sensory attributes of American shad (Alosa sapidissima) during refrigerated storage

This study evaluated the combined effect of electrolyzed oxidizing water (EOW) and chitosan (CH) on the quality and shelf-life of American shad (Alosa sapidissima) stored at 4 °C for 25 days. A CH solution (2% w/v; pH 3.7) was used to coat the fish flesh after washing with EOW (pH 2.4; oxidation-reduction potential, 1185 mV; free chlorine level, 70–80 ppm). Control and treated fish samples were analyzed for microbiological (total viable count), physicochemical (pH, total volatile basic nitrogen, thiobarbituric acid, texture, and color), and sensory characteristics. The results revealed that EOW + CH was more effective than either treatment alone (EOW or CH) in inhibiting microbial growth, protein decomposition, and lipid oxidation. Furthermore, EOW + CH maintained better texture, color, and sensory characteristics of fish. This treatment extended the shelf-life of American shad fillets by 9–10 days during refrigerated storage.     

High pressure processing extend the shelf life of fresh salmon,cod and mackerel

High pressure processing (HPP) is used on several types of seafood, though its potential for extending the shelf life of fresh fish has not been fully exploited. This study compared the effect of HPP (200 and 500 MPa, 120 s) on salmon, cod and mackerel. Immediately after processing, and during storage up to 26 days different analysis were carried out to evaluate the microbiological shelf life, oxidation, acid phosphatase level and pH of the different fish species during the storage period. For cod and mackerel, HPP at 500 MPa restrained the bacterial flora and it did not reach spoilage level, opposite to the salmon samples exposed to 500 MPa. Analysis of TBARS is often used as a measure of lipid oxidation. The TBARS-level was differently affected by pressure in salmon and cod. HPP at 200 MPa did not have any effect on the oxidation level in salmon during the storage period while this was observed for cod. The TBARS level in mackerel was high, independent of pressure treatment or not. Phosphatase activity in fish has been suggested to be related to freshness. The acid phosphatase (ACP) levels in control samples showed significant differences between salmon and cod. For salmon both control and samples treated at 200 MPa showed a decrease in ACP level at day 11 compared with day 0, whereas the HPP500 values were even throughout the study. This latter observation was also the case for cod treated at 500 MPa. This study have shown that HPP induce different levels of changes in various fish species.     

Effect of high pressure treatments on smoked cod quality during refrigerated storage

The effect of high pressure (HP) treatments on microbiological, chemical, textural and sensory characteristics of vacuum-packaged cold-smoked cod refrigerated at 5 °C for 60 d was evaluated. HP at 400, 500 and 600 MPa for 5 and 10 min reduced microbial counts of smoked cod and delayed microbial growth during refrigerated storage. No differences in lipid oxidation estimated as thiobarbituric acid reactive substances (TBARS) were observed after pressurization and during refrigeration. Only tryptamine and spermine at very low levels were detected among biogenic amines in smoked cod. High pressure treatments induced a brighter appearance of smoked cod, with higher values of L∗ and b∗, whereas a∗ values decreased with pressurization. HP affected hardness and shear strength of smoked cod, with higher values after treatment, but differences with untreated smoked cod were attenuated during the storage period. No differences in overall appearance and odor of smoked cod were reported after sensory evaluation. The results obtained in the present work point to the usefulness of pressurization of smoked cod at 400 MPa for 10 min or 500 MPa for 5 min to obtain an acceptable product with extended shelf-life. HP might increase the safety and protect the product against possible pathogen contamination during processing.     

The influence of superchilling storage methods on the location/distribution of ice crystals during storage of Atlantic salmon (Salmo salar)

The objective of this work was to study the influence of superchilling storage methods, shell freezing and non-shell freezing on the location/distribution of ice crystals during the superchilled storage of salmon. Physical measurements, water holding capacity and drip loss were also studied. Non-shell frozen samples resulted in extracellular ice crystals. Shell frozen samples showed both intracellular and extracellular ice crystals with a uniform distribution. Liquid loss (LL) decreased with storage time in both superchilling storage methods. There was no significant difference (p > 0.05) in LL between shell and non-shell frozen samples. There was significant difference (p < 0.05) in the drip loss between shell frozen samples (1.62% as maximum) and non-shell frozen samples (1.4% as maximum). The information on the characteristics of ice crystals (location/distribution), which has a strong influence on the quality of the final superchilled food, is a factor key for the manufacturing of products with desired quality and shelf life.     

Inactivation of Salmonella spp. in ground chicken using high pressure processing

High Pressure Processing (HPP) is a safe and effective process for improving the microbial safety and shelf-life of foods. Salmonella is a common contaminant in poultry meat and is frequently responsible for foodborne illness associated with contaminated poultry meat. In this study the inactivation of a five-isolate cocktail of Salmonella spp. in ground chicken (95% lean) using HPP at refrigeration temperature (4–6 °C) was studied. More than 5-log CFU/g inactivation was achieved at 450 MPa for10 min. In contrast, HPP treatment at 250 MPa or 350 MPa (single-cycle, 15 min) inactivated 0.5 log or 1.7 log CFU/g, respectively. The multiple-cycle HPP mode at 250 or 350 MPa (3-cycle with 5 min/cycle) showed higher cell reduction at 1.3 or 3.3 log CFU/g, respectively. HPP at 550 MPa for 10 min may reduce the cell counts, initially at 8.5 log CFU/g, to below the detection limit (1.0 log CFU/g) in current study. The images (electron microscopy) of the HPP shocked cells were examined for structural damage, which demonstrated that Salmonella cells may still look intact (with damages on rough/irregular surface at 450 MPa stress) under Scanning Electron Microscopy (SEM), but have significant damage internally (voids and uneven mass distribution patterns) under Transmission Electron Microscopy (TEM).     

Quality by design for packaging of granola breakfast product

Quality by Design (QbD) considers both the critical product characteristics and the environmental variables to design an optimum packaging system. This study applied the QbD approach for packaging and shelf-life determination of Granola by i) determining the water vapour transmission rate (WVTR) of packaging films at different environmental conditions, ii) develop and validate a shelf-life model of packed granola breakfast product and iii) predict shelf-life of packed Granola. The WVTR of packaging films (BOPP and biodegradable films, i.e., NK, NM, N913) was measured according to a full factorial experimental design (3²), i.e., 10, 30, 40 °C; 32.5 ± 0.5, 75.5 ± 0.5, 92.5 ± 3.5% RH, and a mathematical model was developed. Granola breakfast product was packed (using the mentioned materials and also a commercial packaging film-control), stored under accelerated conditions (38 °C and 90% RH) and assessed for moisture content (critical quality parameter). A shelf-life model was developed and validated for Granola describing the relationship of the food, packaging and environmental conditions, and shelf-life was inferred for normal storage conditions. The developed WVTR global model considering the dependency of temperature and relative humidity was found to fit the experimental data well (R² > 0.914). Granola moisture gain was the lowest in BOPP package followed by biodegradable N913 package. The shelf-life for Granola under accelerated conditions ranged from 2 to 13 days depending on the packaging film, and under normal storage conditions (20 °C and 75% RH) was 271, 269, 90, and 33 days for BOPP, N913, NK and NM packages, respectively.     

Effect of isothiocyanates from horseradish (Armoracia rusticana) on the quality and shelf life of tofu

The effects of isothiocyanates (ITCs) on microbiological, physicochemical, and sensory properties were investigated in tofu on days 0, 2, 4, 6, 8, and 10 of storage at 10 °C. When compared to the control (8.14 log CFU/g), the 200 ppm of ITCs (4.40 log CFU/g) effectively retarded the growth of microflora in tofu after 10 days of storage. The initial pH slightly declined after 10 days of storage, ranging between 5.81 and 6.14. The control showed significantly higher acid values over storage. Compared to the control, the preference to sensory attributes (color, taste, odor, chewiness, and over acceptance) of ITC-treated samples was highly rated after 10 days of storage. The ITCs can be used as an alternative for extending the shelf life and improving the safety of tofu.     

Total volatile base nitrogen and its use to assess freshness in European sea bass stored in ice

During a study on shelf life, different parameters were analyzed. For this reason, one group of farm raised European sea bass (Dicentrarchus labrax) from Canary Islands (Spain) sea waters were stored in melting ice for a period of 21 days from the time of harvest. The samples were assessed for their total volatile basic nitrogen contents (TVBN) at regular intervals (0, 2, 4, 7, 10, 14, 18 and 21 days). There was practically no change in the level of TVBN during the edible storage life of the fish. After obtaining poor results in this first experiment, another group of sea bass were studied for a period up to 21 days (0, 2, 4, 7, 10, 14, 18, 21, 24 and 28) out of their shelf life time. This new set showed an increase of volatile bases after 20–22 days of storage.This experiment demonstrates unlike previous ones there exists an evolution of the volatile bases but out of its shelf life. This retarded evolution prevents the use of the TVBN limits as a test. TVBN should be considered a very unreliable indicator by freshness with European sea bass and it must not be used in its application as a reference method to refuse sea bass in markets.     

The control of Clostridium botulinum during extended storage of pressure-treated,cooked chicken

High pressure processing (HPP) is used as a post-process decontamination treatment to ensure that cooked chicken is free from Listeria monocytogenes and other food poisoning bacteria. However HPP does not inactivate bacterial endospores and the conditions in cooked chicken could support the growth of Clostridium botulinum. Therefore some method for controlling the germination of spores and their subsequent growth would be necessary to ensure a safe product over an extended storage period.A five strain cocktail of non-proteolytic C. botulinum was inoculated into raw chicken mince, which was cooked and then pressure treated at 600 MPa for 2 min at 20 °C. C. botulinum survived cooking and HPP and subsequently grew in the pressure-treated, cooked chicken during storage. Germination and growth was controlled when 2% w/w sodium lactate was added and when oxygen-permeable packaging was used. Weissella viridescens was not suitable for use as a protective culture to control the growth of C. botulinum.