Natural compounds to preserve fresh fish burgers

Natural antimicrobial compounds to control the quality decay of a fresh fish burger were studied. In particular, thymol, lemon extract and grape fruit seed extract (GFSE), at 20, 40 and 80 ppm, have been tested against the main spoilage microorganisms inoculated in fish burgers stored at 5 °C. The evolution of mesophilic and psychrotrophic bacteria was also monitored. The sensorial quality decay was determined by means of a panel test, which assessed odour, colour, texture, drip loss and general appearance during the storage period. Results show that all the active substances efficiently slowed down the growth of the spoilage microorganisms. In particular, GFSE was the most efficient against Photobacterium phosphoreum , Shewanella putrefaciens and mesophilic bacteria, whereas thymol was the most efficient against both psychrotrophic bacteria and Pseudomonas fluorescens . Microbial growth was the factor limiting fresh fish burger acceptability.     

Use of Desirability Approach to Predict the Inhibition of Pseudomonas fluorescens, Shewanella putrefaciens and Photobacterium phosphoreum in Fish Fillets Through Natural Antimicrobials and Modified Atmosphere Packaging

The main goal of this paper was the prolongation of the microbiological acceptability limit (MAL) of gilthead sea bream fillets, added with some natural antimicrobials and packed under modified atmosphere; desirability approach was used, and the research was divided into two different steps. The first phase addressed fish fillet preservation through chitosan (0–4 %), grape fruit seed extract (GFSE) and thymol (0–6,000 ppm); Pseudomonas fluorescens, Shewanella putrefaciens and Photobacterium phosphoperum, inoculated onto the surface of fillets, were used as microbial targets. The concentration of the three antimicrobials were combined through a three variables/five levels central composite design; after fish inoculation and dipping into active solutions containing the natural compounds, fillets were stored at 4 °C and analysed periodically. Data of microbiological counts were fitted through a primary model (modified Gompertz equation), for the evaluation of MAL; MALs were used to build a polynomial model, able to draw a desirability profile for each antimicrobial. These outputs (desirability and polynomial equation) highlighted that Pseudomonas fluorescens was the most resistant microorganism; it could be inhibited through an active solution containing 2 % of chitosan and 6,000 ppm of GFSE and thymol. Therefore, in the second step of the research, fish fillets were dipped in this active solution and packed under two different atmospheres (30:40:30 O₂/CO₂/N₂ and 5:95 O₂/CO₂) and stored at 4 °C. For each microorganism, the stability time was evaluated, thus pointing out that the best sample was that packed under 5:95 O₂/CO₂.     

Study on the synergic effect of natural compounds on the microbial quality decay of packed fish hamburger

The effectiveness of natural compounds in slowing down the microbial quality decay of refrigerated fish hamburger is addressed in this study. In particular, the control of the microbiological spoilage by combined use of three antimicrobials, and the determination of their optimal composition to extend the fish hamburger Microbiological Stability Limit (MAL) are the main objectives of this work. Thymol, grapefruit seed extract (GFSE) and lemon extract were tested for monitoring the cell growth of the main fish spoilage microorganisms (Pseudomonas fluorescens, Photobacterium phosphoreum and Shewanella putrefaciens), inoculated in fish hamburgers, and the growth of mesophilic and psychrotrophic bacteria. A Central Composite Design (CCD) was developed to highlight a possible synergic effect of the above natural compounds. Results showed an increase in the MAL value for hamburgers mixed with the antimicrobial compounds, compared to the control sample. The optimal antimicrobial compound composition, which corresponds to the maximal MAL value determined in this study, is: 110 mgL(-1) of thymol, 100 mgL(-1) of GFSE and 120 mgL(-1) of lemon extract. The presence of the natural compounds delay the sensorial quality decay without compromising the flavor of the fish hamburgers.     

Combined effects of thymol, carvacrol and temperature on the quality of non conventional poultry patties

The combined effect of thymol (0–300 ppm), carvacrol (0–300 ppm), and temperature (0–18 °C) on the quality of non conventional poultry patties packaged in air and modified atmosphere (MAP: 40% CO_2; 30%O₂; 30% N₂) was investigated using a simplex centroid mixture design. The patties were monitored for microbiological (total viable count, Enterobacteriaceae, lactic acid bacteria, Pseudomonas spp.) physico-chemical (pH, colour) and sensory attributes. For the patties mixed with the antimicrobials and stored at low temperature (0–3 °C) a reduction of the cell load of about 1–1.5 log cfu/g was observed. The log reduction was lower at the end of storage time and decreased with the increase of the temperature. For the poultry patties packaged in MAP the higher log reduction for Pseudomonas spp. during all the storage time was observed. In both packaging atmospheres the combination of the essential oils and low temperature determined no modification for off-odour during the first 4 days of storage.     

Shelf life of ready to use peeled shrimps as affected by thymol essential oil and modified atmosphere packaging

In this work the influence of different packaging strategies on the shelf life of ready to use peeled shrimps was investigated. First, the effectiveness of the coating (Coat) and the active coating loaded with different concentrations of thymol (Coat-500, Coat-1000, and Coat-1500) on the quality loss of the investigated food product packaged in air was addressed; afterwards, the thymol concentration that had shown the best performance was used in combination with MAP (5% O₂; 95% CO₂). Microbial cell load of main spoilage microorganisms, pH and sensorial quality were monitored during the refrigerated storage. Results of the first step suggested that the sole coating did not affect the microbial growth. A slight antimicrobial effect was obtained when the coating was loaded with thymol and a concentration dependence was also observed. Moreover, the active coating was effective in minimizing the sensory quality loss of the investigated product, it was particularly true at the lowest thymol concentration. In the second step, the thymol concentration (1000 ppm) that showed the strike balance between microbial and sensorial quality was chosen in combination with MAP. As expected, MAP significantly affected the growth of the mesophilic bacteria. In particular, a cell load reduction of about 2 log cycle for the samples under MAP respect to that in air was obtained. Moreover, the MAP packaging inhibited the growth of the Pseudomonas spp. and hydrogen sulphide-producing bacteria. The MAP alone was not able to improve the shelf life of the uncoated samples. In fact, no significant difference between the control samples packaged in air and MAP was observed. Whilst, the use of coating under MAP condition prolonged the shelf life of about 6 days with respect to the same samples packaged in air. Moreover, when the MAP was used in combination with thymol, a further shelf life prolongation with respect to the samples packaged in air was observed. In particular, a shelf life of about 14 days for the active coating under MAP compared to the same samples in air (5 days) was obtained.     

Use of natural compounds to improve the microbial stability of Amaranth-based homemade fresh pasta

A study on the use of natural antimicrobial compounds to improve the microbiological stability of refrigerated amaranth-based homemade fresh pasta is presented in this work. In particular, the antimicrobial activity of thymol, lemon extract, chitosan and grapefruit seed extract (GFSE) has been tested against mesophilic and psychrotrophic bacteria, total coliforms, Staphylococcus spp., yeasts and moulds. A sensory analysis on both fresh and cooked pasta was also run. Results suggest that chitosan and GFSE strongly increase the microbial acceptability limit of the investigated spoilage microorganisms, being the former the most effective. Thymol efficiently reduces the growth of mesophilic bacteria, psychrotrophic bacteria and Staphylococcus spp., whereas it does not affect, substantially, the growth cycle of total coliforms. Lemon extract is the less effective in preventing microbial growth. In fact, it is able to delay only total mesophilic and psychrotrophic bacterial evolution. From a sensorial point of view no significant differences were recorded between the control samples and all the types of loaded amaranth-based pasta.     

Improved keeping quality of minimally fresh processed celery sticks by modified atmosphere packaging

Recommended storage conditions of green celery sticks are 4 °C for 10 days, but there are no reports about optimal modified atmosphere packaging (MAP) conditions to preserve them longer. The objective of this research was to describe the gas composition of MAP generated by two polymeric films and its effects on chemical, sensorial and microbial quality, and physiological disorders of celery sticks stored at 4 °C for 15 days. Green sticks of 15-cm length of ‘Trinova’ cv. were placed in hermetically sealed plastic bags: low-density polyethylene, oriented polypropylene (OPP) and polyethylene-perforated bags as control (air). The O₂ and CO₂ concentrations, soluble solid content, pH, titratable acidity, colour, sensorial quality and sugar and organic acids contents were monitored. Compared to the control, both MAP treatments improved the sensory quality, avoided the loss of green colour, decreased the development of pithiness and retarded the growth of microorganisms. In any treatment neither off-odours nor off-flavours were detected. After 15 days at 4 °C within the OPP bags a steady-state atmosphere of 6 kPa O₂+7 kPa CO₂ was reached and celery sticks stored under these bags showed the best quality.     

Preservation of precut white cheese by modified atmosphere packaging

Effects of modified atmosphere packaging (MAP) on storage stability and quality of precut fresh and aged white cheese were investigated. Fresh or aged white cheese was cut into small cubes and packaged in five different atmospheres [0% O₂ + 0% CO₂ + 100% N₂ (MAP1), 10% O₂ + 0% CO₂ + 90% N₂ (MAP2), 0% O₂ + 75% CO₂ + 25% N₂ (MAP3), 10% O₂ + 75% CO₂ + 15% N₂ (MAP4) and aerobic (air)]. Control samples were packaged in brine and vacuum for fresh and aged white cheese, respectively. Changes in gas composition, total plate count, lactococci, lactobacilli, yeast and mould counts, proteolysis, lipolysis, pH, colour, texture and sensory properties were investigated during refrigerated storage. The best packaging treatment for the fresh cheese was MAP3, as it inhibited mould growth and protected the hardness. MAP2 can be recommended for the packaging of the aged cheese, as it decreased lipolysis.     

Active coating and modified-atmosphere packaging to extend the shelf life of Fior di Latte cheese

In this work the combination of active coating and modified-atmosphere packaging (MAP) was used to prolong the shelf life of Fior di Latte cheese. The active coating was based on sodium alginate (8% wt/vol) containing lysozyme (0.25 mg/mL) and EDTA, disodium salt (Na₂-EDTA, 50 mM). The MAP was made up of 30% CO₂, 5% O₂, and 65% N₂. The speed of quality loss for the Fior di Latte cheese, stored at 10°C, was assessed by monitoring pH and weight loss, as well as microbiological and sensorial changes. Results showed that the combination of active coating and MAP improved Fior di Latte cheese preservation, increasing the shelf life to more than 3 d. In addition, the substitution of brine with coating could allow us to gain a double advantage: both preserving the product quality and reducing the cost of its distribution, due to the lower weight of the package.     

Postharvest performance of fresh‐cut ‘Big Top’ nectarine as affected by dipping in chemical preservatives and packaging in modified atmosphere

Fresh‐cut ‘Big Top’ nectarines were dipped in 2% (w/v) ascorbic acid–1% (w/v) calcium lactate and stored at 4 °C for up to 12 days in 10 kPa O₂‐ and 10 kPa CO₂‐modified atmosphere packaging (MAP). The used microperforated plastic film allowed O₂ and CO₂ concentrations to reach steady values from the fifth day in storage onwards. Samples stored in MAP after chemical dipping showed the highest visual quality score, slight browning symptoms, increment in firmness and very low ethanol and acetaldehyde content. The chemical dipping also increased antioxidant capacity, probably due to the effect of ascorbic acid. The results suggested that the control of yeasts was mainly exerted by MAP, whereas only a slight effect was achieved by the chemical dipping. Therefore, MAP plus ascorbic acid/calcium lactate dipping was the best combination to preserve phytochemical content, antioxidant capacity and microbiological safety of fresh‐cut nectarines during storage.     

Tuna Burgers Preserved by the Selected <Emphasis Type="Italic">Lactobacillus paracasei</Emphasis> IMPC 4.1 Strain

The use of protective microbial strains in combination with modified atmosphere packaging (MAP) and refrigerated storage on the shelf life of tuna burgers was investigated. Preliminary, the protective ability of three lactic acid bacteria (LAB) cultures (Lactobacillus casei, Lactobacillus paracasei, and Lactobacillus plantarum) have been assessed on ready-to-cook tuna burgers. Among them, L. paracasei showed the best preserving performance and significantly controlled both aerobic mesophilic bacteria and Pseudomonas spp. growth. Subsequently, the efficacy of the selected LAB culture under MAP conditions (5% O₂ and 95% CO₂) was assessed evaluating microbial and sensory quality, as well as volatile aldehyde content. Results indicated that the shelf life of burgers containing L. paracasei and packaged under MAP was 4 days longer than the control (shelf life about 6 days) and that the applied procedure represents an effective approach for the mild preservation of fish products.     

Combined effects of chitosan and MAP to improve the microbial quality of amaranth homemade fresh pasta

In this work a study on the combined effects of chitosan and modified atmosphere packaging (MAP) to improve the microbiological quality of amaranth-based homemade fresh pasta is presented. In particular, two different chitosan concentrations were combined to three different MAP conditions and tested against the following spoilage microorganisms: mesophilic bacteria, Staphylococcus spp., yeasts, moulds and total coliforms. Their viable cell concentrations were monitored for about 2 months at 4 °C. Results suggest that there is a combined effect between MAP and chitosan in delaying the microbial quality loss of pasta during storage. Moreover, it was also found that among the tested MAP conditions, the combination of 30:70 N₂:CO₂ is the most efficient, promoting an extension of the microbial acceptability limit beyond two months.     

Effects of novel modified atmosphere packaging on lipid quality and stability of sardine (Sardina pilchardus) fillets

Modified atmosphere packaging (MAP) is an efficient method to increase shelf-life of fishery products by inhibiting bacterial growth and oxidative reactions. Beside the traditional gases used for MAP, novel gases such as argon (Ar) and nitrous oxide (N₂O) were approved for food use in the European Union. The present research investigates the effect of MAP with unconventional gas mixtures, that previously positively affected microbial shelf-life, on colour, lipid oxidation and sensorial characteristics of sardine fillets during storage. Four atmosphere conditions were tested: Air (20.8% O₂/79.2% N₂), N₂ (30% CO₂/70% N₂), N₂O (30% CO₂/70% N₂O) and Ar (30% CO₂/70% Ar). Samples were stored for 12 days at 3 °C. Results showed that the removal of oxygen significantly inhibited the oxidation process; however, most of the investigated parameters related to fat oxidation did not show any improvement, except for a slight decrease in lipid hydrolysis and improvement in sensory properties in the packaging containing Ar.     

Effect of modified atmosphere and temperature abuse on the growth from spores and cereulide production of Bacillus weihenstephanensis in a cooked chilled meat sausage

The effect of modified atmosphere packaging (MAP) on the germination and growth of toxin producing psychrotolerant Bacillus spp is not well described. A model agar system mimicking a cooked meat product was used in initial experiments. Incubation at refrigeration temperature of 8 °C for 5 weeks of 26 Bacillus weihenstephanensis including two emetic toxin (cereulide) producing strains showed that B. weihenstephanensis is sensitive to MAP containing CO₂. The sensitivity to 20% CO₂ was dependent on strain and oxygen level, being increased when oxygen was excluded from the MAP. Growth from spores was observed at the earliest within 2 weeks when 20% CO₂ was combined with 2% O₂ and in 3 weeks when combined with “0”% O₂ (the remaining atmosphere was made up from N₂). Results were validated in a cooked meat sausage model for two non-emetic and one emetic B. weihenstephanensis strain. The packaging film oxygen transfer rates (OTR) were 1.3 and 40 ml/m²/24 h and the atmospheres were 2% O₂/20% CO₂ and “0”% O₂/20% CO₂. Oxygen availability had a large impact on the growth from spores in the MAP meat sausage, only the most oxygen restricted condition (OTR of 1.3 ml/m²/24 h and “0”% O₂/20 % CO₂) inhibited growth of the three strains during 4 weeks storage at 8 °C. Cereulide production was undetectable during storage at 8 °C irrespective of choice of the MAP (quantified by liquid chromatography mass spectrometry/mass spectrometry). MAP storage at 8 °C for 1 and 3 weeks followed by opening of packages and temperature abuse for 1.5 h daily at 20 °C during 1 week resulted in increased cell counts and variable cereulide production in the meat sausage. A pre-history at 8 °C for 1 week in MAP with OTR of 1.3 or 40 ml/m²/24 h and 2% O₂ resulted in cereulide concentrations of 0.816 – 1.353 µg/g meat sausage, while a pre-history under the most oxygen restricted condition (OTR of 1.3 ml/m²/24 h, “0”% O₂/20 % CO₂) resulted in minimal cereulide production (0.004 µg/g meat sausage) at abuse condition. Extension of MAP storage at 8 °C for 3 weeks followed by abuse resulted in a substantially reduced cereulide production.Data demonstrates that MAP can be used to inhibit growth of a psychrotolerant toxin producing Bacillus spp. during chill storage at 8 °C, and substantially reduce the risk of emetic food poisoning at abuse condition. Results are of relevance for improving safety of ready to eat processed chilled foods of extended durability.     

Modelling the effect of gas composition on the gas exchange rate in Perforation-Mediated Modified Atmosphere Packaging

Modified Atmosphere Packaging (MAP) relies on modification of the atmosphere inside a package, achieved by the natural interplay between the respiration of the product and the transfer of gases through the package. Polymeric films are the most usual packaging material but because of the increase in the consumption of fresh-cut products with a higher respiration rate and higher tolerance to CO₂, alternative materials are being investigated. The perforation-mediated package is one of those alternatives, where the regulation of the gas exchange is achieved by single or multiple tubes that perforate an otherwise impermeable packaging material. From an engineering point of view, the transport of gases through perforations is a complex phenomenon that involves diffusion gradients together with co-current transport of multiple species, with oxygen entering the package and carbon dioxide leaving it. The influence of one species transport in the other has not been studied so far. The objective of this work was to analyse the effect of initial concentration of CO₂ on the effective mass transfer coefficients of O₂ (K_O2) and CO₂ (K_CO2) in perforation-mediated MAP. K_O2 ranged from (6.99 ± 0.05) × 10⁻⁸ (m³ s⁻¹) to (28.50 ± 0.01) × 10⁻⁸ (m³ s⁻¹) and for K_CO2 from (6.45 ± 0.04) × 10⁻⁸ (m³ s⁻¹) to (28.32 ± 0.01) × 10⁻⁸ (m³ s⁻¹). On average K_O2 decreased by approximately 15% with an increase of CO₂ initial concentration from 25% to 100%. K_CO2 was insensitive to the composition of the gas mix. The permeability ratio (β) varied from 0.73 ± 0.01 to 1.34 ± 0.01. A mathematical model considering the co-current effect of CO₂ flux on the gas exchange rate for O₂ was developed. These results suggest that there is a significant drag effect in the gas exchange process that should be taken into consideration when designing perforation-mediated MAP.     

The effect of modified atmosphere packaging on the microbiological,physical, chemical and sensory characteristics of broadtail squid (Illex coindetii)

The aim of this work was to evaluate the effect of various atmosphere compositions (20% CO₂/80% N₂ for modified atmosphere packaging (MAP) 1, 50% CO₂/50% N₂ for MAP 2, 70% CO₂/30% N₂ for MAP 3 and vacuum packaging) on the microbial (mesophiles, psychrophiles, Pseudomonas spp., Brochothrix thermosphacta and Enterobacteriaceae), physical, chemical [trimethylamine (TMA) and total volatile basic nitrogen (TVBN)] and sensorial characteristics of broadtail squid (Illex coindetii) stored for 10 days at 2 ± 1 °C. All microbial populations were severely restrained by MAP 3 with the exception of Enterobacteriaceae, which seemed to take advantage of the lack of competitive microflora and had enhanced microbial counts on MAP samples (P < 0.05). Colour attributes were better maintained on MAP‐stored samples. Drip loss was less on vacuum‐packaged squids. MAP 2 was the best atmosphere for the preservation of tissue consistency. TMA and TVBN formation was limited by high CO₂ atmospheres, even though both elevated in all studied conditions. Shelf life based on sensory characteristics was determined to be 10, 8, 6, 6 and 4 days for MAP 3, MAP 2, MAP 1, vacuum and control samples, respectively.     

Thymol and modified atmosphere packaging to control microbiological spoilage in packed fresh cod hamburgers

A study on the use of mild technologies to produce packaged fish hamburgers was presented. In particular, the antimicrobial effect of some natural compounds (carvacrol, eugenol, thymol, green tea extract, rosemary extract, grapefruit seed extract and lemon extract), at various concentrations (500–10 000 ppm), was screened in vitro against the main fish spoilage micro‐organisms (Shewanella putrefaciens and Photobacterium phosphoreum). Lemon extract and thymol, in combination with modified atmosphere packaging, showed the greatest inhibition activity, therefore, thymol was subsequently used as an ingredient for producing fish hamburgers. Results pointed out that this combination is effective in controlling the growth of microbial species mainly involved in fresh fish spoilage; in particular, it significantly (P < 0.05) reduced the growth rate of bacterial population, performing about 4.8 log CFU g^?1 and 6.5 log CFU g^?1 reduction of the hydrogen sulphide producing bacteria and psychrotrophic aerobic specific spoilage organisms cell load, respectively, if compared with the control.     

Effect of muscle,ageing time and modified atmosphere packaging conditions on the colour,oxidative and microbiological stability of packed beef

The objective of this study was to evaluate the influence of two different vacuum ageing times (7 and 14 days) and the impact of the modified atmosphere packaging (MAP) configuration (gas/product ratios: 0.5 and 1 and gas composition: 70% O₂ + 30% CO₂ and 40% O₂ + 30% CO₂ + 30% N₂) on the quality of fresh beef during subsequent storage at 4 °C. For this purpose, three separate experiments were performed. For each experiment, two different muscles (Longissimus dorsi and Biceps femoris) were sampled from four double‐muscled Belgian Blue beef carcasses. Next to colour, also the evolution in microbial load, pH, O₂ and CO₂ in the headspace and lipid oxidation at the meat surface were evaluated. A vacuum ageing for 14 days compared with 7 days resulted in a higher initial microbial load on the day of MAP packaging, which resulted finally in a significantly shorter shelf life. This ageing effect was less pronounced on the colour stability and lipid oxidation of the meat samples. No significant influence of the packaging configuration on any of the analysed parameters (colour, microbial load, pH and lipid oxidation at the meat surface) was observed.     

Effects of water extract of Urtica dioica L. and modified atmosphere packaging on the shelf life of ground beef

Effects of lyophilized Urtica dioica L. water extract (LUWE) and modified atmosphere packaging (MAP) on the quality and shelf life of ground beef were investigated. Ground beef was stored as aerobic control, MAP (80%O₂ + 20% CO₂), MAP + 250 ppm LUWE and MAP and 500 ppm LUWE at 2 ± 0.5 °C for 14 days. MAP and LUWE had significant effects on mesophilic, psychrotrophic and lactic acid bacteria and Pseudomonas counts. Depending on the level of LUWE, Pseudomonas and psychrotrophic counts decreased. Treatment with 500 ppm LUWE + MAP showed the lowest TBARS values compared to other groups during storage. 80% O₂-MAP increased TBARS values. Treatment had no significant effect on L* and b* values of the exterior of the ground beef, but had significant effects on the color of interior sections.     

Combined effects of a natural Allium spp. extract and modified atmospheres packaging on shelf life extension of olive‐based paste

This study aimed to extend the shelf life of non‐thermally stabilised olive‐based paste by adding different concentrations (0.2, 0.5, 1.0 g kg^?1) of a natural Allium spp. extract and/or by using different packaging atmospheres (MAP1, 75% Ar‐23% CO₂‐2% H₂; MAP2, 70% N₂‐30% CO₂) during refrigerated storage. Higher amounts of the natural extract gave the highest level of microbial inhibition, increased hardness, a greater release of aldehydes, esters, and ketones, and a better colour preservation when used with MAP1. The natural extract and MAP, either alone or in combination, produced no sensory defects (except for the control in MAP2), but a greater loss of typical olive flavour. The addition of the natural extract used with an appropriate MAP, can retain the quality attributes and extend shelf life for approximately 14 days longer than the control (without natural extract and MAP), and a better performance is achieved by using greater amounts of natural extract and MAP1.