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.     

Shelf-stability enhancement of precooked red claw crayfish (Cherax quadricarinatus) tails by modified CO2/O2/N2 gas packaging

Three types of packaging systems were compared for their influence on the storage stability (2 °C) of precooked and peeled red claw crayfish tails. Modified atmosphere packaging (MAP; with 80%CO₂/10%O₂/10%N₂) almost totally inhibited the growth of aerobic bacteria and coliforms when compared with aerobic polyvinylchloride packaging (PVCP) and vacuum packaging (VP). MAP also prevented a pH rise, purge loss, and texture toughening or softening of stored red claw when compared with PVCP or VP (P<0.05). Lipid oxidation was minimal in all three packaging systems. Thus, MAP offers an attractive means to preserve the shelf life of precooked red claw stored under refrigerated retail display conditions.     

Effect of reduced oxygen atmosphere and sodium acetate treatment on the microbial quality changes of seer fish (Scomberomorus commerson) steaks stored in ice

The effect of reduced oxygen atmosphere and sodium acetate treatment on the microbial quality of seer fish (Scomberomorus commerson) steaks was determined during chilled storage (1–2 °C). The O₂ absorber reduced the oxygen content in the pack to less than 0.01% corresponding to 99.96% reduction within 24 h. The use of O₂ absorber with sodium acetate dip treatment (2% w/v) extended the sensory shelf life up to 25 days compared to only 12 days for control air packs and 20 days for untreated samples with O₂ absorber. A prominent lag phase was observed for many bacterium studied, particularly for the sodium acetate treated samples with O₂ absorber. On the day of sensory rejection, both the total mesophilic and psychrotrophic counts reached 7.7–8.1 and 7.1–7.9 log cfu/g, respectively. The sodium acetate treatment and reduced O₂ atmosphere affected the type of major spoilers. In air packed samples, H₂S-producers predominated followed by Brochothrix thermosphacta, Pseudomonas spp., where as in the untreated samples with O₂ absorber, H₂S-producers predominated the microbial flora followed by Lactobacillus spp. For treated samples with O₂ absorber, B. thermosphacta formed the major micro-flora followed by Lactobacillus spp. The use of O₂ absorber inhibited the growth of Pseudomonas spp., and total Enterobacteriaceae.     

Effect of CO2 dissolution on the shelf life of ready-to-eat Octopus vulgaris

Due to the increasing commercial importance of octopus (Octopus vulgaris) and the growing demand for convenient and ready-to-eat products, soluble gas solubilisation (SGS), a relatively recent methodology of active packaging proposed to extend the shelf life of packaged fish, was tested. The effect on cooked octopus of CO₂ dissolution applied in a 2 bar saturated atmosphere for 30 min was followed by sensory, microbiological and physical/chemical quality parameters of vacuum packed products during chilled (3 °C ± 0.5 °C) and abuse temperature (24 °C ± 0.5 °C) storage for 28 days and 48 h, respectively. The SGS pre-treatment of cooked octopus with CO₂ had a positive effect on the delay of the microbial growth during chilled storage. On the other hand, during the acceptability period TMA-N and TVB-N showed similar changes during storage period and were not affected by the CO₂ treatment. Oxidation of cooked octopus did not appear to be a significant problem during chilled storage. Sensory shelf life was estimated as 10 days and 12 h in chilled and abuse temperature storage, respectively and no significant extension was visible as a function of SGS treatment. Though not enough per se to increase the shelf life of cooked octopus, the use of SGS by the food industry as a hurdle technology component with bacteriostatic effect is a valuable tool to allow an effective extension of the period of use-by date.

Industrial relevance

Common octopus (Octopus vulgaris) is a highly appreciated marine species which requires at home a cooking step that entails some expertise, in order to attain the correct sensory quality, namely suitable tenderness. Supply of ready-to-eat products that offer healthy, tasty and fast meal solutions and that solves the problem of home preparation of octopus is of particular industrial relevance and stresses the need for new ways of marketing this species, other than in the fresh state. The current study aimed to develop a new seafood product that can be introduced in the market as fresh cooked octopus in a convenient package under vacuum, either as a ready-made meal or as a ready-to-be used product, to be further processed in more elaborated food preparations. To our knowledge no such product exists in the market and this is the first study dedicated to the evaluation of the shelf life of such a product and to a new active packaging technology that can extend the use-by date. Though not enough per se to increase the shelf life of cooked octopus, it is demonstrated that utilisation of CO₂ by the food industry, as a hurdle technology component with bacteriostatic effect under the conditions proposed, is a valuable tool to allow an effective extension of the period of use-by date.     

Supercritical CO2 extraction of γ-linolenic acid and other lipids from Arthrospira (Spirulina)maxima: Comparison with organic solvent extraction

Freeze-dried biomass of Arthrospira maxima Setchell & Gardner was submitted to supercritical CO₂ extraction using a flow type apparatus at a temperature of 50 °C and a pressure of 250 bar.     

Effect of suboptimal temperatures and sublethal CO2 levels on multiplication of Tribolium castaneum (Coleoptera: Tenebrionidae), alone or competing with Cryptolestes ferrugineus (Coleoptera: Cucujidae)

Groups of adults of Tribolium castaneum alone, or in combination with adults of Cryptolestes ferrugineus, were exposed to suboptimal temperatures (15°C, 20°C, and 25°C) and sublethal CO₂ levels (2%, 5%, and 10%) in dry (12%, wet mass basis) and damp (15%, wet mass basis) stored wheat in the laboratory, to investigate effects on population size. The mean adult numbers in single- and mixed-species tests were positively correlated with higher temperature and moisture content and negatively correlated with higher CO₂ levels. Adult numbers in single- and mixed-species tests were lower at sublethal CO₂ levels compared to ambient CO₂ levels at all the test temperatures and decreased in dry grain compared to damp grain. Although, a specific trend was not observed in population inhibition between mixed-species and single-species tests, overall the adult populations of T. castaneum were reduced in the presence of C. ferrugineus. A mathematical model was derived to predict the size of adult populations of T. castaneum alone, or in the presence of C. ferrugineus considering all the variables in this study. The model had an R² value of 0.72 but needs to be validated and refined with field data.     

Storage of olives (Olea europaea) under CO2 atmosphere: Effect on anthocyanins,phenolics, sensory attributes and in vitro antioxidant properties

Green, unripe olives were subjected to post-harvest treatment under a CO₂ atmosphere for a period of 12 days. The total polyphenol (TP), total flavonoid (TFd) and total anthocyanin (TA) contents, along with the antioxidant and sensory characteristics, were continuously monitored during the treatment on a 24 h-interval basis, in order to identify possible changes in the quality of olives related mainly to changes in the polyphenolic contents. The storage of olives under CO₂ atmosphere resulted in pronounced increases in TP and TF contents, mainly within the first 3-5 days, but TA exhibited a different pattern of evolution. Furthermore, storage under CO₂ contributed to flavour appearance with the development of fruity/floral notes, and reduced bitterness. The in vitro antioxidant properties of the CO₂-treated sample showed notable increases compared with the sample stored under regular atmospheric conditions. It was concluded that storage of olives under a CO₂ atmosphere resulted in the appearance of desired sensory attributes, by decreasing bitterness and developing aroma and colour, and the functional (antioxidant) properties were improved. This approach may be used as an alternative, chemical-free means of table olive debittering.     

Effects of alkali neutralization with CO2 on fermentation, chemical parameters and sensory characteristics in Spanish-style green olives (Olea europaea L.)

This paper aimed to study CO₂ use as alkali neutralizing agent instead of the traditional washings with water, in Spanish-style green olives. Titratable acidity, pH, sugars and microbial populations were monitored during processing. CO₂ treatment was effective in reducing water-soluble carbohydrate loss from the olives during washing step and affected combined acidity and lactic acid fermentation. The final pH of the fermented brine was higher than in control, mainly due to high buffering capacity of the solution. CO₂ treatment allowed the reduction of more than 80% of the wastewaters. Sensory evaluations of the end product were carried out. Olives treated with CO₂ were perceived to be more intense in acidic taste than control, while for texture attributes no differences were detected.     

Low field Nuclear Magnetic Resonance on the effect of salt and modified atmosphere packaging on cod (Gadus morhua) during superchilled storage

Low field Nuclear Magnetic Resonance was used to evaluate the effect of salt and modified atmosphere packaging (MAP) on cod loins during superchilled storage. Transversal and longitudinal proton relaxation times of the cod loins were measured with Carr-Purcell-Meiboom-Gill (CPMG) and Inversion Recovery (IR) pulse sequences respectively. The relaxation parameters reflected the observed differences in the muscle caused by variation in salt concentration, the choice of salting method (brining or brine injection) and packaging (air or MAP), as well as superchilled storage temperature and storage time. Significant correlations were found between the NMR parameters and parameters describing the water dynamics of the muscle (moisture and salt content, water holding capacity, drip and cooking yield), as well as muscle pH and counts of H₂S-producing bacteria in chosen sample groups. The study showed the possibility of using low field NMR to indicate fish quality deterioration, when the spoilage mechanisms affect the water properties and muscle structure.     

Determination of hyperin in seed of Cuscuta chinensis Lam. by enhanced chemiluminescence of CdTe quantum dots on calcein/K3Fe(CN)6 system

In this paper, 3-mercaptocarboxylic acid (MPA) modified CdTe quantum dots (QDs) were used as sensitizers, to enhance the chemiluminescence (CL) of the calcein/K₃Fe(CN)₆ system. A new CL system of CdTe/calcein/K₃Fe(CN)₆ was developed. The effects of reactant concentrations and the particle sizes of CdTe QDs on the CL emission were investigated in detail. The possible enhancement mechanism of the CL was also further investigated based on the photoluminescence (PL) and CL spectra. Polyphenols such as chlorogenic acid, quercetin, hyperin, catechin and kaempferol, were observed to inhibit the CL signal of the CdTe/calcein/K₃Fe(CN)₆ system and determined by the proposed method. The proposed method was applied to the determination of hyperin in seed of Cuscuta chinensis Lam. and the results obtained were satisfactory.     

Inactivation of different strains of Escherichia coli O157:H7 in various apple ciders treated with dimethyl dicarbonate (DMDC) and sulfur dioxide (SO2) as an alternative method

Escherichia coli has been identified as the causative agent in numerous foodborne illness outbreaks associated with the consumption of fresh apple cider. Apple cider has a pH which is normally below 4.0 and would not be considered a medium capable of supporting the growth of foodborne pathogens. The association of unpasteurized apple cider with foodborne illness due to E. coli O157:H7 has however, led to increased interest in potential alternative methods to produce pathogen free cider. Apple cider was prepared from eight different apple cultivars, inoculated with approximately 10⁶–10⁷ CFU of three strains of E. coli O157:H7 per ml (933, ATCC 43889, and ATCC 43895) and tested to determine the effectiveness of sulfur dioxide (SO₂) and dimethyl dicarbonate (DMDC). Bacterial populations for treated and untreated samples were then enumerated by using non-selective media. Eight different ciders were treated with DMDC (125 and 250 ppm) and SO₂ (25, 50, 75, 100 ppm). Greater than a 5-log reduction was achieved at room temperature with 250 ppm of DMDC and 50 ppm of SO₂ after the incubation time of 6 h and 24 h, respectively. Addition of DMDC and/or SO₂ may offer an inexpensive alternative to thermal pasteurization for the production of safe apple cider for small apple cider producers.