Residual effect of CO2 on hake (Merluccius merluccius L.) stored in modified and controlled atmospheres

 The residual effect of CO₂ on whole gutted hake kept with three different CO₂/O₂/N₂ gas mixtures: 60/15/25, 80/20/0 and 40/40/20, and two different kinds of atmospheres (controlled and modified) during 12 days followed by conventional storage in ice for up to 30 days was examined by physical, chemical and sensory analyses. Shelf life was longer in lots kept in atmospheres than in control lots and was further prolonged by controlled than by modified atmospheres. The lots kept in the atmosphere with the highest concentrations (80%) of CO₂ exhibited the lowest trimethylamine nitrogen and total volatile basic nitrogen values. However, these were also the lots that scored worst in sensory analysis. The lots that scored best in sensory analysis were those which were kept in the gas mixtures with 60% and 40% of CO₂. Oxidative rancidity was not a problem in the samples stored in the atmosphere with 40% O₂; Thiobarbituric acid levels were lower than 2 mg/100 g in all lots throughout storage, and the assessors detected no rancidity. The residual effect of CO₂ on whole gutted hake was more effective in controlled atmosphere lots. Received: 15 June 2000 / Revised version: 17 August 2000     

Effect of CO<Subscript>2</Subscript>/O<Subscript>2</Subscript>-containing modified atmospheres on packed deepwater pink shrimp (<Emphasis Type="Italic">Parapenaeus longirostris</Emphasis>)

The purpose of this study was to analyse the effect of two gas mixtures, containing 40% CO₂/30% O₂/30% N₂ and 45% CO₂/5% O₂/50% N₂, on the microbiological flora (total bacteria count, H₂S-producers microorganisms and enterobacteria) and some biochemical indexes (trimethylamine, total volatile basic nitrogen and biogenic amines) of chilled shrimp. Modified atmosphere packaging (MAP) on shrimps delayed the microbial growth compared to air-packed or iced stored shrimp as well as the trimethylamine and total volatile nitrogen production. However, the production of some biogenic amines seemed to be enhanced during the storage of MAP-shrimp.     

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.     

Microbiological,chemical and sensory assessment of mussels (<Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis>) stored under modified atmosphere packaging

Wild mussels (Mytilus galloprovincialis), were packaged aerobically under vaccum packaging(VP) and modified atmosphere packaging (MAP (50%/50% CO₂/N₂: M1, 80%/20% CO₂/N₂: M2, 65%/35% CO₂/N₂: M3), and stored at 2 ± 1 °C. Quality evaluation was carried out using microbiological, chemical and sensory analyses. Microbiological results revealed that M2 and M3 delayed microbial growth compared to M1. Of the chemical indices determined, the TVB-N and TMA-N values of M2 remained lower than the proposed acceptability limits of 35 mg N/100 g and 8 mg N/100 g, respectively, up to 8 days of storage. All of the MAP and VP mussel samples exceeded these limits after 12 days of storage. All samples retained desirable sensory characteristics during the first 8 days of storage. Based on microbiological and chemical analyses along with sensory evaluation, M2 and M3 gave a longer shelf-life compared with VP and M1. M2 gas mixture was the most effective for mussel preservation.     

Development of CO<Subscript>2</Subscript>-Mediated Switchable Hydrophilicity Solvent-Based Microextraction Combined with HPLC-UV for the Determination of Bisphenols in Foods and Drinks

In traditional dispersive liquid-liquid microextraction procedures, both extraction and dispersive solvents are required, and thus, it increases the consumption of organic solvent. Herein, we reported a CO₂-mediated switchable hydrophilicity solvent-based microextraction (SHS-BME) for the determination of bisphenol compounds (BPCs) in complex milk and drink samples. N,N-Dimethylcyclohexylamine was used as a switchable hydrophilicity solvent; it can switch reversibly between one form that is miscible with water and another that forms a biphasic mixture with water, and thus allow extraction of the analytes in a homogeneous phase without dispersive solvent. Several important parameters were screened and optimized by single factor experiments and central composite design as follows: 782 μL of switchable solvent, 375 μL of NaOH solvent, and 1.1:1 switchable solvent/water (v/v). Under the optimized SHS-BME conditions, the limit of detections (LODs) for BPCs in milk, orange juice, and energy drink samples were in the range of 0.27–0.40 μg L^?1 for BPE, 0.17–0.30 μg L^?1 for BPA, and 0.50–0.67 μg L^?1 for BPB, respectively, and the extraction recoveries for BPCs were in the range of 79.5–103.4% in milk, of 84.5–97.5% in orange juice, and of 91.9–101.2% in energy drinks. The precision of the method, based on relative standard deviations (RSDs), ranged from 1.7 to 4.8% and from 2.1 to 5.7% for intra-day and inter-day comparisons, respectively. In total, this SHS-BME method possesses many advantages, such as high extraction recovery and high detection sensitivity (low LODs and RSDs), no requirement of dispersive solvent, simple operational procedure, reducing the pretreatment time and workload, and so on. Therefore, it has a great potential application value for detection of trace BPCs in routine food tests.     

A comparative study of flavonoid contents and antioxidant activities of supercritical CO<Subscript>2</Subscript> extracted pine barks grown in different regions of Turkey and Germany

Utilization of renewable resources is gaining more emphasis and large quantities of solid wastes are produced by the forestry industry. However, there is a significant lack of transformation of such wastes into potentially novel products. The barks of various Pinus species from different regions of Turkey (P. pinea, P. sylvestris, P. nigra) and Germany (P. parviflora, P. ponderosa, P. sylvestris, P. nigra) were extracted by supercritical CO₂ extraction. Different sources of variability including location and species were evaluated for their active constituents, (−)-catechin, (−)-epiatechin, (−)-catechin gallate, and taxifolin, applying HPLC, radical scavenging activities (RSA), and total phenol analysis. The total amounts of flavan-3-ols (9.916 mg/g) were the highest in P. pinea extract harvested from Aydin, having the hottest climate and longest duration of sun (P < 0.01). In addition, P. pinea had the highest RSA (81.0 %) and total phenol value (83.0 mg GAE/g).