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.     

Production of volatile compounds in the fermentation of chardonnay musts inoculated with two strains of Saccharomyces cerevisiae with different nitrogen demands

This paper studies the behaviour of two strains of Saccharomyces cerevisiae with different nitrogen requirements in the production of esters and higher alcohols during alcoholic fermentation. To carry out the study a chardonnay must with a high content of nitrogen compounds was used. The results showed that the strain with the highest nitrogen demand produced a higher concentration of esters during fermentation and gave rise to a wine with a somewhat lesser content of higher alcohols. The formation of volatile compounds was probably related to the consumption of nitrogen by the strains as the nitrogen nutrients act as precursors in the synthesis of esters and alcohols and regulate their production.     

Effect of nisin on the storage of sous vide processed Korean seasoned beef

Seasoned beef called Jangzorim in Korea is produced by boiling in soy sauce, and is a popular food in Korea. The aim of this study is to evaluate the microbial safety and physical qualities of sous vide processed seasoned beef, and the effect of nisin during storage. Sous vide processed packages with or without nisin (100 IU or 500 IU) were stored at 4 °C or 25 °C for 60 days, and samples measured for quality at regular intervals throughout this storage period. In the case of 25 °C storage, the number of mesophilic microorganisms in seasoned beef packages without nisin increased markedly, but with nisin there was no observed increase. Psychrotrophic microorganisms, anaerobic microorganisms, and B. cereus cells showed similar trends, although C. perfringens was not detected in all samples. At 25 °C storage, changes in the cutting force of packages containing nisin showed no significant change, packages without nisin decreased markedly. The colour of packages without nisin showed a drastic decrease in lightness (‘L’) while no changes were observed in packages with nisin.     

Protease activity of Oenococcus oeni viable cells on red wine nitrogenous macromolecular fraction in presence of SO2 and ethanol

The protease activity of Oenococcus oeni X₂L viable cells on red wine nitrogenous macromolecular fraction (NMF) as sole nitrogen source was determined. The enzyme releases growth factors for Oenococcus oeni. In presence of SO₂ and ethanol the rate of amino acids liberation was twofold higher. A peptide peak analyzed by HPLC with a retention time of 47 min diminishes markedly during the first 2 h incubation. O. oeni X₂L living cells are able to produce the exoprotease and to act on the red wine NMF in the presence of SO₂ and ethanol releasing essential amino acids for its survival.     

Characterization of Mediterranean mussels (Mytilus galloprovincialis) harvested in Adriatic Sea (Italy)

The aim of this work was to analyse some quality parameters of Mytilus galloprovicialis harvested monthly in the period ranging from April 2002 and February 2003 in a longline off-shore mussel farm, located in the Adriatic Sea, near Cattolica (Emilia Romagna Region, Italy). After harvesting, the samples were analysed in order to determine the counts of fecal coliforms (FC) and Escherichia coli, the presence of Salmonella, as prescribed by Italian and European Community regulations, and other pathogens (Vibrio parahaemolyticus, Listeria monocytogenes), as well as the meat yield and its proximate composition, its Fe, Cr, Cd, Zn, Pb and Cu content, the total lipids of the meat and their specific composition. The results obtained evidenced that many of the parameters studied, i.e. the meat proximate composition, the lipid fatty acid composition and the microbiological indices, were subjected to seasonal fluctuations. In particular, the microbiological data showed that 4 mussel samples (June, December, January and February) out of 12 did not match the limit imposed by Italian law and Emilia Romagna protocol concerning the FC and E. coli counts. While L. monocytogenes and Salmonella spp. were never detected in all the samples analysed, three samples (April, January and February) were positive for the presence of V. parahaemolyticus. No seasonal fluctuations were evidenced for Fe, Cr, Cd, Zn, Pb and Cu contents, always under the limits imposed by Italian law.     

利用泰勒级数展开的振幅谱积分差值的Q值估计方法

品质因子Q是地震数据处理和解释中的一个重要参数,可用于提高地震记录纵向分辨率和反映储层特性。在常规Q值估计中,时窗与带宽选择是Q值估计的关键,且噪声干扰也会对Q值估计产生影响。为此,文中提出一种基于泰勒级数展开的振幅谱积分差值方法(ASID)。该方法对振幅衰减项进行二阶泰勒级数展开,利用不同时刻地震子波振幅谱差值建立含有Q值的方程,通过求解方程获取Q值。对比试验表明,相对于常用的对数谱比法(LSR)、中心频移法(CFS)和对数谱面积差法(LSAD),文中所提方法具有受频带宽度和时窗宽度影响小,以及抗干扰能力强的优点,且更适用于含薄层地震记录的Q值估计。此外,将ASID法应用于实际海洋资料的CMP道集中,所得Q值估计结果与LSAD法具有良好的一致性。     

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.     

Quality deterioration of phane, the edible caterpillar of an emperor moth Imbrasia belina

The cause for the deterioration of quality in phane, the edible larva of the emperor moth, Imbrasia belina (Westwood) was investigated. Samples were subjected to bacteriological and mycological analyses. In addition insect pests which affect storage life of the product were also assessed. 70% of the bacterial isolates associated with phane were proteolytic and 75% were either chitinolytic, lipolytic or both. Most isolates were sporeformers. But, other Gram-positive and negative isolates were also present in significant numbers. The most frequent fungal isolates were species of Aspergillus, Penicillium, Fusarium, Cladosporium and phycomycetes. Some of the fungal isolates are known to be mycotoxin producers. The insect which were associated with phane were Dermestes maculatus, Sitophilus zeamais, Corcyra cephalonica, Tribolium confusum, Tribolium casteneum, Oryzaephilus surinamensis, Bracon hebetor, Anisopteromalus cavandrae, and Stathmopoda species. Mites were also found infesting stored phane. The postharvest deterioration of phane appeared to be a concerted effort by the bacteria, moulds and insects.     

Effect of high pressure processing on the quality of herring (Clupea harengus) and haddock (Melanogrammus aeglefinus) stored on ice

Fresh herring and haddock were vacuum-packed and subjected to high pressure processing (200, 250 and 300 MPa at 10 °C for both 1 and 3 min) or left untreated as controls. The samples were stored in ice at 2 °C for up to 14 days, during which time the changes in microbial quality, total volatile base nitrogen (TVBN) and trimethylamine (TMA) production were monitored. Microbial shelf-life was determined as the storage time required for psychrotrophic counts to reach 10⁶ CFU g^?1, while chemical shelf-life was estimated as the time taken for TVBN and TMA values to reach 35 mg N 100 g^?1 and 15 mg N 100 g^?1 respectively.High pressure significantly delayed microbial growth (p < 0.05) in both herring and haddock. In the case of herring the microbiological shelf-life was extended from ～4 days in controls to ?13 days in fish pressure-treated at 200 MPa/3 min. Microbial numbers in all the haddock samples tended to be lower throughout the storage period, compared to herring, irrespective of pressure treatment, and none of the pressure-treated samples reached unacceptable psychrotrophic numbers until 14 days in ice compared to 10 days in the controls. The microflora of both the control and pressure-treated herring and haddock at day 0 were predominantly Gram-positive cocci (Micrococcus spp. and Staphylococcus spp.) and spore-forming rods (Clostridium spp. and Bacillus spp.). This microflora did not change significantly during storage of the fish in ice at 2 °C for 10 days.Pressure treatment also delayed TVBN and TMA production in the fish. In the case of herring, predicted values did not reach unacceptable levels until at least 18 days (200 MPa/3 min) compared to 5.5 days in controls. With haddock, TMA and TVBN values in control samples reached unacceptable limits between 6 and 10 days of storage. However, the levels remained below the limits of acceptability in all pressure-treated samples during storage, apart from on day 14, when the TVBN value in samples treated at 200 MPa/1 min exceeded the level of acceptability.Overall, taking account of the various spoilage indicators, the minimum treatment required to increase shelf-life in herring and haddock to ～13 days on ice was found to be 200 MPa for 3 min.     

Microbiological profile of helva sold at retail markets in Izmir city and the survival of Staphylococcus aureus in this product

The objective of this research was to determine the microbiological profile of tahin helva, a low moisture confectionery. A total of 63 tahin helva samples were collected from the retail markets in Izmir, Turkey. These samples were examined by standard procedures for aerobic plate count (APC) and counts of moulds and yeasts, Enterobacteriaceae, Staphylococcus aureus and Salmonella spp. APC of samples ranged from <10 to 1.6 × 10⁵ cfu/g. The counts for moulds, yeasts and Enterobacteriaceae ranged from <10 to 1.8 × 10³, <10 to 7 × 10², <10 to 8.5 × 10² cfu/g, respectively. None of the samples contained S. aureus or Salmonella. The potential for survival of S. aureus in the product stored at refrigeration (4 °C) and room (20 °C) temperatures was evaluated by artificial contamination. S. aureus cells were still recovered after 9 months of storage at both temperatures. The results of this investigation indicate that S. aureus contamination of tahin helva, (a_w of 0.172) may constitute a potential public health hazard, depending on the extent of contamination and mishandled exercise at the sale area and the kitchen.     

Effect of tea polyphenols on the physical and chemical characteristics of dried-seasoned squid (Dosidicus gigas) during storage

The effects of tea polyphenols (TP) dip treatment on the physical and chemical characteristics of dried-seasoned squid (Dosidicus gigas) during storage at 25 °C were assessed. After the storage, the b* value increased significantly, while the free amino acids (FAA) including Ser, Gly, Arg, Tyr and Lys, and the dominant reducing sugar (RS), lactose, decreased remarkably, which revealed the occurrence of browning reaction in dried-seasoned squid. The progressive conversion of trimethylamine oxide (TMAO) and production of thiobarbituric acid (TBA) and total volatile basic nitrogen (TVB-N) were found during the entire period of storage. Furthermore, the advantages of reducing moisture loss, inhibiting oxidation of lipids, depressing TMAO breakdown and TVB-N accumulation were observed, while the browning reaction exhibited no significant decrease for the TP samples. These results indicated that the addition of TP could maintain quality of dried-seasoned squid.     

基于时变子波的品质因子估计

地下介质的地层滤波效应和吸收衰减效应会使地震信号频带变窄、主频降低、相位畸变。在对非稳态地震记录进行时变子波估计的基础上,从频率域和时间域两方面研究子波的时变性与品质因子的关系。首先推导非稳态记录正演模拟的时间域实现方法,通过子波褶积矩阵表达传播子波的时变性;其次,基于最优化思想,在给定范围内扫描Q值,使深部和浅部两个传播子波达到最佳匹配,提出了频率域子波匹配Q值估计方法和时间域子波匹配Q值估计方法。相比于常用的谱比法,频率域子波匹配法不需要做谱比,并通过最小二乘优化算法替代线性回归,具有更高的抗噪性。时间域子波匹配法通过子波褶积矩阵引入衰减响应,从根本上避免谱估计的误差,具有更高的精度。理论模型和实际数据计算结果表明,两种方法都能快速有效地估计品质因子,与时变子波谱比法相比,对低信噪比数据具有更强的鲁棒性。同时,模型测试表明品质因子估计结果的纵向分辨率有限,两个子波间的时间间隔制约着估计精度。     

Survival and growth of Listeria monocytogenes on sausage formulated with inoculated and stored rework product

To assess the effect of including contaminated rework on survival and growth of Listeria monocytogenes, two sausage formulations (one American, Bologna sausage; and one Bulgarian, Stranja sausage) were inoculated with the pathogen and stored for 4 days at 10 °C plus 15 h at 30 °C. After storage, both rework types were included (at 20% and 40%) in corresponding fresh sausage emulsions and heated to 68, 70 and 71.7 °C; fresh Bologna and Stranja emulsions served as controls and were inoculated with 24 h broth cultures of the same 10-strain mixture of L. monocytogenes and thermally treated to the same temperatures. The results showed that heating to 68 and 70 °C inactivated 3–4 log CFU/g of the initial concentration of L. monocytogenes cells (>7 log CFU/g), while heat treatment to 71.7 °C in the center of experimental samples reduced counts by 6 log CFU/g. Survival of L. monocytogenes in samples heated to 68 and 70 °C was higher in controls. Control samples of Stranja emulsion heated to 71.7 °C allowed higher growth (P < 0.05) during storage (5 days at 10 °C) as compared to other control and experimental rework samples. The Stranja emulsion had a higher fat content (20.2%) compared to the Bologna emulsion (11%). This study provides evidence about the possible danger when potentially contaminated rework is stored and then introduced into fresh product formulations.     

Elimination of Yersinia enterocolitica on carrots (Daucus carota L.) by using household sanitisers

In this study, the effects of lemon juice, the mixture of lemon juice–vinegar (1:1) and lemon dressing against Yersinia enterocolitica on carrot were investigated. Carrots inoculated with Y. enterocolitica cells (approximately 10⁶ cfu/ml) were treated with 100%, 75% and 50% lemon juice, a mixture of lemon juice–vinegar, and lemon dressing for 0, 15, 30 and 60 min. Enumeration of Y. enterocolitica populations on CIN agar beside TSA agar by using two methods as then performed. One hundred percent lemon juice was the most effective agent used, completely inhibiting viable cells of Y. enterocolitica on carrot after 15 min exposure. Although no growth was observed on carrots treated with 100% lemon juice for 15 min, there was no statistical difference between the antibacterial effects of 100% lemon juice, 75% lemon juice, the mixture of lemon juice–vinegar and lemon dressing whilst the effect of 50% lemon juice was statistically different from those solutions (P < 0.05) and its definite inhibitive activity was seen after 60 min treatment.     

Histamine production by Raoultella ornithinolytica in canned tuna meat at various storage temperatures

Canned tuna meat was inoculated with Raoultella ornithinolytica at a level of 2.0 log CFU/g (low) or 5.0 log CFU/g (high) and stored at 4, 15, 25, or 37 °C to investigate bacterial growth and formation of total volatile base nitrogen (TVBN) and histamine in canned tuna meat. R. ornithinolytica grew rapidly in all samples stored at temperature above 15 °C regardless of the inoculation levels. The histamine contents quickly increased to higher than 50 mg/100 g within 12 h in the low inoculated samples and stored at 37 °C as well as in those inoculated with the high level and stored at 25 °C or higher. However, growth of R. ornithinolytica and its histamine production were inhibited when samples were stored at 4 °C. The TVBN contents in all samples were all below 30 mg/100 g during storage even when the levels of histamine in some samples increased to greater than 50 mg/100 g. Therefore, canned tuna meat was a good substrate for histamine formation by bacterial histidine decarboxylation at elevated temperatures (> 15 °C) when it is contaminated with R. ornithinolytica.     

Occurrence of virulence factors and antibiotic resistances in Enterococcus faecalis and Enterococcus faecium collected from dairy and human samples in North Italy

The aim of this research was to study the incidence of potential virulence factors and antibiotic resistance in 38 Enterococcus faecalis and 43 Enterococcus faecium strains isolated from dairy products and human samples. The presence of the virulence factors agg, ace, esp, gelE, efaA and of the vanA and vanB genes was evaluated by PCR, while antibiotic resistance was tested by the disk diffusion method. Ent. faecalis displayed more virulence determinants than Ent. faecium, with the presence of multiple virulence traits. Virulence determinants were present in both human and dairy strains, while antibiotic resistance patterns of the two groups of strains were very different with a significant higher diffusion of resistances among human enterococci. Considering the results of our study, dairy enterococci cannot be considered the main potential source for dissemination of antibiotic resistances.     

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.     

Effect of SO2 on the formation and evolution of volatile compounds in wines

The aim of this work was to study the influence of SO₂ on the formation and later evolution of volatile compounds in wine bottles made from fermentations of sterilized and inoculated must. For this purpose, Parellada must, sterilized and inoculated with Saccharomyces cerevisiae, was fermented with and without SO₂. Subsequently, the obtained wines were aged in bottle during 6 months at room temperature with and without SO₂. The results show that SO₂ hardly had any effect on the formation of volatile compounds during fermentation. However, the wine stored in bottle with SO₂ showed a higher concentration of volatile compounds, mainly esters and alcohols, than the wine aged in bottle without SO₂.     

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.