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Chemical Indicators (chemical + indicator)
Selected AbstractsStream macroinvertebrate occurrence along gradients in organic pollution and eutrophicationFRESHWATER BIOLOGY, Issue 7 2010NIKOLAI FRIBERG Summary 1.,We analysed a large number of concurrent samples of macroinvertebrate communities and chemical indicators of eutrophication and organic pollution [total-P, total-N, NH4,N, biological oxygen demand (BOD5)] from 594 Danish stream sites. Samples were taken over an 11-year time span as part of the Danish monitoring programme on the aquatic environment. Macroinvertebrate communities were sampled in spring using a standardised kick-sampling procedure whereas chemical variables were sampled six to 24 times per year per site. Habitat variables were assessed once when macroinvertebrates were sampled. 2.,The plecopteran Leuctra showed a significant negative exponential relationship (r2 = 0.90) with BOD5 and occurred at only 16% of the sites with BOD5 above 1.6 mg L,1. Sharp declines with increasing BOD5 levels were found for the trichopteran families Sericostomatidae and Glossosomatidae although they appeared to be slightly less sensitive than Leuctra. Other plecopterans such as Isoperla showed a similar type of response curve to Leuctra (negative exponential) but occurred at sites with relatively high concentrations of BOD5 up to 3,4 mg L,1. In contrast, the response curve of the isopod Asellus aquaticus followed a saturation function reaching a plateau above 3,4 mg L,1 BOD5 and the dipteran Chironomus showed an exponential increase in occurrence with increasing BOD5 concentration. 3.,Macroinvertebrate occurrence appeared to be related primarily to concentrations of BOD5, NH4,N and total-P whereas there were almost no relationships to total-N. Occurrence of a number of taxa showed a stronger relationship to habitat conditions (width and substrate) than chemical variables. 4.,Important macroinvertebrate taxa are reduced at concentrations of BOD5 that are normally perceived as indicating unimpacted stream site conditions. Our results confirmed sensitivity/tolerance patterns used by existing bioassessment systems only to some degree. [source] Ecophysiological attributes of a Lactobacillus sp. and a Pseudomonas sp. on sterile beef fillets in relation to storage temperature and film permeabilityJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2001E. Tsigarida Aims:,To determine the combined effect of packaging film and temperature on the rate and type of end-products caused by the growth of two main contrasting prevailing organisms in air and 100% CO2, Pseudomonas sp. and Lactobacillus sp., respectively. Methods and Results:,Pseudomonas sp. and Lactobacillus sp. were inoculated individually on sterile meat fillets. The samples were packed in air or 100% CO2, using a high and a low permeable film, and stored at 0 and 10°C. Pseudomonas sp. grew aerobically and in 100% CO2 using high permeable film at both storage temperatures, while film permeability significantly affected the growth of Lactobacillus sp. only at 10°C. Enzymatic kits and HPLC and GC analysis were used to determine the chemical changes of the samples throughout storage. Pseudomonas sp. presented a greater rate of consumption of glucose and lactate than Lactobacillus sp. in samples stored aerobically or with high permeable film. Propanol-1 and two unidentified organic acids were present only in samples inoculated with Pseudomonas sp., while acetaldehyde, ethanol, diacetyl and acetoin were detected in samples inoculated with Lactobacillus sp. Conclusions:,Since different microbial species and introduction of new packaging methods affect spoilage reactions of meat either qualitatively or quantitatively, a combination of several chemical indicators should be thoroughly investigated. Significance and Impact of the Study:,The present study provides information on how and when such potential indicators can be exploited for the benefit of the industry and consumer. [source] Cod and rainbow trout as freeze,chilled meal elementsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2010Louise H S Jensen Abstract BACKGROUND: ,Meal elements' are elements of a meal, e.g. portions of pre-fried meat, sauces, frozen fish or pre-processed vegetables typically prepared industrially. The meal elements are distributed to professional satellite kitchens, where the staff can combine them into complete meals. Freeze,chilling is a process consisting of freezing and frozen storage followed by thawing and chilled storage. Combining the two would enable the manufacturer to produce large quantities of frozen meal elements to be released into the chill chain according to demand. We have studied the influence of freeze,chilling on the quality attributes of cod and rainbow trout portions. Sensory profiling and chemical analyses were used to determine the changes in quality after slow thawing and subsequent chill storage and to find the high-quality shelf life. RESULTS: Cod had a consistent and high sensory quality during the first 6 days of chilled storage, and the corresponding time for rainbow trout was 10 days. After this period the sensory quality decreased and chemical indicators of spoilage were seen to increase. CONCLUSION: The consistent quality during storage and the high-quality shelf life are practically applicable and cod and rainbow trout seem potential candidates for freeze,chilled meal elements. Copyright © 2009 Society of Chemical Industry [source] Chemical and sensory stability of roasted high-oleic peanuts from ArgentinaJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2006Valeria Nepote Abstract The purpose of this work was to determine the chemical and sensory stability of roasted peanuts prepared with a high-oleic cultivar, Granoleico (GO-RP), in comparison to a regular cultivar, Tegua (T-RP), from Argentina. Consumer test of fresh products, oxidative stability estimated by chemical indicators (peroxide and p -anisidine values, conjugated dienes and trienes) and descriptive analyses during storage (at 23 and 40 °C) were performed on the roasted peanuts. GO-RP did not differ from T-RP as regards consumer acceptance. Chemical indicator values and oxidized and cardboard flavors showed lower increments for GO-RP than T-RP during storage. Roasted peanutty flavor decreased for both samples at 23 and 40 °C. Using prediction equations, roasted peanuts prepared with kernels of high-oleic contents had shelf lives of 25 (at 23 °C) and 10 (at 40 °C) times longer than those elaborated with normal peanuts. Copyright © 2006 Society of Chemical Industry [source] Microbiological, chemical and sensory changes of whole and filleted Mediterranean aquacultured sea bass (Dicentrarchus labrax) stored in iceJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2003Dimitra Taliadourou Abstract The effect of filleting on the microbiological, chemical and sensory properties of aquacultured sea bass (Dicentrarchus labrax) stored in ice was studied. Pseudomonads, H2S-producing bacteria (including Shewanella putrefaciens) and Brochothrix thermosphacta were the dominant bacteria at the end of the 16 day storage period in ice for both whole ungutted and filleted sea bass. Enterobacteriaceae were also found in the spoilage microflora of whole ungutted and filleted sea bass, but their counts were always lower than those of pseudomonads, H2S-producing bacteria (including S putrefaciens) and B thermosphacta. Total viable counts for whole ungutted sea bass were always lower than those for filleted sea bass samples. Of the chemical indicators of spoilage, TMA (trimethylamine) values of whole ungutted sea bass increased very slowly, whereas significantly higher values were obtained for filleted samples, with respective values of 0.253 and 1.515 mg N per 100 g muscle being reached at the end of their shelf-life (days 13 and 9 respectively). TVB-N (total volatile basic nitrogen) values showed a slight increase for whole ungutted sea bass during storage, reaching a value of 26.77 mg N per 100 g muscle (day 13), whereas for filleted fish a corresponding value of 26.88 mg N per 100 g muscle was recorded (day 9). TBA (thiobarbituric acid) values increased slowly for whole ungutted and filleted sea bass samples throughout the entire storage period, reaching final values of 4.48 (day 13) and 13.84 (day 9) mg malonaldehyde kg,1 respectively. Sensory assessment of raw fish using the EC freshness scale gave a grade E for up to 5 days for whole ungutted sea bass, a grade A for a further 4 days and a grade B for an additional 4 days, after which sea bass was graded as C (unfit). Overall acceptability scores for odour, taste and texture of cooked whole ungutted and filleted sea bass decreased with increasing time of storage. The results of this study indicate that the shelf-life of sea bass stored in ice, as determined by overall acceptability sensory scores and microbiological data, is 8,9 days for filleted and 12,13 days for whole ungutted fish. Copyright © 2003 Society of Chemical Industry [source] | ||||||||||