Sensory properties Archives

Traditional skyr. Comparison of home-made and factory-made skyr - Pre-survey / Traditional skyr. Comparison between homemade and industrial produced skyr - Preliminary study

Post author By admin
Post date 01/05/2011

Published:

01/05/2011

Authors:

Þóra Valsdóttir, Eyjólfur Reynisson, Nadine Knocke, Aðalheiður Ólafsdóttir, Þórarinn E. Sveinsson

Supported by:

Agricultural Productivity Fund

Traditional skyr. Comparison of home-made and factory-made skyr - Pre-survey / Traditional skyr. Comparison between homemade and industrial produced skyr - Preliminary study

Skyr is one of the few Icelandic products that can truly be said to be traditional. The few studies that have been done on traditional, home-made skyr, date from the first half of the 20th century. This report presents a preliminary study of home-made and factory-produced skyrs, focusing on the assessment of sensory properties and the analysis of microbial flora using recent genetic methods. Significant differences were detected in sensory factors. The number of lactic acid bacteria and yeasts was considerably higher in home-made skyr. The same types of lactic acid bacteria were detected in different manufacturers and were the same as have been detected in previous studies. Yeasts of the same genus were found on both farms but not in factory-made skyr. Although these are the same bacterial species, it is possible that different phenotypes can be found between farms. Therefore, it would be interesting to investigate the possible metabolic or genotypic variability between strains from different production sites and their effect on the properties of skyr.

Skyr is one of few Icelandic products which can be stated as traditional. Little research has been executed on traditional skyr, of which most from the first part of the 20th century. In this preliminary study, homemade and industrial skyr is compared based on sensory properties and microbiological composition. Significant difference was found on several sensory attributes. Number of lactic acid bacteria and yeasts was much greater in homemade than industrial skyr. Same species of lactic acid bacteria were identified as in previous studies, however only some of previously identified yeast genera were found. Larger part of DNA needs to be sequenced and culture independent methods employed for a more specific identification. Such analysis could provide possibilities on establishing metabolic or genotype difference between different production locations.

Development of Quality Index Method and shelf life of thawed mackerel (Scomber scombrus) / Development of Quality Index Method and storage life of thawed mackerel (Scomber scombrus)

Post author By admin
Post date 01/07/2010

Published:

01/07/2010

Authors:

Kolbrún Sveinsdóttir, Patricia Miranda Alfama, Aðalheiður Ólafsdóttir, Emilía Martinsdóttir

Supported by:

AVS Fisheries Research Fund, UNU School of Fisheries, United Nations University

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Development of Quality Index Method and shelf life of thawed mackerel (Scomber scombrus) / Development of Quality Index Method and storage life of thawed mackerel (Scomber scombrus)

The QIM method (Quality Index Method) is an objective, fast and reliable sensory evaluation method that has been developed to assess the freshness of fish. The aim of the study was to prepare a QIM rating scale for thawed mackerel (Scomber scombrus) stored in ice at 0 ° C and to test its use in a shelf life test. The mackerel was evaluated by sensory evaluation according to QIM and DA method (generic descriptive analysis), microorganisms (TVC and H2S producing) were also counted and histamine was measured for up to 9 days after thawing. The result of the study was the QIM method for thawed mackerel which was developed and tested in a shelf life test. Quality factor - QI (total grade) increased linearly with ice shelf life. The QIM method for thawed mackerel is based on an assessment of quality factors such as the appearance of redness, texture, color and shape of the eyes, the color and odor of the gills, the appearance of mucus in the gill and gill leaf and the intestinal dissolution, and the total fish can reach a maximum of 19. The project also developed a method (general descriptive analysis-DA) for evaluating boiled mackerel. The main characteristics of the mackerel immediately after thawing were the smell and taste of fresh oil, the smell of metal and the sweet smell / taste that faded with the storage period. What limited the shelf life were sensory properties that describe the symptoms of damage, such as the stench and taste that can be noticeable in fatty fish after prolonged cold storage. According to a sensory assessment of boiled mackerel fillets, the shelf life of thawed mackerel after five months of cold storage is about 4-6 days. The total number of micro-organisms and H2S-producing micro-organisms was lower than is usually seen at the end of the shelf-life of micro-organisms. Histamine was not detected (<5 ppm) in thawed mackerel during the 9-day ice-storage period.

The Quality Index Method (QIM) is an objective, rapid and reliable sensory method. The aim of the present study was to develop a QIM scheme for frozenthawed Atlantic mackerel (Scomber scombrus) stored in ice at 0 ° C and evaluate the scheme in a shelf life study. The mackerel was evaluated with sensory evaluation (QIM and generic descriptive analysis (DA)), microbial counts (Total viable counts (TVC) and H2S-producing bacteria) were estimated and histamine measured for up to nine days. The main result of this study vas the QIM scheme to evaluate freshness of frozen-thawed Atlantic mackerel storage in ice which was developed and tested in a shelf life study. The quality index - QI (sum of scores) increased linearly with storage time on ice. The QIM for thawed mackerel is based on the evaluation of quality parameters dealing with the appearance on back and belly side, texture, color and shape of eyes, mucus, color and odor of gills and appearance of gill filaments and dissolution of viscera. The maximum sum of scores (QI) can be 19. A method to evaluate cooked mackerel was also developed (general descriptive analysis-DA). Newly thawed mackerel had fresh oil, metallic and sweet odors and flavors. The main limitation of shelf life in chilled storage after thawing were sensory characteristics describing spoilage such as rancid odor and flavor which can be prominent in fatty fish species after extended frozen storage. According to sensory evaluation of cooked mackerel, the shelf life of thawed mackerel after five months of frozen storage is around 4-6 days. Counts of TVC and H2S producing bacteria were relatively low at the end of shelf life. Histamine was not detected (<5 ppm) in the thawed mackerel during the storage time of nine days on ice.

Þóra Valsdóttir

Traditional skyr. Comparison of home-made and factory-made skyr - Pre-survey / Traditional skyr. Comparison between homemade and industrial produced skyr - Preliminary study

Kolbrún Sveinsdóttir

Development of Quality Index Method and shelf life of thawed mackerel (Scomber scombrus) / Development of Quality Index Method and storage life of thawed mackerel (Scomber scombrus)

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