The main objective is to effectively denature the autolysis enzymes of C. frondosa on the premise of avoiding the quality deterioration caused by overheating. The effects of the different thermal treatments (blanching at 40–80 °C for 45 min, boiling and steaming at 100 °C for 15–120 min) on the cooking yield, moisture content, protein degradation, texture, and enzyme inactivation were studied, and the inner relationship was investigated by multivariate analysis. The autolysis enzymes of C. frondosa were thermally stable and cannot be denatured completely by blanching. Boiling and steaming could efficiently inactivate the enzymes but overheating for 60–120 min reduced the cooking yield and texture quality. Boiling at 100 °C for 45 min was suitable for pre-treatment, with cooking yield of 70.3% and protein content of 78.5%. Steaming at 100 °C for at least 30 min was preferable for long-term storage and instant food, in which the relative activity was only 3.2% with better palatability.
Technological meat quality and sensory attributes of fresh and frozen lamb meat were compared. Samples were collected from two abattoirs (one small-scale, one large-scale) that use different slaughter methods in terms of chilling regime and electrical stimulation. The fresh and frozen meat samples included products from both slaughter systems. Ten twin pairs of ram lambs were used in the study, with one of each twin slaughtered at each abattoir. Fresh meat was analysed after chilling and frozen meat was stored frozen for three months and analysed after thawing. The Musculus longissimus thoracis et lumborum was analysed for colour, cooking loss, sensory attributes, Warner-Bratzler shear force (WBSF) and distribution of water and lipid within each meat sample. Meat samples analysed after frozen storage were darker, less red and more yellow than the fresh meat. Freezing and frozen storage increased fluid loss and WBSF compared with the fresh meat, due to protein denaturation. Frozen storage affected sensory attributes by increasing fatty odour, frying flavour, sour flavour, fatty flavour and liver flavour, and by reducing juicy texture and mushy texture.
Improved quality of herring for human consumption
Síld er ein af mikilvægustu fisktegundum í Norður Atlandshafi og í Eystrasalti. Þrátt fyrir að stór hluti af aflanum fari til manneldis, þá fara um 85% af síld í vinnslu á lýsi og mjöli. Almennur vilji er fyrir því að auka neyslu síldar til manneldis. Þess var mikilvægt að rannsaka mismunandi þætti sem hafa áhrif á gæði síldar og sérstaklega hvernig þeim er stjórnað af líffræðilegum aðstæðum. Aðlástæðan fyrir gæðavandamálum í síld er hátt innihald efnasambanda sem stuðla að þránun, og hafa áhrif á lit- og áferðarbreytingar, ásamt tapi næringarefna. Betri gæði leiða af sér aukna samkeppni á framleiðslu síldar á Norðurlöndum, ásamt jákvæðu viðhorfi neytenda gagnvart síldarafurðum. Meginmarkmið verkefnisins var að bæta gæði og magn síldar , til neyslu, með því að rannsaka gæði hráefnisins eftir veiðar. Lögð var áhersla á gæði strax eftir veiðar og gæði hráefnisins eftir mislangan tíma í frosti. Þættir eins og veiðistaður og veiðitími höfðu ekki áhrif á gæði síldar. Hins vegar hafði geymsla í frosti við -20°C teljandi áhrif á gæði hráefnisins.
Herring is one of the most important fish species in the North Atlantic and Baltic Sea, with an annual catch exceeding 2 million tonnes. Although a large part of these fish is used for human consumption, as much as 85% of the herring is used for industrial production of fish meal and fish oil. There is a general wish to increase the utilization of herring for human consumption. Thus, it was important to study the various parameters which influence the quality of herring, and in particular how these paramenters are controlled by biological factors. A major reason behind quality problems arising during post-harvest handling of herring is its high content of compounds that efficiently catalyzes the development of rancidity, pigmentation, texture changes and loss of nutritional value. Improved quality will result in increased competitiveness of the Nordic fish processing industry and would improve the attitude among the consumers towards herring products. The general objective of the project was to improve the quality and quantity of herring to be used for food production by investigating how natural variation in raw material characteristics affects post-harvest quality. Attention was given to the quality immediately after landing and the quality after period of frozen storage. The results indicated no clear differences in the quality of herring regarding catching place or season. The frozen storage for a prolonged time had the major influence on the quality of herring fillets.
Effect of high pressure processing in reducing Listeria spp. and on the textural and microstructural properties of cold smoked salmon (CSS)
Meginmarkmið verkefnisins var að rannsaka áhrif háþrýstings (400-900 MPa) á dauða bakteríunnar Listeria monocytogenes og gæðaþætti (myndbyggingu, áferð og lit) í kaldreyktum laxi eftir meðhöndlun í 10, 20, 30 og 60 sekúndur. Áhrif á heildarfjölda loftháðra baktería, mjólkursýrugerla og Bacillus gróa voru einnig rannsökuð. Tvær tilraunir voru framkvæmdar, önnur í Júlí 2005 og hin í Nóvember 2006. Rannsóknin sýndi að meðhöndlun með háþrýsting í stuttan tíma væri árangursrík til að bæta gæði og öryggi kaldreyktra afurða. Vegna breytinga í útliti og áferð afurðanna er þörf á frekari rannsóknum. Þessi nýja aðferð lofar góðu til að mæta kröfum um lengra geymsluþol á reyktum laxi. Rannsóknin hefur mikið gildi fyrir iðnaðinn, vegna þeirrar nýjungar að nota háþrýsting í stuttan tíma (sekúndur) til að eyða bakteríunni Listeríu í reyktum laxi og auka þannig geymsluþol þessarar verðmætu afurðar.
The main object of this research was to study the effects of high pressure processing (400-900 MPa) on the survival of Listeria monocytogenes and the characteristics (microstructure, texture and colour) of cold smoked salmon when it was processed for 10, 20, 30 and 60 seconds. The changes in counts of total aerobic bacteria, lactic acid bacteria and Bacillus spores were also studied. Two experiments were carried out, one in July 2005 and the second in November 2006. It is concluded here that the combination of high pressure and short time treatment is very effective to improve the quality and safety of cold smoked products. However, because of the changes in the visual appearance and texture, further studies are necessary. This new development is promising to meet requirements for prolonged shelf life of ready-to-eat cold smoked salmon with high microbiological quality and safety. This study is of high industrial relevance because it combines the innovative approach of using high pressure processing for short time (seconds) to reduce the number of Listeria in cold smoked salmon and thereby extend the shelf life of this valuable product.