| Tez Künye | Durumu | ||
| The effects of packaging systems on quality and safety of herring / Yazar:FATİH ÖZOĞUL Danışman: PROF. TONY TAYLOR ; DR. PETER QUANTİCK Yer Bilgisi: University of Lincoln / Yurtdışı Enstitü / Biyolojik Veri Bilimi Ana Bilim Dalı Konu:Biyoloji = Biology Dizin: | Onaylandı Doktora İngilizce 2001 287 s. | ||
| Modified atmosphere packaging (MAP) and vacuum packaging (VP), along with refrigeration, havebecome increasingly popular preservation techniques, which have brought major changes in storage,distribution and marketing of raw and processed products to meet consumer demands. Therefore, theeffects of modified atmosphere and vacuum packaging on the sensory, chemical, and microbiologicalchanges in herring with emphasis on the quality and safety parameters, and their relationships wereinvestigated. Sensory analysis showed that the observed shelf life of herring was longest in MAP (10days), followed by VP (8 days) and ice (8 days), and least with no ice storage condition (less than 4days). Both the highest K-values and concentration of biogenic amines were obtained from herring keptin boxes without ice whereas the lowest values and concentration of that were found in herring stored inMAP. Bacteria grew most quickly in herring kept in a box without ice, followed by these in ice andvacuum packing. Lowest counts were with MAP where the log phase was apparently extended.Numbers of histamine-forming bacteria increased in all treatments with increasing storage time. Highestnumbers of histamine-forming bacteria were obtained from herring stored in boxes without ice. HenceMAP was shown to effectives increase the shelf life by 2 days compared with only iced storage.Rapid HPLC methods for the determination of ATP and its breakdown products and biogenic amineswere developed using gradient elution systems. Derivatization of amines was improved by dissolvingbenzoyl chloride in acetonitrile.Histamine, cadaverine, putrescine, tyramine and agmatine production by fifteen bacterial strainsobtained from the National Collection of Industrial and Marine Bacteria (NCIMB) and NationalCollection of Type Cultures (NCTC) was investigated in amino acid decarboxylase broths. The resultshowed that histamine production by Morganella morganii (10466), Klebsiella pneumoniae (673),Morganella morganii (235) and Hafnia alvei (11999) was 4038 mg/L, 3416 mg/L, 75 mg/L and 115mg/L, respectively in histidine decarboxylase broth. Thus the production of histamine can differmarkedly within the strains of the same bacterial species.Bacterial strains were isolated from fresh herring, herring spoiled after storage in a box without ice, VPand MAP. The microflora of fresh herring was dominantly Pseudomonas (30%), Enterobacteriaceae(23.2%), Vibrio (13.3%) and Moraxella (13.3%). However, the microflora of herring stored in VP andMAP was dominated by species belonging to Vibrio (23.3%) and Moraxella (20%).The formation of histamine, cadaverine and putrescine by these bacteria isolated from the herring wasalso investigated in histidine, lysine and ornithine decarboxylase broth, respectively. The highesthistidine decarboxylase activities were observed in Klebsiella oxytoca, Hafnia alvei and Proteusvulgaris which produced 396 mg and 232 mg and 54 mg histamine/L, respectively in histidine-enrichedbroth. The accumulation of cadaverine by Klebsiella oxytoca and Hafnia alvei was 325 mg/L and 208mg/L, respectively. All strains isolated produced putrescine in an ornithine-enriched broth, ranging from3 mg/L to 249 mg/L. The production of putrescine by Klebsiella oxytoca and Hafnia alvei was 249 mg/Land 195 mg/L, respectively. This showed that these species could account for the production of biogenicamines during the storage of herring. | |||