Comparison of chemical, microbiological and histological changes in fresh, frozen and double frozen rainbow trout (Oncorhynchus mykiss)

The final quality of fish meat depends on the chemical and microbiological quality of fish at the time of freezing as well as on other factors including storage temperature and freezing rate. Analysis of chemical composition (water, protein and fat content), expressible drip, total volatile nitrogen levels, microbiological analyses (total viable counts, Enterobacteriaceae, psychrotrophic bacteria) and histological examinations on dorsal skeletal muscles were carried out to distinguish fresh, frozen and double frozen rainbow trout (Oncorhynchus mykiss). Significantly higher expressible drip and total volatile base nitrogen concentrations (P < 0.05) were observed in frozen and double frozen trout, whereas chemical composition of fresh fish muscles was not significantly affected by freezing. The highest total viable counts, counts of Enterobacteriaceae and psychrotrophic bacteria were determined in double frozen trout. The light microscopy of fresh trout muscles did not show any microstructural changes, whereas deformations of muscle fibres and optically empty areas were found in frozen trout. Remarkable defects of the muscle structure in double frozen trout were demonstrated and total disruption of muscle fibres was found. The freezing of trout resulted in various structural changes in the dorsal skeletal musculature. This is a first study comparing changes in fresh, frozen and repeatedly frozen trout. Chemical, microbiological and subsequent histological examinations can be used for revealing the foul practices confusing the consumer with offering thawed fish instead of fresh cooled fish.

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Effect of Gelatin Coated Rosemary Extract (Rosmarinus Officinalis L.) on the Quality of Refrigerated Duck Meat

Agricultural Science Digest - A Research Journal ◽

10.18805/ag.d-180 ◽

2019 ◽

Vol 39 (04) ◽

Author(s):

Kimia Banikarimi K Rai ◽

Habibollah Mirzaei K Basu ◽

Mohammad Farsi K Basu

Keyword(s):

Storage Period ◽

Edible Coating ◽

Water Holding Capacity ◽

Rosemary Extract ◽

Control Group ◽

Total Volatile ◽

Psychrotrophic Bacteria ◽

Rosmarinus Officinalis L ◽

Water Holding

The effect of edible coating of gelatin (1, 2 and 3%) containing aqueous extract of rosemary (1% and 2%) on physiochemical (pH, total volatile nitrogen, peroxide values and water holding capacity) and microbiological (psychrotrophic) properties of duck fillet were evaluated. The pH of coated samples were significantly (plessthan0.05) lower than that of untreated sample. TVN (total volatile nitrogen) value increased with storage period in all the samples but coatings significantly decreased production of TVN compared to the control. Also the coatings decreased lipid oxidation of the meat as rosemary postponed primary oxidation of fillet, while this parameter in control group was sharply increased by time. WHC (water holding capacity) increased significantly (plessthan0.05) with storage period and level coatings. Coating had a significant reducing effect on growth of psychrotrophic bacteria during 9 days at 4°C. In conclusion, gelatin edible coating enriched with rosemary could retard chemical and microbial reactions related to spoilage of meat during refrigerated storage.

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The effect of different cooking methods on proximate composition and lipid quality of rainbow trout (Oncorhynchus mykiss)

International Journal of Food Science & Technology ◽

10.1111/j.1365-2621.2006.01298.x ◽

2007 ◽

Vol 42 (7) ◽

pp. 874-879 ◽

Cited By ~ 24

Author(s):

Bahar Tokur

Keyword(s):

Rainbow Trout ◽

Oncorhynchus Mykiss ◽

Proximate Composition ◽

Cooking Methods ◽

Rainbow Trout Oncorhynchus Mykiss ◽

Lipid Quality

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Fate of Escherichia coli O157:H7 in the Presence of Indigenous Microorganisms on Commercially Packaged Baby Spinach, as Impacted by Storage Temperature and Time†

Journal of Food Protection ◽

10.4315/0362-028x-72.10.2038 ◽

2009 ◽

Vol 72 (10) ◽

pp. 2038-2045 ◽

Cited By ~ 35

Author(s):

YAGUANG LUO ◽

QIANG HE ◽

JAMES L. McEVOY ◽

WILLIAM S. CONWAY

Keyword(s):

Escherichia Coli ◽

Product Quality ◽

Elevated Temperatures ◽

Storage Temperature ◽

Escherichia Coli O157 ◽

Indigenous Microorganisms ◽

E Coli ◽

Psychrotrophic Bacteria ◽

Survival And Growth

This study investigated the effect of storage temperature and time on the survival and growth of Escherichia coli O157:H7, the growth of indigenous microorganisms, and the changes in product quality of packaged baby spinach. Commercial packages of spinach within 2 days of processing were cut open at one end, sprayed with fine mists of E. coli O157:H7 inoculum, resealed, and then stored at 1, 5, 8, and 12°C for 12 days until their labeled best-if-used-by dates. Microbial enumeration and product quality evaluation were conducted on day(s) 0, 3, 6, 9, and 12 postinoculation. Spinach held at 12°C supported significant (P < 0.001) E. coli O157:H7 growth, with a 1.0-log CFU/g increase within 3 days postinoculation, which was followed by additional growth during continued storage. E. coli O157:H7 grew slowly when held at 8°C, with a significant (P < 0.01) level of growth reached after 6 days of storage. However, on products held at 1 and 5°C, E. coli O157:H7 populations declined significantly (P < 0.01 and P < 0.001, respectively) within 3 days of storage. Aerobic mesophilic bacteria, psychrotrophic bacteria, and yeast and mold populations increased significantly at all storage temperatures, with more growth on products held at elevated temperatures. Product quality scores remained high within the first 6 days of storage, with a sharp decline noted on samples held at 12°C on day 9. Results suggest that E. coli O157:H7 can grow significantly on commercially packaged spinach held at 8°C or above before significant product quality deterioration occurs.

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