4 °C - the National Sea Grant Library
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Using Edible Film to Improve Smoked Fish Quality Yao-wen Huang and B.S. Ranawat Department of Food Science and technology University of Georgia Athens, Georgia 30602-76 10 INTRODUCTION Edible film is defined as thin layers of material which can be eaten by the consumer and provide a barrier to moisture, oxygen, oil and solute movement for the food. It can improve mechanical-handling properties, impart added structural integrity to foods, and retain volatile flavor compounds. It is sometime used to carry food additives. Edible film has been used for many years. The earliest recorded use was in 12th and 13th centuries in China. later in 16th century, “Larding” was used in England. Preservation of meats and other foodstuffs by coating with gelatin films was proposed in late 19th century. In 1930’s, hot-melt paraffin waxes became commercially available for citrus fruits. In 1950’s, carnauba wax oil-in-water emulsions were developed for coating fresh fruits and vegetables. Smoked fish is a ready-to-eat product; however, this value added seafood product has a short shelf life. Rainbow trout is a high valued commodity in seafood markets in the US. In recent years, many small rainbow trout farmers have begun to produce smoke product. Due to several commercial smoked salmon products have been recently recalled for the contamination of Listeria monocytoeenes, eliminating this pathogen becomes a timely task. In order to insure a high quality and safe smoked fish, this study was designed to evaluate edible film incorporated with an antimicrobial agent to reduce psychrotrophic bacteria population as well as eliminate the contamination of L. monocytogenes on rainbow trout. Smoked Rainbow Trout MATERIALS AND METHODS Smoked rainbow trout fillets were purchased from a commercial trout farm in north Georgia. Each fillet was cut into 5X5 cm pieces.
Edible Films Five percent mixture of 3 : 1 of hydroxy propyl methyl cellulose (I-IPMC) and methyl cellulose (MC) was suspended in 30 ml 95% ethanol. Seventy ml distilled water was added while stirring. Potassium sorbate was added at 0.3% level. After 20 min mixing, the solution was allowed to rest for 30 min to remove entrapped air. Ten ml of solution was then poured on a 20X20 cm glass plate and dried at 45-47°C for 7 hrs. Inoculation and Packaging For inoculated samples, fillets were inoculated with 1 ml of l0 4 CFU/ml of mixed strain of Listeria monocytogenes (Scott A, LCDC, V-7, and Brie) (Huang et al., 1993). Each fillet section will be wrapped either with or without film before packaging. The packaging method included overwrapped and vacuum skin packaging. All samples stored at 4 and 10°C for 24 and 15 days, respectively and sampled at 3-day intervals. Microbiological Analysis Samples were massaged for 1 min with 25 ml sterile Butterfield’s phosphate buffer. Appropriate serial dilutions were plated onto the following agars by spread plate methods. Listeria Selective Medium (Oxid, Basingstoke, UK) agar was used to enumerate the L. monocytogenes population. Plate were incubated at 35°C for 48 hrs. The psychrotrophic population was determined on plate count agar (Difco, Detroit, MI) incubated at 20°C for 72 hrs. The aerobic and anaerobic population were incubated at 32°C for 48 hrs (Speck, 1984). Data Analysis Analysis of variance was performed on the data by means of PC SAS (SAS, 1987). Ducan’s multiple range test was used to determine any significant differences among F-values at different packaging treatment and microbial populations on smoked fillets with and without edible film wrapping. RESULTS Effect of Edible Films on Microbial Populations of Smoked Trout Aerobic, anaerobic and psychrotrophic populations of vacuum skin packaged smoked rainbow trout stored at 4°C were shown in Fig. 1.1, 1.2 and 1.3. Statistically significant difference (p
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Using Edible Film to Improve Smoked Fish Quality<br />
Yao-wen Huang and B.S. Ranawat<br />
Department of Food Science and technology<br />
University of Georgia<br />
A<strong>the</strong>ns, Georgia 30602-76 10<br />
INTRODUCTION<br />
Edible film is defined as thin layers of material which can be eaten by <strong>the</strong><br />
consumer and provide a barrier to moisture, oxygen, oil and solute movement for <strong>the</strong><br />
food. It can improve mechanical-handling properties, impart added structural<br />
integrity to foods, and retain volatile flavor compounds. It is sometime used to carry<br />
food additives. Edible film has been used for many years. The earliest recorded use<br />
was in 12th and 13th centuries in China. later in 16th century, “Larding” was used in<br />
England. Preservation of meats and o<strong>the</strong>r foodstuffs by coating with gelatin films was<br />
proposed in late 19th century. In 1930’s, hot-melt paraffin waxes became<br />
commercially available for citrus fruits. In 1950’s, carnauba wax oil-in-water<br />
emulsions were developed for coating fresh fruits and vegetables.<br />
Smoked fish is a ready-to-eat product; however, this value added seafood<br />
product has a short shelf life. Rainbow trout is a high valued commodity in seafood<br />
markets in <strong>the</strong> US. In recent years, many small rainbow trout farmers have begun to<br />
produce smoke product. Due to several commercial smoked salmon products have<br />
been recently recalled for <strong>the</strong> contamination of Listeria monocytoeenes, eliminating<br />
this pathogen becomes a timely task. In order to insure a high quality and safe<br />
smoked fish, this study was designed to evaluate edible film incorporated with an<br />
antimicrobial agent to reduce psychrotrophic bacteria population as well as eliminate<br />
<strong>the</strong> contamination of L. monocytogenes on rainbow trout.<br />
Smoked Rainbow Trout<br />
MATERIALS AND METHODS<br />
Smoked rainbow trout fillets were purchased from a commercial trout farm<br />
in north Georgia. Each fillet was cut into 5X5 cm pieces.
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