Nader Cheraghi; Ebrahim Alizadeh Doughikollaee; Mohsen Shahriari Moghadam
Abstract
Introduction: Recently, the high nutritional value of fish and other seafood has caused continuously increasing their consumption in human diet. The meat quality can be decreased during storage due to physical, chemical and microbial changes. Thus, the different methods of preservation should be used ...
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Introduction: Recently, the high nutritional value of fish and other seafood has caused continuously increasing their consumption in human diet. The meat quality can be decreased during storage due to physical, chemical and microbial changes. Thus, the different methods of preservation should be used to improve the quality and increase the shelf-life of the product. The application of bacteriocinins has been increased to extend the shelflife of food products. Nisin is a kind of bacteriocinins that is produced by Lactococcus lactis bacteria and used as food preservatives. It is accepted such as food additive in many food commodities. Bacteriocinins showed synergistic effects when they used with other antibacterial compounds such as natural preservatives and phenolic compounds. Literature review showed that the antibacterial compounds such as sodium acetate play an important role in preventing the growth of bacteria and increasing the shelf life of fish during different storage conditions. Conventional optimization procedures are performed by altering one parameter at a time and keeping all other parameters at fixed levels. However, these procedures are time consuming and require more experimental data sets. Recently, the use of an orthogonal array approach called ‘Taguchi method’ has been successfully examined in the different field of sciences. Therefore the aim of this research was to investigate the effects of nisin, sodium acetate and temperature on the growth of Staphylococcus aureus in Ctenopharyngodon idella fillet using Taguchi experimental design with an array L4 (23).
Materials and methods: The fresh Ctenopharyngodon idella with weight of 1 kg were purchased from market (Zabol, South east of Iran) and transported in isothermal iceboxes to the fish product processing laboratory at University of Zabol in 2016. The fishes were cleaned and filleted. Fillets after inoculated with Staphylococcus aureus (103 Log CFU/g) and added nisin (750 and 1000 IU/g) and sodium acetate (1 and 2 %) were stored in different temperatures (4 and 8 °C). Chemical parameters (pH, PV, TBA and TVB-N) and Staphylococcus aureus count were measured at 0, 3, 6 and 9 days. Microscopic analysis was used to observe the microstructure changes at end of storage. The experiments were performed in three replicates.
Results & discussion: The present study showed that the lowest and highest Staphylococcus aureus growth was observed in treatment 2 (sodium acetate 2%, nisin 750 IU/g, temperature 4°C) and control at 4 and 8° C, respectively. It is noticeable that the growth of Staphylococcus aureus decreased in treatment 3 (sodium acetate 2%, nisin 1000 IU/g, temperature 8° C) during storage at 8° C. Also, the results showed that the temperature was most important factor on the growth of Staphylococcus aureus in the beginning of experiment and the other factors showed their effect during storage. Therefore, the highest and lowest effect was related to temperature and nisin at the end of experiment, respectively. In the present study, the additives could be prevented the growth of bacteria with except in treatment 4 (sodium acetate 1%, nisin 750 IU/g, temperature 8° C). The inhibitory effects of nisin and sodium acetate on the growth of Staphylococcus aureus was better shown with increasing storage time. The TVB-N of fillets increased during storage but this increase was lower in treatment 2 than the other treatments. The temperature and nisin had a significant effect (p
Masumeh Molashahi; Ebrahim Alizadeh Doughikollaee; Ghorbanali Mahghani
Abstract
Introduction: Fish salting is a traditional method of processing in most countries including Iran. There are different methods of salting which can be used for producing different salted products. There is variation in the amount of salt used in the salting process depending on the context of use.Salting ...
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Introduction: Fish salting is a traditional method of processing in most countries including Iran. There are different methods of salting which can be used for producing different salted products. There is variation in the amount of salt used in the salting process depending on the context of use.Salting was done simultaneously with salt penetration into the muscles of fish and water dripping out of the fish tissue, which lead to prevention and/or reduction of microbial and enzyme activity. Wet salting using Pickel method is one of the methods of salting in which the dry salt is used to remain together with the water dripped out of the muscle in the vessel during salting. This method results in better preservation of fish against the biological spoilage, better taste and suitable distribution of salt in the texture. The importance of this method compared with other methods of salting is its ability in protecting the texture of fish against oxidation because of high rate of salt penetration. Using different salting methods affect weight change of fish. That is, the salted fish produced using wet salting method is heavier than the fish salted through dry method. Fish breeding especially that of silver carp is one of the important activities of aquaculture in our country. This is because of high rate of silver carp production and provision of a product with a better taste to markets. To assess the effectiveness of wet salting during refrigerated storage (4˚ C), In this study physicochemical, microbiological and sensory evaluation of salted silver carp would be employed. Materials and methods: The fresh silver carps with weight of 0.5 kg were purchased from market (Bandar Torkman, North Iran) and transported in isothermal iceboxes to the fish control quality laboratory at Ashoradeh Island in 2012. The fishes were cleaned and salted with 10 and 20% concentrations and then stored in refrigerator (+4°C). Chemical parameters (Humidity, Protein, Salt, PV and TBA), pH, Microbial parameters (TVC, PTC, and Halophile) and sensory analysis were measured at 0, 3, 6, 9 and 12 days. The experiments were performed in three replicates. Results & Discussion: The present study showed that by increasing the salt concentration from 10 to 20 % at 4 ° C the salt amount of salted fish muscle changed from 10.70 to 13.60 after 12 days of refrigerated storage. This suggests that an increase in salt concentration result in higher salt absorption. The difference between the results of two treatments in different times were statistically significant (P