Growth dynamics of microorganisms in rainbow trout marinated with fruit and berry pomaces
Laen...
Kuupäev
2024
Kättesaadavus
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Estonian University of Life Sciences
Abstrakt
In recent years, there has been an increasing trend in food technology to increase the use of various
plant-origin materials including fruit, and berry pomaces, a by-products of juice production, in the composition
of food of animal origin. This is mainly because of potential health benefits of plant derived bioactive components
to human health. Also, this is in good agreement with the principles of the circular bioeconomy. The use of berry
pomaces reduce the food waste and provides added value to the final products. The aim of the study was to
evaluate the effect of apple, black currant, rhubarb or tomato pomace aqueous extracts containing marinades on
the growth dynamics of microorganisms in raw rainbow trout within the determined study period.
Fresh rainbow trout (Oncorhynchus mykiss) fillets were purchased from a local fish farm. The pomaces were
obtained after juicing of the apples (Malus domestica Borkh.), black currants (Ribes nigrum L.), rhubarbs (Rheum
rhaponticum L.) and tomatoes (Lycopersicon esculentum Mill.). Aqueous pomace extracts were prepared in a
ratio of 1:10 (w/v), calculated for a solids content of 10%. The pomace extracts were pasteurized at 80 ºC for 20
minutes, sealed airtight in glass bottles and cooled. Finally for each pomace extract the 3% sugar, 3% salt, 1%
acetic acid and 0.25% citric acid were added to obtain the marinade. Enumeration of aerobic mesophilic
microorganisms, yeasts and moulds, presumptive Pseudomonas spp., and L. monocytogenes was performed
according to the ISO standards. The challenge test in accordance with the technical guidance document (version
4 of 1 July 2021) of the European Union Reference Laboratory for L. monocytogenes was carried out to determine
the growth potential (δ) of L. monocytogenes in marinated fish samples.
It was found that in most of the samples the number of aerobic mesophilic microorganisms increased during the
22-day study period. However, interestingly in all samples, there was a decrease in the number of Pseudomonas
spp. from 3.42 log10 cfu/g to 1.00 log10 cfu/g. Also, the numbers of moulds and yeasts were low in all tested
samples throughout the study period remaining between 1.00 and 2.95 log10 cfu/g. The growth potential of L.
monocytogenes was lower than 0.5 log10 cfu/g in all tested samples during the 15-day challenge period, which
means that the marinated product did not support the growth of L. monocytogenes. Comparing the results of initial
and final numbers of L. monocytogenes, a tenfold decrease in the average counts of the pathogen was counted in
the black currant pomace, followed by the apple pomace and rhubarb pomace fish samples. Within the entire study
period, the lowest average numbers of L. monocytogenes were observed in the black currant pomace containing
fish samples compared to the control. On the final day of the durability study, day 15, the lowest growth potential
of L. monocytogenes was found for black currant pomace and apple pomace containing marinated fish samples.
The use of apple, black currant, rhubarb and tomato pomaces in marinades can ensure a sufficiently long and
microbiologically safe shelf-life for the marinated raw rainbow trout products.
Kirjeldus
Märksõnad
marinated rainbow trout, pomaces, microbiological quality and safety, valorization of food byproducts, Listeria monocytogenes, abstracts