Effects And Optimization Of Superheated Steam Treatment On Quality Characteristics Of Grey Oyster Mushroom (Pleurotus sajor-caju)

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Date
2017-08
Authors
Mohd Rashidi, Arini Nuran
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Universiti Sains Malaysia
Abstract
Grey oyster mushroom (Pleurotus sajor - caju) is one of the edible mushrooms which are cultivated commercially in Malaysia. Mushroom’s palatability can be improved by heat treatment, however the nutritional component will be affected. This study was aimed to determine the physicochemical, microbial quality and functional properties of fresh Pleurotus sajor - caju together with the optimization of superheated steam (SHS) treatment on Pleurotus sajor - caju based on the radical scavenging activity (RSA) and the total dietary fibre (TDF). Analysis on proximate, colour, dietary fibre, microbial quality and antioxidant activity were carried out throughout this study. All the essential amino acids were found in the mushroom and the highest were valine and threonine. Pleurotus sajor - caju treated with SHS from 160 to 200 °C for 10 to 30 min were shown to have increasing the amount of ash (0.99 - 1.34 %) and carbohydrate (12.36 - 53.70 %) but significant (p < 0.05) reduction in the percentage of TDF and fat. Protein has increased after treated at each temperature for 10 to 20 min however decreased significantly after 30 min of treatment. SHS treatment can increase the total phenolic content (TPhC) as well as the antioxidant activity as treatment temperature and time increased. Optimization of SHS treatment by using Response Surface Methodology (RSM) relating to scavenging activity on DPPH and total dietary fibre was achieved at 180 ºC for 30 min yielding DPPH RSA of 80.39 ± 0.12 % and TDF of 19.80 ± 0.08 %. Water absorption capacity of optimum treated Pleurotus sajor - caju was 116.61 %. Oil absorption capacity was 87.88 %, foaming capacity was 33.33 % and foaming stability was 44.44 %. By virtue of having high fibre with low fat and high antioxidant activity, Pleurotus sajor - caju can be considered as a functional food, which can provide health benefits. In conclusion, SHS treatment can increase the antioxidant activities of Pleurotus sajor - caju and reduce the percentage of fat. The application of the SHS treated Pleurotus sajor - caju in other food products could be evaluated for future research.
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Keywords
Grey oyster mushroom , are cultivated commercially in Malaysia
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