Han, Ng Sze
(2017)
Dietary fibre-rich oyster mushroom (pleurotus sajor-caju) powder as food ingredient and its application in developing low-glycaemic biscuit.
Masters thesis, Universiti Sains Malaysia.
Abstract
Consumer’s demand for functional food is increasing due to high prevalence of non
communicable diseases. Grey oyster mushroom (Pleurotus sajor-caju, PSC) which
cultivated widely in Malaysia possesses various medicinal properties but lack of
attention on its diabetes-related physiological function and its application in functional
food development. Hence, this study aimed to determine the nutritional values,
functional properties, storage stability, in vitro and in vivo hypoglycaemic effects of PSC
powder as well as its application in developing low-glycaemic index (low-GI) biscuit.
The effects of PSC powder as wheat flour replacer (0, 4, 8 and 12%) in biscuit on
nutritional, physicochemical, textural and sensorial properties as well as GI were
examined. Results showed that PSC powder contained appreciable amounts of protein
(22.41%), ash (7.79%), dietary fibre (DF) (56.99%) and β-glucan (3.32%) but negligible
amounts of sucrose (0.19%) and fat (2.30%). It also featured water holding capacity
(13.46 g/g), oil holding capacity (8.52 ml/g), swelling capacity (19.49 ml/g) and
emulsifying activity (51.67%). Storage study revealed that PSC powder exhibited
significant lower L* colorimetric value meanwhile microbial counts remained
unchanged with increasing storage temperature and duration. The mechanisms of PSC
powder to elicit the in vitro hypoglycaemic effects were through glucose adsorption,
retardation of glucose diffusion across dialysis membrane and delayed glucose release
from starch by inhibition of α-amylase activity. The hypoglycaemic potentials of PSCpowder were higher than oat, barley and atta flour. In addition, PSC aqueous extract
(PSCE) demonstrated significant blood glucose (BG) reduction and glucose tolerance
improvement in normal and streptozotocin (STZ)-induced diabetic rats. The PSCE at
750 mg/kg was identified as the optimum effective dose and its effects were comparable
to metformin (150 mg/kg). In 21-days study, BG, body weight and urine sugar in PSCEtreated
diabetic rats were reported significant improvement compared to control diabetic
rats. PSC powder incorporation in biscuit resulted in increased nutritional values
particularly DF, disturbed structure and reduced diameter of starch granules, reduced
pasting viscosity, reduced enthalpy of starch gelatinisation, increased proportion of
slowly digestible starch and eventually reduced GI of biscuit. The addition of 8% PSC
powder is the best formulation in developing low-GI (GI=49), high TDF (8.62%) and
well-accepted functional biscuit. Therefore, PSC powder can be used as a food
ingredient and in development of low-GI biscuit.
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