Physico-chemical characteristics
The total soluble solids (TSS) content in fruit juice was
recorded with the help of hand refractometer (ATAGO,
model: HR-5[0–90%], Japan) by squeezing the juice with
cotton wool on to the cleaned sensor and reading was
reported as ºBrix. pH, of a known amount of fresh and
homogenized fruit juice in a 100 ml beaker was recorded
with a digital pH meter (Thermoorion, model 230A+, 9157
BN, Witchford, England) after standardizing the pH meter
with buffer solutions of pH 4 and 7 (Ranganna 1986).
Titratable acidity was determined as per Horwitz (1980)
method. A known weight of fruit sample was crushed and
326 J Food Sci Technol (March–April 2013) 50(2):325–331
taken in to 250 ml volumetric flask and the volume was
made up. After filtration, 10 ml of filtrate was titrated
against 0.1 N NaOH using phenolphthalein as indicator.
The reducing sugar content was estimated by Lane and
Eynon’s volumetric method (Horwitz 1980). Pectin content
was determined by Carre and Hayne’s methods as described
by Ranganna (1986) and expressed as percent calcium
pectate. Polygalacturonase activity (PG) was determined by
the method described by Mahadevan and Sridhar (1982).
The enzyme action mixture consisted of enzyme extract
(2 ml) which was prepared by crushing fruit flesh, 4 ml of
sodium polypectate substrate (by dissolving 750 mg of the
sodium polypectate in 100 ml of acetate buffer, pH 5.2,
heated to 50–60 °C and placed in a blender for mixing) and
1 ml of acetate buffer. Using Ostwald-type viscometer the
content was mixed by gently drawing air through the large
arm of the viscometer and suction was applied through the
small arm of the viscometer and initial efflux time of
mixture was determined. After 16 hours, again the efflux
time of the mixture was measured. Anthocyanin pigments
of apple fruit skin were extracted with solvent mixture of
acidic ethyl alcohol (Ranganna 1986) and the intensity of
colour was measured through 535 nm wavelength in a
spectrophotometer against blank. Spoilage of fruits due to
fungal rots was calculated by adding up the number of
fruits spoiled on successive storage interval and calculating
their percentage on the basis of number of fruits stored
initially.
Physico-chemical characteristics
The total soluble solids (TSS) content in fruit juice was
recorded with the help of hand refractometer (ATAGO,
model: HR-5[0–90%], Japan) by squeezing the juice with
cotton wool on to the cleaned sensor and reading was
reported as ºBrix. pH, of a known amount of fresh and
homogenized fruit juice in a 100 ml beaker was recorded
with a digital pH meter (Thermoorion, model 230A+, 9157
BN, Witchford, England) after standardizing the pH meter
with buffer solutions of pH 4 and 7 (Ranganna 1986).
Titratable acidity was determined as per Horwitz (1980)
method. A known weight of fruit sample was crushed and
326 J Food Sci Technol (March–April 2013) 50(2):325–331
taken in to 250 ml volumetric flask and the volume was
made up. After filtration, 10 ml of filtrate was titrated
against 0.1 N NaOH using phenolphthalein as indicator.
The reducing sugar content was estimated by Lane and
Eynon’s volumetric method (Horwitz 1980). Pectin content
was determined by Carre and Hayne’s methods as described
by Ranganna (1986) and expressed as percent calcium
pectate. Polygalacturonase activity (PG) was determined by
the method described by Mahadevan and Sridhar (1982).
The enzyme action mixture consisted of enzyme extract
(2 ml) which was prepared by crushing fruit flesh, 4 ml of
sodium polypectate substrate (by dissolving 750 mg of the
sodium polypectate in 100 ml of acetate buffer, pH 5.2,
heated to 50–60 °C and placed in a blender for mixing) and
1 ml of acetate buffer. Using Ostwald-type viscometer the
content was mixed by gently drawing air through the large
arm of the viscometer and suction was applied through the
small arm of the viscometer and initial efflux time of
mixture was determined. After 16 hours, again the efflux
time of the mixture was measured. Anthocyanin pigments
of apple fruit skin were extracted with solvent mixture of
acidic ethyl alcohol (Ranganna 1986) and the intensity of
colour was measured through 535 nm wavelength in a
spectrophotometer against blank. Spoilage of fruits due to
fungal rots was calculated by adding up the number of
fruits spoiled on successive storage interval and calculating
their percentage on the basis of number of fruits stored
initially.
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