42
M. Maity et al.
2.4.2 Preparation of Cheese from β-Galactosidase-Treated
and Untreated Cow Milk
Lactose-free soft cheese was prepared as described by Yossef and EI Beltagey (2014)
with some modifications. Partially purified β-galactosidase was added to cow milk at
a ratio of 1:10 (v/v). Then milk was stirred gently at 25–30 °C for 20 min. After that
milk was heated at 60–70 °C for 30 min and cooled immediately to 30–40 °C. About
0.02% calcium chloride was added and kept for 15 min. Then 1% starter culture
was mixed and kept for 3 h. Whey was discarded after adding rennet and pressed by
cheese mold. Disc-shaped cheese was stored in the refrigerator. Similarly, control
cheese was prepared with untreated (without β-galactosidase) cow milk.
2.4.3 Proximate Analysis of Cheese from β-Galactosidase-Treated
and Untreated Cow Milk
Physicochemical analyses such as moisture, ash, fat, carbohydrates, and proteins
of cow milk, control cheese, and cheese from β-galactosidase-treated milk were
analyzed according to standard replication AOAC (Association of Official Agricultural Chemists 2011) methods.
2.4.4 Estimation of Antioxidant Activity of Cheese
from β-Galactosidase-Treated and Untreated Cow Milk
Estimation of antioxidant activity involved at first the preparation of water-soluble
extract of cheese from β-galactosidase-treated and untreated milk. Water-soluble
cheese extract was prepared according to Huma et al. (2018) with slight modification. Prepared cheese was mixed with distilled water at a ratio of 1:2 and homogenized
(1000 rpm/min) for 20 min. pH of this homogenized mixture was adjusted at 4.6 by
1 M HCl. Slurry was heated in water bath (40 °C) for 1 h, followed by centrifugation (5000 rpm, 15 min) at 4 °C. Then the supernatant was filtered and taken as
a water-soluble extract for antioxidant determination. Antioxidant activities such
as 2,2
-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activity, 2,2-diphenyl-1-picrylhydrazil (DPPH) radical scavenging activity,
and ferric reducing antioxidant power (FRAP) assay of aqueous extract of cheese
from β-galactosidase-treated milk and cheese from non-treated milk were estimated
according to Rahmawati and Suntornsuk (2016) and Huma et al. (2018).
2.4.5 Microbial Load Analysis of Cheese from β-Galactosidase-Treated
and Untreated Cow Milk
Microbial load analysis was carried out for both the cheeses during storage condition
(stored for 0–30 days at 4 °C). The amount of total viable organisms, lactic acid
M. Maity et al.
2.4.2 Preparation of Cheese from β-Galactosidase-Treated
and Untreated Cow Milk
Lactose-free soft cheese was prepared as described by Yossef and EI Beltagey (2014)
with some modifications. Partially purified β-galactosidase was added to cow milk at
a ratio of 1:10 (v/v). Then milk was stirred gently at 25–30 °C for 20 min. After that
milk was heated at 60–70 °C for 30 min and cooled immediately to 30–40 °C. About
0.02% calcium chloride was added and kept for 15 min. Then 1% starter culture
was mixed and kept for 3 h. Whey was discarded after adding rennet and pressed by
cheese mold. Disc-shaped cheese was stored in the refrigerator. Similarly, control
cheese was prepared with untreated (without β-galactosidase) cow milk.
2.4.3 Proximate Analysis of Cheese from β-Galactosidase-Treated
and Untreated Cow Milk
Physicochemical analyses such as moisture, ash, fat, carbohydrates, and proteins
of cow milk, control cheese, and cheese from β-galactosidase-treated milk were
analyzed according to standard replication AOAC (Association of Official Agricultural Chemists 2011) methods.
2.4.4 Estimation of Antioxidant Activity of Cheese
from β-Galactosidase-Treated and Untreated Cow Milk
Estimation of antioxidant activity involved at first the preparation of water-soluble
extract of cheese from β-galactosidase-treated and untreated milk. Water-soluble
cheese extract was prepared according to Huma et al. (2018) with slight modification. Prepared cheese was mixed with distilled water at a ratio of 1:2 and homogenized
(1000 rpm/min) for 20 min. pH of this homogenized mixture was adjusted at 4.6 by
1 M HCl. Slurry was heated in water bath (40 °C) for 1 h, followed by centrifugation (5000 rpm, 15 min) at 4 °C. Then the supernatant was filtered and taken as
a water-soluble extract for antioxidant determination. Antioxidant activities such
as 2,2
-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activity, 2,2-diphenyl-1-picrylhydrazil (DPPH) radical scavenging activity,
and ferric reducing antioxidant power (FRAP) assay of aqueous extract of cheese
from β-galactosidase-treated milk and cheese from non-treated milk were estimated
according to Rahmawati and Suntornsuk (2016) and Huma et al. (2018).
2.4.5 Microbial Load Analysis of Cheese from β-Galactosidase-Treated
and Untreated Cow Milk
Microbial load analysis was carried out for both the cheeses during storage condition
(stored for 0–30 days at 4 °C). The amount of total viable organisms, lactic acid