Studies on the accelerated ripening of cheddar cheese

Ridha, Sahib Hameed (1984) Studies on the accelerated ripening of cheddar cheese. PhD thesis, University of Glasgow.

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Printed Thesis Information: https://eleanor.lib.gla.ac.uk/record=b1632855

Abstract

The aim of this work was to evaluate the use of enzymes to accelerate the ripening of Cheddar cheese. Addition of preparations of β-D-Galactosidase to the cheese Milk. The ripening of Cheddar cheese produced from lactose-hydrolysed milk (e.g. up to 60% hydrolysis of the lactose) , was only slightly accelerated even though one of the β-D-galactosidase enzymes used contained some proteolytic enzyme(s). The numbers of starter bacteria at the end of the cheesemaking process were higher in cheese made from enzyme-treated milk than from untreated control milk. The level of soluble nitrogen gradually increases in Cheddar cheese as it becomes older. In these studies higher values for soluble nitrogen were observed in cheese made from lactose-hydrolysed milk compared with control cheese made from untreated milk after similar periods of ripening. This was true for both commercial lactase enzyme preparations - one of which was highly purified while the other contained substantial amounts of protease. Cheddar cheese manufactured from the latter enzyme contained the highest level of soluble nitrogen throughout the ripening period and this could be associated with appreciable acceleration of the ripening of the cheese. More extensive hydrolysis of the casein fractions was also evident in 6-month old Cheddar cheese made from milk treated with the lactase containing protease compared with the control and also the cheese made from milk treated with highly purified lactase. Other desirable effects were achieved as the result of lactose hydrolysis of the cheese milk: (i) Reduction in the cheesemaking time. (ii) Greater judge preference for cheese manufactured from lactose-hydrolysed milk. This effect could be due to the slight increase in protein degradation of this cheese. (iii) The increased level of glucose and galactose in the whey could be a desirable feature for further processing, i.e. in the production of a sweet syrup. Addition of a commercial brand of neutral proteinase to the cheese cord Cheddar cheese was manufactured by using direct-to-vat inoculation of concentrated frozen mixed strains of mesophilic starter culture. In preliminary experiments the enzyme was provided by the manufacturer as a powdered chemical and added to the milled curd at a rate of 0.001, 0.002, 0.005 and 0.01% (w/w). Separate lots of cheese were ripened at 10° and 13°C, and the enzyme activity in the cheese as assessed by monitoring the level of soluble nitrogen, hydrolysis of casein and organoleptically. The extent of acceleration of Cheddar cheese ripening depended on the level of enzyme added to the curd; for example, experimental cheese to which 0.001 and 0.01% enzyme had been added, had characteristics at 2 months similar to those of the control cheese at 4 and 8 months respectively. In enzyme-treated cheese there was a greater liberation of the more soluble nitrogenous compounds, and gel electrophoresis showed a high reduction in β- and αs1 -caseins compared with the control. All the enzyme-treated cheese had defects in "body and texture" characteristics, and had mottled, weak body and bitter flavour. The extent of the defect was associated with the enzyme level. The changes brought about by the addition of the enzyme did not increase to any large extent after four to six months ripening. The effect of the higher ripening temperature was enhanced enzyme activity. Follow up near-commercial scale trials the neutral proteinase was supplied by the manufacturer in the form of a coating on salt to enhance homogeneity of mixing with the curd. The addition of Neutrase, 0.002, 0.003 and 0.005% (w/w) to the cheese curd increased the proteolytic activity, i.e. greater liberation of more soluble nitrogen and more extensive casein hydrolysis compared with the control made from untreated curd. The flavour intensity of cheese made from enzyme-treated curd was greater than from untreated curd but the following quality problems were observed: - bitter and unacceptable flavour(s); - open and crumbly texture; - brittle and softer body cheese; - discoloured or mottled. The extent of these defects was related to the amount of enzyme added. In order to overcome these defects in the experimental cheese, the enzymatic activity had to be stopped when the desirable flavour intensity in the cheese had been achieved. Preliminary experiments have indicated that the use of Neutrase- treated curd which results in more rapid ripening and development of cheese flavour may have advantages in the production of processed cheese.

Item Type: Thesis (PhD)
Colleges/Schools: College of Medical Veterinary and Life Sciences
Supervisor's Name: Crawford, Dr. R. J. M.
Date of Award: 1984
Depositing User: Mrs Monika Milewska-Fiertek
Unique ID: glathesis:1984-38944
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 27 Nov 2018 14:39
Last Modified: 27 Nov 2018 14:39
URI: http://theses.gla.ac.uk/id/eprint/38944
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