Scientific journal NRU ITMO
Series "Processes and Food Production Equipment"
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March 2019 (published: 29.03.2019)

Number 1(39)

Home > Issue > Restoration of the yolk rheological properties after freezing

UDC 664.8.037.53

Restoration of the yolk rheological properties after freezing

Bobko A.S. , Bobko A.L, Sergienko O.I., Ishevskii A.L.

The effect of the A2 phospholipase enzyme on the quality of egg yolk at different storage temperatures (–6; –12, and –18°C) was analyzed to determine the optimal storage parameters with minimal violation of its rheological properties. The object of the study was the yolk prepared from standard five-day eggs of the first category, produced at the poultry farm in Leningrad region and intended for the production of mayonnaise. A2 phospholipase was chosen as an enzyme used to stabilize the yolk and produce a product with high emulsion properties.   The yolk was subjected to freezing through shock freezing at the temperature of –35°C and air velocity of 15 m/s. Then it was stored in cooling chambers at the temperatures of –6 and –12°C for 10 months, and at –18°C for 12 months. After defrosting the viscosity ofthe yolk was determined on Engler viscometer, pH – with the help of a laboratory pH meter, thermal stability – according to the internal production procedure, organoleptic indicators – for compliance with the requirements specified in GOST 30363-2013 "Egg liquid and dry food Products. Technical conditions".  Safety indicators were determined by a third-party accredited laboratory. Tests were carried out for compliance with TR TS 021/2011 "Customs Union Technical Regulations for the safety of food products".The optimum storage temperature of egg yolk after freezing, –18°C, at which the viscosity change is less pronounced, changes in the colour of the product are less intense, and the growth of QMAFAnM is not detected. The positive effect of the A2 phospholipase enzyme on the restoration of the yolk rheological properties after defrosting, as well as on the change in pH during storage, compared with the yolk without the addition of the enzyme is evaluated. An improved technological scheme of egg yolk production is proposed, in which the addition of the enzyme occurs before its freezing, and not after its defrosting, which has a positive effect not only on the above parameters, but also on the stabilization and its emulsion properties at no additional cost.  The results of the study were implemented in the production of liquid egg products in Leningrad region. Due to cost reduction and product profitability increase the volume of sales increased by 22% within one year.
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Keywords: cold preservation; technological parameters of freezing; processing of egg yolk by enzyme; egg yolk; fermented yolk; rheological properties of egg products; phospholipase A2.

DOI 10.17586/2310-1164-2019-12-1-20-26

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