Agriculture 4. Technologies of storage and processing of agricultural products

Doc. Tech. Sc. V. Yu. Ovsyannikov, Doc. Tech. Sc. N.N. Lobatchyova, postgraduate student Ya.I. Kondrateva, undergraduate student N.I. Bostynets

Voronezh State University of Engineering Technologies, Russia

Investigation of fruit juice concentration in

the freeze  machines

The influence of the initial solids content in the starting apple juice, temperature and rotational speed of the drum on the final solids content of the concentrated product was investigated. [1].

According to the experimental data received we derived dependences of dry solids content in a concentrated product on the drum wall temperature, the frequency of its rotation and the initial solids content in the starting material (Fig. 1-3).

Fig. 1. Dependence of solids content DSf in the frozen apple juice on the drum wall temperature t and  the initial solids content DSi at drum speed n = 0,08 s^-1.

The analysis of the curves obtained indicated that an increase in the average temperature of the drum wall results in the monotonous increase of the moisture content in the concentrated product. Increase of the initial solids content in the tested juice causes a decrease in the thickness of the ice layer frozen on the freezing drum surface [2].

The analysis of the graphs characterizing dry solids content in the concentrated apple juice depending on the drum rotation speed showed that this dependence is nonlinear, and dry solids content increases with the decreasing of the drum rotation speed. Similar curves drawn for apple juice with increased initial solids content show a significant decrease in the content of dry solids in the concentrated product.

Fig. 2. Dependence of the final solids content DSf in the frozen apple juice on the drum wall temperature t and the frequency of its rotation n with the initial solids content DSi equal to 11.0 %.

According to the studies, it was concluded that the greatest impact on the value of the final dry solids content has the wall temperature of the drum and its rotational speed. Increase in the drum rotation speed reduces the dry solids content in the concentrated product as well as increases the product loss carried away by the rotating drum.

Obtaining of the concentrated apple juice is possible at an average temperature of the drum wall equal to  -22 - 20 °C as well as in the compliance to other rational parameters   of freezing [2]. At the same time the dry solids content in the solution obtained by melting the ice frozen, lies within a comparable proportion of dry solids drained with the ice in foreign industrial freezing units.

Fig. 3. Dependence of the final solids content DSf in the frozen apple juice on the drum rotational speed n and the initial solids content DSi with

the drum wall t = -20 °C.

The results of the investigations can be useful in calculating the heat transfer process during the concentration in  drum freezing machines, in the development of technology and  equipment design of  the concentrated juices production.

Bibliography list:

1. Sergey T. Antipov Heat and mass transfer while concentrating liquid media by freeze drying [Text]/ S.T. Antipov, V.Е. Dobromirov, V.Yu. Ovsyannikov; Voronezh state technology academy. Voronezh, 2004. – 208 p.

2. Vitaly Yu.Ovsyannikov Determination of the modes of apple juice freeze drying with the concentration process [Text]/ Agricultural products storage and processing. № 7. 2012. - P. 16-18.