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Chapter 2
Formulation and processing of selected frozen food prototypes

General unit operations commonly applied to all fruits and vegetables are given in the previous section, however specific preparations are required for each kind. Therefore, food prototypes based on fruits and vegetables are used to demonstrate the freezing application on specific food products.

2.1 Selecting a formulation for mixed fruits

One of the most common commercially frozen fruit products is mixed frozen berries as is shown in Figure 16. The mixtures typically contain combinations of raspberries, blackberries, blueberries, and strawberries. There is a wide range of mixtures available in the market for frozen berry combinations. Raspberries and blackberries for example, which are known to freeze well and retain their wholeness and shape, dependent on the structure of the fruit, are strongly associated with their cultivar. The processing requirements for different varieties of berries do not change significantly. Therefore, a mixture of raspberries and blackberries is chosen in this case as a fruit formulation to simplify the freezing process.

Figure 16. Raspberries and blackberries.

Procedure for processing mixed berries

2.2 Selecting a formulation for mixed vegetables

Frozen mixed vegetables constitute a large portion of the frozen vegetable market and are now available in an ever-increasing variety of mixtures as is shown in Figure 17. The mixtures include three or more types of vegetables, properly prepared and blanched. The USDA standards for frozen mixed vegetables describe this item as a mixture containing three or more of the basic vegetables - beans, carrots, corn, and peas. When three vegetables are used, none of the vegetables should be more than 40 percent of the total weight; the individual percent decreases with increased number of vegetable types (Hui et al., 2001).

Figure 17. Mixed vegetables

In a mixed frozen vegetable product, vegetables of different sizes are present in the mixture. Therefore, during pre-freeze treatments, especially blanching, care must be taken to be sure all vegetables are blanched properly.

Procedure for processing mixed vegetables

Figure 18. Flow diagram of freezing process for fruit-based product.

Figure 19. Flow diagram of freezing process of vegetable-based product.

2.3 Recommendations for the processing site

Initial selection of the processing site should be based on significant considerations. The design of the general processing plant has great importance in assuring quality of the final product and the effectiveness of the process (Mayes and Telling, 1993). Some recommendations related to the location, and the general plant layout, are summarized in the following section (Herron, 1968). Also Figures 18 and 19 show a general flow diagram recommendable for freezing of fruits and vegetables respectively.

2.3.1 Location

2.3.2 General plant layout

Employees shall not be permitted to eat in food processing or packaging areas. Well located, properly ventilated dressing rooms and toilet rooms of ample size with self-closing doors shall be provided for employees (Herron, 1968).

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