Page 40 - FoodFocusThailand No.143_February 2018

SMART PRODUCTION

Thermal processing is one of the most widely
used unit operations employ in food industry to
preserve food. The method is aimed to destroy
all microorganisms and enzyme in food products,
which are cause of food borne disease, in
particularly pathogen, toxin, parasite, and insects,
which can harm consumer’s health. The use of
high temperatures with long period can destruct
microorganism and enzyme better than the use
of low temperature with short time. However,
the use of high temperature with short time can
also extend shelf life as well as the use of low
temperature with long time. The efficiency of
the method is it can preserve smell, taste, and
nutrition of the food products.

Thermal Processing of Foods

There are many types of thermal processing employed by the food microorganisms. The pasteurized products must be consumed within
industry. Each type of heat processing has a particular propose. Hence, three days to one weeks after opening. This method is used for many
the level of temperature is relied on the propose required to change food kinds of food including solid, liquid, condense, and mix texture food,
quality, as well as period of food preservation such as blanching, as well as with food before containing, and with food in sealed
pasteurize, frozen, baking, grilling, frying, and sterilize and etc. The use container. Moreover, there are many studies found that pasteurization
of heat in food processing is fundamental to the use of heat to evaporate is a way to maintain the natural nutrition of the food, as well as the
water. Processed food in hermetically sealed container is to prevent freshness of the food as the heat is not very high. It is suit for natural
contamination and maintain the quality of food. foods that do not require any additives such as milk and fruit juice
Thermal processing is one the widely use methods since in the past and etc. If the food is required to be stored at room temperature,
to present to preserve food. The types of thermal processing can be other methods for preserving food is needed such as to reduce water
divided as follows: (Table 1) activity, the use of sugar, salt, high concentration, acidification,
preservative, fumigation, and freezing.
1. Blanching Types of Pasteurization
Blanching is a very mild heat treatment primarily used in the food industry 2.1 In-container pasteurization, a clean-filling technique is used
by allowing food to touch with heat, hot steam, microwave, or other source to handle pasteurized a hermetically sealed container such as can,
of heat. The Blanching is carried out between 70-105°C using short time glass jar, flexible packaging including plastic bag, plastic cup, and
that suit to each type of foods. Blanching is often use in fruits and pasteurize in cooker, or tunnel pasteurizer. The heat will be transfer
vegetables before processing with various methods, such as freezing, from the container to inside of the packaging and food by allowing
dehydration, and canning. The main propose of the blanching method is the temperature and time reach the cold point of food so that it reach
to destroy enzyme. The heat from blanching will destroy enzyme, which the appropriate temperature and time that can destroy targeted
cause of food spoilage such as enzymatic browning reaction, rancidity microorganisms, which is the food borne diseases related on major
from the hydrolytic rancidity. The blanching of fruits and vegetables can raw materials and ensure food safety. A low-acid canned food (LACF)
add on calcium salt, which will be combine with pectin in plant cell in is any food (other than alcoholic beverages) with a finished equilibrium
order to help improve texture properties making fruits and vegetables pH greater than 4.6 and a water activity greater than 0.85. Those are
have a tight texture, solid, and crispy. such as meatball, sausage, tofu, and ham. Those kinds of food must
be kept in cold storage or is normally called chilled food.
2. Pasteurization 2.2 Batch pasteurization is the pasteurize by using batch
The pasteurization is aimed to destroy microorganism and enzyme, which pasteurizer, which transfer heat to food at desire temperature and
cause of food spoilage. It is a relatively mild heat treatment in which food time. Using this method, heat will be slowly transfer (Low Temperature
is heated to lower 100°C in a suitable period depending on each type of Long Time; LTLT). When targeted time has been reached, liquid food
food in different temperature such as 62.8°C for 30 minutes, or 77°C for can be contained.
15 minutes. In this regard, this method cannot destroy many types of 2.3 In-line pasteurization or continuous pasteurization refers to
microorganisms which are resistant to heat. Thus, the pasteurized the pasteurization with food in-line continuous by using the aseptic
products should be kept in low temperature to prevent food from other processing. The major procedure is to raise food temperature to the

40 FOOD FOCUS THAILAND FEB 2018