Food Preservation Techniques

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Questions and Answers

What is the main principle behind food preservation through drying?

Drying reduces the water activity in food systems, which inhibits the growth of microorganisms and slows down spoilage processes, thus extending shelf life.

Describe the process of drying food using a spray dryer.

In spray drying, liquid food is atomized into tiny droplets and exposed to hot air in a drying chamber. This rapid evaporation of moisture creates a dried powder, which is separated from the air by a cyclone.

What is the main difference between oven drying and freeze drying in terms of the phase change involved?

Oven drying involves water changing from liquid to gas, while freeze drying involves water directly changing from solid (ice) to gas (water vapor) through sublimation.

What are two advantages of freeze drying compared to oven drying?

Freeze drying preserves the original flavor and texture of the food better than oven drying, and it also leads to less nutrient loss. Signup and view all the answers

Why is using freeze drying beneficial for preserving the aroma of food products compared to oven drying?

Freeze drying uses low temperatures, which helps to minimize the loss of volatile aroma compounds that would evaporate at higher temperatures used in oven drying. Signup and view all the answers

Explain the significance of the sublimation process in freeze drying.

Sublimation is the key process in freeze drying where ice directly changes to water vapor, removing moisture without damaging the food structure by high temperatures like in oven drying. Signup and view all the answers

What is the role of the atomizer in a spray drier?

The atomizer converts the liquid food into a fine mist of droplets, maximizing the surface area for rapid evaporation. Signup and view all the answers

How do drying parameters like pump speed, inlet temperature, air flow rate and compressor pressure affect the drying process?

These parameters influence the evaporation rate, droplet size, and drying time, ultimately affecting the properties of the final dried product. Signup and view all the answers

Based on the provided information, describe two advantages of freeze drying over oven drying.

Advantages of freeze drying over oven drying include preservation of food quality by avoiding high temperatures and minimizing the loss of volatile compounds like aroma. Signup and view all the answers

What is the purpose of dividing the banana slices into two groups and drying them at different temperatures in the oven drying experiment?

To observe and compare the effects of different drying temperatures on the color, hardness, appearance, and aroma of the dried banana slices. Signup and view all the answers

Explain the function of the cyclone in a spray dryer.

The cyclone uses centrifugal force to separate the dried food particles from the hot air stream, collecting the powder in a collection bottle. Signup and view all the answers

Why is spray drying commonly used for producing high-value products in powder form?

Spray drying can produce high-quality, consistent powder products that are well-suited for long-term storage and distribution, making it suitable for high-value applications. Signup and view all the answers

Explain the role of heat in the drying process, as described in the experiment.

Heat is essential for providing energy to evaporate water from the banana slices, thus removing moisture and leading to drying. Signup and view all the answers

How does drying help to preserve food? Briefly explain the mechanism.

Drying reduces water content in food, hindering the growth of microorganisms and slowing down enzymatic activity, which are responsible for spoilage. Signup and view all the answers

What is the expected outcome of drying banana slices at a lower temperature compared to a higher temperature in terms of color, hardness, and aroma?

Drying at a lower temperature would likely result in a lighter color, softer texture, and a more intense aroma compared to drying at a higher temperature. Signup and view all the answers

What is the main function of the atomizer in a spray dryer?

The atomizer sprays the liquid feed into fine droplets to increase the surface area for drying. Signup and view all the answers

Why is a peristaltic pump used in the spray drying process?

A peristaltic pump is used to transport the liquid feed consistently to the atomizer. Signup and view all the answers

How does the cooling effect of freezing improve the quality of preserved foods?

Freezing slows down enzyme activity and microbial growth, preserving the food's texture, flavor, and nutritional value. Signup and view all the answers

What causes the difference in moisture content of milk powder from the cyclone and collection bottle?

The cyclone captures larger droplets, leading to lower moisture content, while the collection bottle holds finer droplets with higher moisture content. Signup and view all the answers

Explain the purpose of blanching before freezing food.

Blanching deactivates enzymes that can cause flavor and color degradation during storage. Signup and view all the answers

What is freezer burn and how does it affect frozen foods?

Freezer burn is the drying of a food's surface due to moisture loss, leading to texture and flavor changes. Signup and view all the answers

How can the packaging of frozen food impact its quality?

Proper packaging minimizes air exposure and moisture loss, reducing the risk of freezer burn. Signup and view all the answers

Calculate the production percentage of milk powder if 800g was obtained from a 1000g feed.

The production percentage is 80%. Signup and view all the answers

What are the two physical characteristics analyzed in the snap beans after thawing?

Appearance and odor. Signup and view all the answers

Explain the role of blanching in the freezing process of snap beans.

Blanching halts enzyme activity that can cause loss of flavor, color, and texture during freezing. Signup and view all the answers

What immediate action is taken after cutting the snap beans into 2 cm pieces?

The cut snap beans are divided into two portions. Signup and view all the answers

What is the storage temperature required for the snap beans in the freezer?

-18°C. Signup and view all the answers

What is the main difference in treatment between the two groups of snap beans in Part II?

One group is packed into a plastic bag while the other is left unpackaged on a tray. Signup and view all the answers

How long are the snap beans stored in the freezer before being analyzed?

1 week. Signup and view all the answers

What happens to the snap beans after they are removed from the freezer?

They are allowed to thaw at room temperature. Signup and view all the answers

Why is packaging crucial in the freezing of foods?

Packaging prevents freezer burn and preserves the quality of the food during storage. Signup and view all the answers

What is the main difference between high acid and low acid foods in terms of pH?

High acid foods have a pH of less than 4.6, while low acid foods have a pH of more than 4.6. Signup and view all the answers

What temperature range is generally adequate for canning low-risk foods?

The temperature range for canning low-risk foods is between 85°C to 100°C. Signup and view all the answers

What specific adjustment is made to the sucrose solution before using it in canning?

The sucrose solution is adjusted to a pH of 3.5 using citric acid. Signup and view all the answers

Why are foods with a water activity higher than 0.85 and a pH greater than 4.6 categorized as high-risk?

They are categorized as high-risk because pathogenic microorganisms can grow and multiply in them. Signup and view all the answers

What process is performed on the papaya slices before placing them in sterilized cans?

The papaya slices are blanched by immersing them in boiling water for 2 minutes. Signup and view all the answers

What substance is added to the sucrose solution before canning it with papaya?

A 5% calcium chloride solution is added to the sucrose solution with calcium. Signup and view all the answers

What is the first step in the preparation of papaya for canning?

The first step is to remove the outer skin and core of the fruits. Signup and view all the answers

What must be done with the water after blanching the papaya slices?

The excessive water must be drained after blanching. Signup and view all the answers

How does BHA function to prevent rancidity in fried banana slices?

BHA acts as an antioxidant, inhibiting the oxidation of fats which leads to rancidity. Signup and view all the answers

What visual differences were observed between banana slices fried without BHA and those with BHA?

The banana slices fried with BHA typically retained a brighter color compared to those fried without BHA. Signup and view all the answers

Explain the role of the oil temperature in frying banana slices with and without BHA.

The oil temperature at 170°C is crucial for achieving the right texture and proper cooking of the banana slices regardless of BHA addition. Signup and view all the answers

What are the four types of browning reactions mentioned, and which one is enzymatic?

The four types are caramelization, Maillard reaction, oxidation of ascorbic acid, and enzymatic browning; the only enzymatic reaction is the enzymatic browning. Signup and view all the answers

Discuss how the storage method of the fried banana slices might influence their shelf-life.

Storing fried banana slices at room temperature can expose them to air, leading to oxidation and potential rancidity. Signup and view all the answers

What consequences does non-enzymatic browning have on food quality?

Non-enzymatic browning can lead to undesirable colors and flavors, affecting the overall appeal and taste of the food. Signup and view all the answers

What is the primary enzymatic agent responsible for browning in fruits like bananas?

The primary enzymatic agent responsible for browning is polyphenol oxidase (PPO). Signup and view all the answers

How might the results of frying banana slices with BHA affect consumer preferences?

Fried banana slices with BHA may be preferred due to their better appearance, aroma, and extended shelf-life. Signup and view all the answers

Study Notes

Fruit Jam Production

Fruit jams are a popular food item made from pineapple, strawberries, papaya, and other fruits.
Fruit jams are consumed with bread during breakfast, lunch, and snacks.
Jam production is a preservation method for fruits. Other methods include pickling and canning.
Jams are categorized as intermediate moisture foods (IMFs) containing 15-30% moisture.
Stability of IMFs is high without refrigeration.
Preservation of IMFs is achieved through a reduction in water activity (aw).
Gel formation in jams is enabled by pectin, a naturally occurring substance in fruit.
Sugar and acid content in fruit also impact gel formation.

Jam Preparation Methodology

Pineapple is used as the fruit for jam preparation.
Outer skin and core are removed from the pineapple.
The washed pineapple is chopped into 1 cm pieces.
Pineapple pulp is created using a blender, aided by distilled water.
Pineapple pulp is divided into 4 portions for various treatments.
Table 1.1 details the different treatments and their ingredient quantities (pineapple pulp, water, sugar, pectin, citric acid).
Fruit pulp is boiled in the pot until the fruit tissues soften.
Pectin and sugar, in quantities as shown in Table 1.1, are added to the boiling fruit pulp mix while stirring.
The mixture is heated until it reaches a total soluble solid content of 60° Brix.
Citric acid, per Table 1.1, is added to the mixture, mixed well, and the pH is checked.
The mixture is poured into cans, sealed, and stored at room temperature.
Color, texture, and aroma are analyzed after one week.

Oven Drying Methodology

Bananas are peeled and sliced into 3 mm thick pieces.
A total of 16 slices are prepared and split into two groups of 8.
Banana slices are placed on separate trays.
The first group is placed in an oven and dried overnight at 60°C.
The second group is dried overnight at 100°C in a separate oven.
In the morning, properties (color, hardness, appearance, and aroma) of the dried slices are assessed.

Freeze Drying Methodology

Three groups (A, B, and C) of potatoes are prepared for the study.
Two groups (A and B) are frozen and freeze-dried while group C is oven-dried for comparison.
The freeze-dried samples (group A) have been pre-prepared.
Samples of Group B and C are to be prepped.
Potatoes are cut into 0.5cm x 2cm x 3 cm pieces.
Potatoes are placed on trays into the drying chamber.
Group A and B are freeze-dried for 24 hours.
Group C is oven-dried at 60°C for 24 hours.
Group A, B, and C samples are assessed for moisture content, appearance and color after drying.

Spray Drying Methodology

Milk is the substance used in the spray drying process.
The spray dryer's components are described and shown.
Spray drying parameters can be controlled using different components.
Procedures on how to operate a spray dryer are provided.
Milk powder is a product obtained through the spray drying of milk.
The milk powder is collected in a collection bottle and a cyclone.
The production percentage of milk powder is calculated based on the weight of milk powder collected from the bottle and cyclone divided by the weight of the initial liquid milk.
The moisture content of the milk powder is determined from both the cyclone and the collection bottle.

High Acid Food Canning Methodology

Papaya is selected as the food item.
The outer skin and core of the fruit are removed.
Papaya is cut into 1 cm slices.
Two groups of 350g papaya slices each are prepared.
Two sterilized containers are used.
Papaya slices are blanched in hot water for 2 minutes.
Syrup solutions (30% sucrose, pH 3.5, and 5% calcium chloride) are poured into each sterilized container.
The containers are exhausted in boiling water (85°C) for 10 minutes and then heated in a retort at 100°C for 15 minutes.
The containers are allowed to cool under running water.
The contents' color, firmness, and aroma are evaluated for quality after opening.

Anti-oxidants for Food Preservation

To observe the effect of using antioxidants on the occurrence of rancidity, sliced bananas are used.
The bananas are divided into 2 groups.
One group is fried without BHA, and the other is fried with BHA.
The fried bananas from both groups are stored at room temperature.
The fried bananas are assessed after three weeks for attributes (color, rancidity, and aroma).
The effect of BHA on the product's shelf life is considered.

Anti-Browning

Apples are prepared by peeling and slicing them into small pieces.
Two groups are created (1 and 2).
The first group is blanched in boiling water for 3 minutes.
The second group is not blanched.
Apples from both groups are put in a blender and blended.
Color and aroma are assessed for both groups after 30 minutes at room temperature.

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Description

This quiz explores various food preservation methods, focusing on drying techniques including spray drying and freeze drying. It covers the principles, processes, advantages, and key elements involved in these drying methods, helping students understand the significance of these techniques in food technology.