Unit 5 - Drying, Canning Concepts, and Packaging Standards | Post-harvest Management and Value Addition of Fruits and Vegetables

Table of Contents
Drying/ Dehydration of fruits and vegetables – Concept and methods, osmotic drying.
Canning -– Concepts and Standards, packaging of products.

Drying/ Dehydration of fruits and vegetables

Drying or dehydration is a preservation method that involves removing water from fruits and vegetables to reduce their moisture content. By eliminating water, microbial activity is inhibited, enzymatic reactions are slowed down, and the shelf life of the produce is extended. This process is crucial in post-harvest management to prevent spoilage and maintain the nutritional value of fruits and vegetables. Let's delve into the concept and methods of drying/dehydration using easy vocabulary:

Concept of Drying/Dehydration:

Drying is a traditional preservation method that dates back centuries. The main idea is to remove water from fruits and vegetables, which inhibits the growth of microorganisms responsible for spoilage. The process concentrates the flavours and nutrients present in the produce, making it lightweight and easy to store. Dried fruits and vegetables have a longer shelf life, allowing consumers to enjoy them beyond the harvest season.

Methods of Drying/Dehydration:

Various methods are used for drying fruits and vegetables, each suited to different produce and scale of operation. The common methods include:

1. Sun Drying: Sun drying is the most ancient and straightforward method. Fruits and vegetables are spread out in the sun on clean surfaces or drying racks. The heat from the sun evaporates the water content over time. However, sun drying may not be suitable in humid or rainy climates and can lead to contamination.
2. Solar Drying: Solar drying is an improved version of sun drying, using specially designed solar dryers. These devices capture solar energy to create a controlled and more hygienic drying environment. Solar dryers are particularly useful in areas with abundant sunlight.
3. Air Drying: Air drying involves placing produce in a well-ventilated space with good air circulation. Natural air movement facilitates water evaporation, but the process is slower compared to other methods.
4. Mechanical Drying: Mechanical drying employs equipment such as electric dehydrators, ovens, or microwave ovens. These devices regulate temperature and airflow, ensuring consistent and faster drying. Electric dehydrators are commonly used for home-based drying.
5. Freeze Drying: Freeze drying is a more advanced method used for delicate fruits and vegetables. In this process, the produce is frozen, and then a vacuum is applied to remove water by sublimation, converting ice directly into vapour. Freeze-dried products retain their shape, colour, and nutritional content.
6. Vacuum Drying: Vacuum drying involves placing the produce in a vacuum chamber where pressure is reduced. Low pressure lowers the boiling point of water, and it evaporates at a lower temperature.
7. Oven Drying: Oven drying is a simple and accessible method for home use. Fruits and vegetables are spread on baking trays and dried at a low temperature in a conventional oven. Care should be taken to prevent over-drying, which can lead to loss of flavour and nutrients.
8. Microwave Drying: Microwave drying is a quick method that uses microwaves to heat the produce. It is essential to monitor the process to avoid uneven drying.
9. Dehydrator: A food dehydrator is an appliance designed specifically for drying fruits and vegetables. It has trays where you place the produce, and it circulates warm air to dry them evenly.

Preparation before Drying:

Before drying, fruits and vegetables are often pre-treated to improve the drying process and the quality of the final product. Common pre-treatments include blanching (briefly boiling produce in water) to inactivate enzymes and improve colour retention, sulfuring (exposure to sulfur dioxide gas) to prevent browning, and dipping in sugar syrup to enhance sweetness.

1. Preparation: Wash and peel (if needed) the produce. Cut them into uniform pieces to ensure even drying.

2. Blanching: Some foods benefit from blanching – briefly boiling and then cooling in ice water. This helps preserve color and texture.

3. Arrangement: Place the pieces on drying trays in a single layer. Make sure they're not too close together to allow proper airflow.

4. Drying Process: Depending on the method, you'll need to keep the temperature low and consistent. Check regularly and rotate trays if needed.

5. Testing for Dryness: Fruits and vegetables are dry when they feel leathery and brittle, without any moisture. You can also test by trying to bend a piece – it should snap without being rubbery.

6. Cooling: Allow the dried produce to cool before packaging. Store them in airtight containers in a cool, dry place.

Drying or dehydration is a valuable post-harvest management technique that extends the shelf life of fruits and vegetables, preserving their nutritional value and flavours. The choice of drying method depends on factors such as available resources, climate, and scale of operation. By properly drying fruits and vegetables, we can enjoy their goodness beyond the harvest season and reduce food waste, contributing to sustainable and efficient post-harvest practices.

Osmotic drying

Osmotic drying is a unique and innovative method of removing water from fruits and vegetables by immersing them in a hypertonic solution. Unlike traditional drying methods that use heat to evaporate water, osmotic drying utilizes the principle of osmosis to achieve moisture reduction. This process helps preserve the natural colour, flavour, and nutrients of the produce, making it an attractive option for post-harvest management and value addition.

Concept of Osmotic Drying:

Osmosis is a natural process in which water moves from an area of lower solute concentration to an area of higher solute concentration through a semi-permeable membrane. In osmotic drying, fruits or vegetables are immersed in a hypertonic solution (one with a higher concentration of solutes, typically sugar or salt) to create a concentration gradient. Water from the produce moves out through the semi-permeable membrane, drawn by the higher solute concentration in the solution. As a result, the water content of the produce decreases without subjecting them to high temperatures, preserving their quality.

Osmotic Drying Process:

The osmotic drying process typically involves the following steps:

1. Preparation of Solution: A hypertonic solution is prepared by dissolving sugar or salt in water. The concentration of the solution depends on the type of produce and the desired level of moisture reduction.
2. Pre-treatment: The fruits or vegetables are usually pre-treated by washing and peeling (if necessary) to remove any surface contaminants and improve the efficiency of osmotic drying.
3. Osmotic Dehydration: The produce is then immersed in the hypertonic solution, and the container is covered to prevent contamination. Osmotic dehydration takes place over a period of time, during which water moves out of the produce into the solution.
4. Rinsing: After the desired level of moisture reduction is achieved, the produce is removed from the solution and rinsed to remove excess solutes.
5. Drying/Finishing: Osmotically dried fruits and vegetables may undergo further drying to achieve the desired texture and moisture level. This can be done using traditional drying methods like air drying or freeze drying.

Benefits of Osmotic Drying:

• Preservation of Nutritional Value: Osmotic drying occurs at lower temperatures compared to traditional drying methods, which helps retain the heat-sensitive nutrients of the produce.
• Improved Quality: Osmotic drying helps preserve the natural colour, flavour, and aroma of fruits and vegetables, making them more appealing to consumers.
• Reduced Processing Time: Osmotic drying can be faster than some traditional drying methods, especially when used as a pre-treatment before final drying.
• Cost-Effectiveness: The osmotic drying process does not require expensive equipment, making it a cost-effective option for small-scale operations.
• Extended Shelf Life: Osmotically dried fruits and vegetables have reduced water activity, leading to a longer shelf life and reduced susceptibility to spoilage.

By harnessing the power of osmosis, osmotic drying provides a gentle and effective way to remove water from produce, resulting in high-quality, nutritious, and shelf-stable products. Its potential in post-harvest management and value addition makes it an exciting avenue for the food industry.

Canning - Concepts and Standards

Canning is a popular method of preserving food items, including fruits, vegetables, meats, and seafood, by sealing them in airtight containers and subjecting them to heat to destroy spoilage-causing microorganisms. The canning process ensures the long-term shelf stability of the products while retaining their nutritional value and flavour.

Concepts of Canning:

1. Preservation through Heat Treatment: Canning involves heating food items in hermetically sealed containers to kill or inactivate microorganisms, including bacteria, yeasts, and moulds. This heat treatment prevents the growth of spoilage and pathogenic microorganisms, thus preserving the food for extended periods.
2. Airtight Sealing: Canning containers, typically made of metal or glass, are sealed tightly to prevent the entry of air and microorganisms. This airtight sealing creates a barrier that keeps the food safe from contamination.
3. High-Temperature Processing: Canned products are subjected to high temperatures during processing. This thermal treatment destroys enzymes that can lead to deterioration and inactivates harmful microorganisms, ensuring the safety and quality of the canned items.
4. Vacuum Sealing: In the canning process, a vacuum is created inside the container, which helps to remove air and reduce the oxygen level. This reduces the risk of oxidative reactions that could lead to food spoilage.
5. Extended Shelf Life: Properly canned products can have a long shelf life, allowing consumers to enjoy seasonal fruits and vegetables throughout the year and reducing food waste.

Canning Standards:

To ensure the safety and quality of canned products, various standards and guidelines are followed:

1. Good Manufacturing Practices (GMP): Canning facilities must adhere to GMP, which includes maintaining hygienic conditions, employing trained personnel, and using appropriate equipment.
2. Heat Processing Time and Temperature: Specific time and temperature combinations are employed during the heat treatment to achieve adequate sterilization and kill harmful microorganisms.
3. pH Control: For certain low-acid foods, such as vegetables and meats, the pH level is adjusted to ensure the safety of the canned products.
4. Container Integrity: Cans and jars must be free from defects, such as dents or cracks, to ensure a proper seal and prevent leakage or contamination.
5. Labelling and Traceability: Canned products must have accurate and informative labels, including the product name, ingredients, manufacturing date, and storage instructions. Traceability measures are implemented to identify the source of ingredients in case of any quality issues.

Packaging of Canned Products:

Canned products are typically packaged in:

1. Metal Cans: Metal cans are commonly used for canning fruits, vegetables, meats, and seafood. They are sturdy, provide excellent protection from light and air, and are easily recyclable.
2. Glass Jars: Glass jars are preferred for canning products like jams, jellies, and sauces. They allow for a transparent view of the contents and are reusable for home canning.
3. Sealing Lids: Airtight sealing lids, usually made of metal or plastic, are used to close the cans or jars securely.

Types of containers 

There are different types of containers that can be used for canning, depending on the food and the design. Some of the common containers are:

• Steel cans. These are metal containers that are strong and can handle high heat and pressure. They are coated with tin or chromium to prevent rusting. Steel cans are used for many foods, such as fruits, vegetables, meats, soups, sauces, and drinks.
• Aluminum cans. These are metal containers that are light and can also handle high heat and pressure. They are made by shaping a piece of metal into a cylinder with a round end. Aluminum cans are mainly used for drinks, such as soft drinks, juices, beer, and wine.
• Glass jars. These are clear containers that can show the color, taste, and nutrients of food. They are made by melting glass into different shapes and sizes. Glass jars are used for foods that need low to medium heat to preserve them, such as jams, pickles, honey, and sauces.
• Plastic containers. These are flexible containers that can be made into different shapes and sizes. They are made from different kinds of plastic materials, such as PET, PP, or PS. Plastic containers are used for foods that do not need heat to preserve them, such as salads, dips, spreads, and dairy products.

The process of heat treatment, airtight sealing, and adherence to established standards ensure that canned products retain their nutritional value and taste while remaining free from harmful microorganisms. Proper packaging further contributes to the protection and longevity of canned foods, making them a valuable addition to post-harvest management and enhancing food availability throughout the year.

Packaging of Products

Packaging plays a crucial role in various industries, including food, pharmaceuticals, electronics, and more. It involves designing and creating protective and attractive containers for products, ensuring their safety, preservation, and market appeal. Proper packaging is essential for post-harvest management, value addition, and delivering products to consumers in optimal condition. Let's explore the importance and aspects of packaging products:

Importance of Packaging:

Product Protection: Packaging serves as a protective barrier against physical damage, moisture, light, air, and other external factors that can affect the quality and shelf life of the product.

Preservation and Freshness: Packaging helps preserve the freshness, flavour, and nutritional value of perishable goods like fruits, vegetables, and dairy products by creating a controlled environment.

Safety and Hygiene: Proper packaging ensures that products reach consumers in a safe and hygienic condition, reducing the risk of contamination and ensuring consumer confidence.

Brand Identity and Marketing: Packaging plays a significant role in establishing a brand identity and influencing consumers' purchasing decisions. Attractive and well-designed packaging can enhance a product's market appeal.

Convenience and Portability: Packaging provides convenience in handling, storage, and transportation of products, making it easier for consumers to use and carry them.

Aspects of Packaging:

Materials: Packaging materials vary depending on the product type, shelf life, and intended use. Common materials include cardboard, plastic, glass, metal, and flexible packaging like pouches and wrappers.

Design and Graphics: Packaging design includes shape, size, and visual elements like logos, images, and colours that communicate the product's identity and brand message.

Protection and Safety Features: Packaging may include safety features like tamper-evident seals, child-resistant closures, and barrier properties to ensure product integrity and consumer safety.

Labelling and Information: Product labels provide essential information such as product name, ingredients, nutritional facts, manufacturing date, expiry date, and usage instructions.

Sustainability: Eco-friendly and sustainable packaging options, such as biodegradable materials and recycling symbols, are becoming increasingly important to address environmental concerns.

Functional Features: Packaging may include handles, resealable closures, or easy-to-open designs, enhancing convenience for consumers.

Packaging method:

Selection of fruits and vegetables (removal of damage, infected etc fruits and vegetables) → Remove inedible portion before packaging→ Washing in water → Remove adhering water→ Pack loose and fresh

Linners: These are the cushioning materials used to prevent scratches or damage of fruits surface while packing the produce in baskets and wooden boxes. These are newspapers, paddy straw, dry grasses, fruit plant leaves, saw dust etc.

Wrapping: Covering the fruits after harvest with any material in order to improve it post harvest life.

Function of wrapping:

• To provide support and stop entry of foreign materials
• To protect from mechanical and environmental hazards
• To assists sale (retailers and consumers).

Qualities/Characteristics of an ideal package:

• It should be contain the content within it.
• Not affect the flavor of the product packed inside of it.
• Stable performance over large range of temperature
• Adequate compulsive strength and sufficient impact and puncture strength.
• Sufficient thickness of cushioning materials with sufficient ventilation
• Sufficient space for rapid cooling of contents
•  Protect the content from oxygen, moisture and light.
• Compatible to the food product
• Protection of the content from adulteration
• Closure characteristics such as opening, sealing, resealing and pouring
• Proper labelling, strong marketing appeal to promote the sale of food product
• Low cost and availability
• Biodegradability and recyclability.

Types of Packaging Materials 

1. Paper and Cardboard:
   • Corrugated Boxes: Sturdy and versatile, corrugated boxes offer protection and can be customized for different sizes and weights.
   • Cartons: Used for food items, cosmetics, and other products, cartons are made from paperboard and often include printed graphics for branding.
   • Paper Bags: Lightweight and eco-friendly, paper bags are used for groceries, gifts, and takeout items.
2. Plastics:
   • PET (Polyethylene Terephthalate): Used for water bottles, soft drink containers, and food packaging due to its transparency and durability.
   • HDPE (High-Density Polyethylene): Commonly used for milk jugs, detergent bottles, and other household products.
   • LDPE (Low-Density Polyethylene): Used for flexible packaging like plastic bags and shrink wrap.
   • PP (Polypropylene): Used for food containers, yogurt cups, and bottle caps due to its heat resistance and durability.
   • PS (Polystyrene): Used for disposable cutlery, CD cases, and foam packaging.
   • Flexible Plastics: Used for stand-up pouches, snack packaging, and resealable bags.
3. Glass:
   • Bottles and Jars: Commonly used for beverages, sauces, jams, and cosmetics due to its inert nature that doesn't affect flavor or aroma.
4. Metal:
   • Aluminum Cans: Widely used for beverages like soda and beer due to their light weight and protection against light and air.
   • Steel Cans: Used for canned goods like vegetables, soups, and meats due to their durability and protective properties.
5. Flexible Films:
   • Polyethylene Films: Used for items like bread bags, produce bags, and trash bags.
   • Polypropylene Films: Used for snack packaging, frozen food bags, and microwaveable packaging.
   • Vacuum-Sealed Bags: Used for perishable products to remove air and extend shelf life.
6. Composite Materials:
   • Tetra Pak: Combines paper, aluminum, and plastic to create cartons suitable for liquid products like milk, juice, and soups.
   • Aseptic Packaging: Combines plastic and metal layers to create shelf-stable packaging for liquids, sauces, and dairy products.
7. Biodegradable and Sustainable Materials:
   • Bioplastics: Made from renewable resources like cornstarch or sugarcane, offering an eco-friendly alternative to traditional plastics.
   • Paper-based Packaging: Includes compostable trays and containers for food items.
   • Plant-Based Packaging: Made from materials like bamboo, palm leaves, or coconut shells, providing sustainable options for various products.
8. Specialty Materials:
   • Foam Packaging: Used for fragile items like electronics to provide cushioning and protection.
   • Bubble Wrap: Provides protection for delicate items during shipping.
   • Vacuum-Sealed Pouches: Used for coffee and perishable goods to preserve freshness.

Choosing the appropriate packaging material depends on factors such as product characteristics, shelf life, transportation requirements, sustainability goals, and consumer preferences. Selecting the right material ensures that products are protected, well-presented, and aligned with branding objectives.

Innovations in Packaging:

Advancements in packaging technology have led to various innovative solutions, such as:

Active Packaging: Incorporating materials that interact with the product to extend shelf life, like oxygen absorbers or moisture control agents.

Smart Packaging: Using technologies like QR codes and NFC tags to provide consumers with additional product information or interactive experiences.

Edible Packaging: Creating packaging materials from edible substances to reduce waste and enhance sustainability.

Modified Atmosphere Packaging (MAP): Adjusting the gas composition inside the package to extend the freshness of perishable foods.

MAP

Modified Atmospheric Packaging (MAP) is a technology used in packaging to extend the shelf life of perishable products by modifying the composition of gases within the packaging environment. The primary goal of MAP is to slow down the deterioration of food items, thereby preserving their freshness and quality. Here's a simple breakdown of the concept:

1. Principle: Modified Atmospheric Packaging involves changing the composition of gases (such as oxygen, carbon dioxide, and nitrogen) within a package to create an environment that inhibits the growth of spoilage microorganisms and slows down enzymatic reactions responsible for food deterioration.
2. Benefits: MAP offers several benefits, including:
   • Extended Shelf Life: By controlling the gases, MAP can significantly prolong the time before food becomes spoiled.
   • Improved Quality: MAP helps maintain the color, flavor, texture, and nutritional content of the packaged product.
   • Reduced Need for Additives: With longer shelf life, there's less reliance on chemical preservatives.
   • Reduced Food Waste: Products stay fresher for longer, reducing the likelihood of products being discarded due to spoilage.
3. Common Gases Used:
   • Oxygen (O2): In some cases, reducing oxygen levels can slow down oxidative reactions that lead to spoilage and discoloration.
   • Carbon Dioxide (CO2): Elevated levels of carbon dioxide can inhibit the growth of certain spoilage microorganisms and help maintain product color.
   • Nitrogen (N2): Nitrogen is often used to displace oxygen, creating an atmosphere with reduced oxygen levels that retards spoilage and prevents oxidation.
4. Applications:
   • Fresh Produce: MAP is commonly used for fruits, vegetables, and salads to maintain freshness and extend shelf life.
   • Meat and Seafood: MAP helps preserve the color and texture of meat and seafood while inhibiting microbial growth.
   • Bakery Products: MAP can prevent staleness and mold growth in baked goods.
   • Dairy Products: Products like cheese, yogurt, and milk benefit from MAP's ability to extend freshness.
5. Packaging Process:
   • The product is placed in a container or package.
   • The atmosphere within the package is adjusted by introducing the desired gases.
   • The package is then sealed, creating a controlled environment.
6. Considerations:
• Proper gas composition and packaging materials are crucial to achieving the desired shelf life extension.
• Monitoring and controlling gas levels within the package require precision to ensure effectiveness.
• Microbial contamination can still occur if not properly managed, so good hygiene practices remain essential.

Type of MAP:

1. Passive MAP: Passive MAP involves adjusting the composition of gases within a package and then sealing it. Once sealed, the gases within the package interact naturally with the product and its environment. Passive MAP does not involve ongoing adjustments or interventions after sealing. This method relies on selecting the appropriate gas mixture and packaging materials to achieve the desired shelf life extension. Passive MAP is suitable for products with relatively stable respiration rates and minimal sensitivity to changes in the packaging atmosphere.
2. Active MAP: Active MAP, also known as dynamic MAP, involves ongoing monitoring and adjustment of the gas composition within the package. This is typically achieved using specialized equipment and sensors. If the gas composition inside the package deviates from the desired levels, active MAP systems can automatically introduce the required gases or remove excess gases to maintain the optimal atmosphere. Active MAP is especially useful for products with varying respiration rates or those that are sensitive to slight changes in gas levels. This method offers more precise control over the packaging environment and can lead to longer shelf life.

📚 For comprehensive notes on other chapters of rainfed and dryland agriculture, please visit the website Agricorn - Post-harvest Management and Value Addition of Fruits and Vegetables.