The Aerosol Package Basically Holds the Key to Ease of Dispensing of Lemon Juice with The

AKHILESH PANDEY

Introduction

My major objective is to utilize pressurized cans for ease in dispensing of the lemon juice. The juice can be obtained from lemon fruit through cutting and mechanical pressing unit operations. This juice when added with preservative and additives is ready for packaging in the aerosol container. In this project, I will design the pressurized container for the packaging of the lemon juice. The aerosol package basically holds the key to ease of dispensing of lemon juice with the help of propellant pressurized in a metal container. The need of using a new package form is due to problems faced in even distribution of lemon juice on the food. We mostly use lemon juice on salads and numerous exotic food dishes to enhance flavor all over the world. The desired effect is to provide flavor enhancement to the food. The conventional containments used for dispensing lemon juice are glass bottles or squeezable plastic bottles. In both of the packages the uniformity of lemon juice on food surface is not ensured. That may require further mixing of food for lemon juice to evenly cover the whole food surface.

In many countries the usage of lemon juice as daily edible flavoring item is common. The problem with the usage of the lemon juice can only be dealt out through a better packaging container which may make the dispensing of the product easier. The spray cans usage for food product is catching trend lately. The answer is aerosol packaging in which different type of spray and misting of the liquid is possible. This will make the finished product more attractive and easy for the consumers to use.

Thus the problem is solved using this new idea of using pressurized spray can for packaging of lemon juice. The another term for pressurized can is aerosol can which can be defined as “An aerosol is a self pressurized packaging consisting of a metal or glass container having an attached valve that, when activated, dispenses liquid products or fine suspensions in spray, streams, gels, foams, lotions, or gases”. I may differentiate the Aerosol containers from other conventional containers which are namely plastic and glass with the help of a table 1 in the appendix considering various requirements fulfilled by the packages.

Principle of operation

When the valve is closed the gasket prevents the flow of concentrate and liquid propellant mix (under pressure) by sealing the valve stem at orifice and the shoulder. The valve opens when the actuator button is depressed against spring tension, flexes the gasket, and exposes the stem orifice to internal pressure, forcing concentrate and liquid propellant mix through he orifice in the valve stem and finally through the button. The diagram for the open and closed valve conditions is displayed in figure 1 of appendix.

The Design

I will explain here the basic criteria of designing an aerosol container for the packaging of the lemon juice. In my design I have considered the standard rules and selection criteria for the design. The product to be filled in is to be considered first before a package can be designed. The lemon juice is an aqueous solution having composition in table 2 of appendix.

Our main consideration during aerosol packaging will be the lemon juice interaction with the propellant and the inner body of the packaging material used. From the table 2 in the appendix, we can see that the amount of organic acid content of lemon can cause problem of pitting or stripping. Therefore a design is made upon considering numerous variables for packaging of any sort of product in aerosol packages. The best approach is to start with consideration of the product formula. The points to be considered are that the product is miscible into the propellant; will it form a separate layer. The propellant used must be a liquefied or a compressed gas. The type of formulation also decides the filling method of the product. The product and propellant can either be cold filled. Other method is UTC (under the cup) method and pressure filling method. The main objective is to use the best one for the packaging of the lemon juice. The type of spray must be considered for desired product output. This depends upon the combination of the valve and the actuator. The control of spray type is done by choosing the proper orifice sizes and taper in the actuator button, the valve stem, the percent of propellant used, and the tail piece. The valve must be compatible with the lemon juice. The material of the container may be either of aluminum, steel or glass. This depends upon the cost as well as the strength required after pressurization of the can. This is where the real designing of the aerosol package for lemon juice packaging starts with the selection of best suited materials and method for design of whole package.

The Selection Criteria

There is multiple numbers of objectives to be fulfilled side by side as the pack is designed by selecting the most optimum package component for the desired packaging.The objectives are summed up as:

1. The type of container
2. The type of spray required
3. The type of propellant

1. The type of containers

The types of material available for the container are Steel, Aluminum and Glass. A best suited container is sorted out from the materials strength. The product to package interaction, economics and variety of sizes available in the market. The table3 in the appendix shows the various properties of the materials. One can easily sort out the best material for packaging of the lemon juice. The Steel is the most cost effective and can bear the pressure inside the can. The standard sizes of steel are also available in highest number in the market. Therefore I choose steel as the packaging material for the lemon juice aerosol package. The table for the material of container selection according to the properties of the Aluminum, Steel and Glass is provided in the table 3 of the appendix.

1. The type of spray required

This selection criterion for the spray is the most complex and depends upon the following:

1. Valve and Actuator combination

2. Valve stem

1. Tail piece

Three orifices

1.Body orifice

2.Stem orifice

3.Vapor tap

Valve

The primary purpose of the valve is to control the flow of the product out of the container when it is needed and to prevent any discharge when it is not wanted.

Actuator

There are many types of actuators depending on the purpose of usage with different type of mouth openings.

(The valve and actuator assembly is provided in the figure 2 of the appendix.)

Over-cap

To protect the valve from accidental discharge and to keep the dust and dirt away from the whole mechanism.

Dip tubes

It is generally made of PE and usually is cut to the length that reaches almost the bottom of the container. It also contributes to the quality of the final product.

Vapor Tap

A vapor tap hole in the side of a valve body which helps small amount of propellant to escape into the valve and mix with the product as it is dispensed, helps break spray into a fine mist and will be useful for use with lemon juice as it is a aqueous product. The vapor tap is used when the spray is intended to coat the surface rather than remain suspended in the air will need large droplets above 0.002 in (51.3 µm) in diameter.

Gaskets

The whole valve assembly is attached with gasket to the container with minimum set standard critical dimensions.

These gaskets are of three types:

1. PE Sleeves.
2. Cut Gaskets.
3. Laminates.

In case of lemon juice can filled with nitrogen propellant, PE sleeves may prove to be the best gaskets due to its low GTR values. These assumptions are made through values in the tables available in Handbook of packaging by Gordon.

The type of spray is controlled by the above factors by changing the critical dimensions used for the above parts of the valve and actuator assembly.

The Critical Dimensions

The standard dimensions are used while choosing the different parts for the metal cans. These dimensions are strictly according to rules and regulations. The ranges and combination variation runs into thousands of the eighty or so manufacturers. The figure for the critical dimension is provided in the appendix as figure 3.

3. Type of Propellant

There are three broad class of propellant. These are:

1. Hydrocarbons: These are highly flammable propellants like butane isobutene, propane and DME used particularly with water based products but can also be used for many solvent based products. Extreme high caution must be taken while use and storage of hydrocarbon propellants. They exert a pressure of 17-110 psig at room temperature. They are low in cost but I have not chosen hydrocarbons as the propellant for my lemon juice aerosol container due to risk in filling and handling.
2. Hydroflurocarbons:These are very good propellants which can be used with low miscibility and toxicity to the product. The most common ones are safe to breathe at a concentration of 1000 ppm. Some of the hydro fluorocarbons are CFC, HFC-134A, HFC-152A, etc. They are a threat to the ozone layer of the atmosphere and their use is reduced with time. They can be readily blended in different combinations with the hydrocarbons but the cost is high.
3. Compressed Air: This is the best propellant for use in my project. Different inert gases like nitrogen, carbon dioxide and nitrous dioxide provide very good propulsion to the product and can be loaded upto pressure of 100 psig. The table for comparison of these gases is provided in the appendix as table 4. The nitrogen comes out to be the best option since it is nearly insoluble and very easily filled in the container. The filling of nitrogen is done by injecting a liquid drop in the open metal can and then replacing the valve actuator assembly. The headspace within the can is 25% as the standard criteria for nitrogen based propellant product combinations.

How much pressure is to be kept?

The required pressure and amount of Nitrogen to be filled can be calculated very easily by Boyle’s law, Charle’s law, Avogadro law and Raoult’s law which are stated as follows:

Boyle’s Law: According to Boyle’s law the pressure of gas varies as the inverse of the volume and conversely the volume varies with inverse of the pressure

P initial / P final = V final / V initial

Charles Law: It indicates that for a fixed amount of gas (fixed number of moles) at a fixed pressure, the volume is proportional to the temperature.

V/T = constant or V1/T1 = V2/T2

In other words, as the temperature increases, the volume increases.

Avogadro’s Law: At a constant temperature and pressure, the volume of a gas is directly proportional to the number of mole of a gas at 1 atm and 32oC of that gas is 22.4 liters. Mathematically, this can be represented as:

Volume (V) = Constant (K) x Moles (n)

Raoult’s law: It states that the vapor pressure of each component in an ideal solution is dependent on the vapor pressure of the individual component and the mole fraction of the component present in the solution.

Once the components in the solution have reached chemical equilibrium, the total vapor pressure of the solution is:

Psolution = (P1)pureX1+(P2)pureX2…

and the individual vapor pressure for each component is

Pi = (Pi)pureXi

Where;

(Pi) pure is the vapor pressure of the pure component

Xi is the mole fraction of the component in solution

Conclusion

The recommendations and specifications for the complex dimensions of aerosol container and critical tolerances to cover all orifices, type of gasket material and stem and body material. Other specifications are the tube dimension, actuator type, orifice size and valve cup coatings are published by the chemical specialty manufacturer association (CSMA) D10 of ASTM (American Society for Testing and Materials). According to the packaging criteria for lemon juice the size of containment will allow us to calculate the amount of propellant required inside the can.

APPENDIX

The table for comparison of requirement for different container materials.

TABLE 1

Serial# / Requirements / Aerosol can / Plastic bottles / Glass containers
1 / Specific amount of lemon juice delivery / Yes / Yes / No
2 / Control pattern and size of the drop/mist particle of lemon juice / Yes / No / No
3 / Sanitary / Yes / No / No
4 / Tamper resistant / Yes / Yes / Yes
5 / Easy to use / Yes / Yes / No
6 / Environmentally sound / Yes / No / Yes
7 / Cost Effective / No / Yes / No

Table defining the properties of lemon juice

TABLE 2

Lemon juice

• Food number: 11557
• Scientific name: Citrus limon
• Food type: Food
• Processing method: Mashed
• Ingredient class: Juices
• Food use class: Juices
• Edible proportion: 100%
• Special diets

/

Energy content

fat, total / 0%
Protein, total / / 6%
carbohydrate, available / / 30%
alcohol / 0%
organic acids, total / / 64%
sugar alcohols / 0%
Properties / Steel / Aluminum / Glass
Bursting Strength
@130 Fahrenheit (equal gauge for steel and aluminum) / 1067 M Pa / 2170 M Pa / ≈ 1.5 times the pressure of the content
Product vs. Container interaction / Non reactive / Reactive / Non Reactive
Cost per 1000 container / 120-130$ / 200-700$ / 250-750$
Standard sizes available / 10 / 8 / 6

The table for properties comparison of steel aluminum and glass.

TABLE 3

The table for cost comparison of different propellants

TABLE 4

Type / Cost
Hydrocarbons / 0.250$/lb truck load delivered
Compressed gas / 0.500$/lb truck load delivered
Hydro fluorocarbon / 1.50$/lb truck load delivered

The valve open and closed conditions of a spray can.

FIG 1

The main valve-actuator assembly unit and its various components

FIG 2

The critical standard dimensions for the valve actuator assembly.

FIG 3

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