Course:FNH200/Projects/2021/Orange Juice (not from concentrate)

Orange juice without pulp.

Introduction

Orange juice is the liquid extract of squeezed oranges and may include orange pulp pieces. Orange juice products usually derive from four main groups of oranges: China oranges, Seville oranges, mandarin oranges, and hybrid oranges. 70 million tonnes of oranges are produced globally per annum and around one-third is turned into juice.

Orange juice is commonly sold as “from concentrate” or “not from concentrate.” “From concentrate” orange juice goes through a water extraction process required for transportation post-processing. Before being packaged and sold, water is added back into the concentrated juice and then pasteurized. “Not from concentrate” orange juice is simply squeezed, then pasteurized.

Manufacturing

Orange juice with pulp.

When oranges are mature and ready to be picked, they are harvested from orange trees and transported to a juice extraction facility. The oranges will be cleaned and graded after inspection. The certified fruit is transported onto a conveyor for cleaning and sorted based on their size for extraction. Next, juice is extracted. Proper extraction is essential to optimize the quality and amount of juice extracted. There are two common methods used by the industry for extraction. The first places the fruit between two metal cups with sharpened metal tubes at their base. The upper cup descends and the fingers on each cup mesh to express the juice as the tubes cut holes in the fruit. The second slices oranges as they pass by a stationary knife and the halves are picked up by rubber suction cups and moved against plastic serrated reamers to extract juice. The extracted juice is chilled or concentrated before reconstitution. Concentration produces many varieties of orange juice, increases shelf life of orange juice, and makes shipping and storage more economical. When diluted with water, concentrated juice is made into ready-to-drink beverages and frozen juices. In reconstitution, concentrate is pulled from several storage batches and blended with water to achieve the desired sugar to acid ratio, colour, and flavour. Pulp may be blended back in to create orange juice with pulp. Orange juice is pasteurized to curtail spoilage. Finally, the juice is filled and packaged. The juice is hot when being filled into the containers to enforce sterility. Byproducts such as orange pulp is processed to be sold as pulp and livestock feed, and pectin is used to make citric acid, essential oils, etc.

Pulp vs. No Pulp

A hydrocyclone diagram. The purple arrow is where the pulp slurry enters the hydrocyclone, the red arrow is where the defect pulp exits the hydrocyclone, and the green arrow is where the acceptable pulp exits the hydrocyclone.

After extraction, there is still pulp in the juice. This pulpy juice is filtered through two finisher screens to separate the pulp and juice. There are two types of finisher screens, either using a screw or spinning paddles pressed against a screen, and the holes in the screen controls how much pulp remains in the juice. The pulp slurry is washed in multiple stages and a hydrocyclone removes the defect pulp. The pulp then goes through heat treatment to kill relevant microorganisms and inactivate enzymes that would cause the pulp and juice to separate in the final product. After pasteurization, the pulp is clarified and passes through a polymeric resin bed to absorb limonin, a complex compound that imparts a bitter taste, out of the pulp. The debittered pulp goes through evaporator feed tanks and an evaporator before being blended back into juice to create orange juice with pulp. Pulp is not blended into orange juice that is meant to be without pulp.

Regulations in Canada

The Foods and Drugs Regulations of Canada requires orange juice to be made from clean, sound, and mature oranges. Chemical analyses are conducted to determine if the orange juice follows regulations. Orange juice must have at least 1.20 milliequivalents of free amino acids, 115 milligrams of potassium per 100 millilitres, and an absorbance value for total polyphenolics of 0.380. Official methods FO-21, FO-22, and FO-23 are conducted to determine the milliequivalents of free amino acids, the amount of potassium, and the absorbance value for total polyphenolics in orange juice respectively. Before adding sugar, invert sugar, dextrose, or glucose solids, a Brix reading and determination of acid are conducted. A °Brix (degree Brix) scale measures sugar concentration of a pure sucrose solution to its density at 20°C. The Brix reading must be at least 9.7°C. Additionally, orange juice must contain a minimum of 0.5% and a maximum of 1.8% of acid by weight calculated as anhydrous citric acid. The chemical analyses are determined by official methods FO-24 and FO-25 respectively. Orange juice may contain orange essences, orange oils, and orange pulp adjusted in accordance with good manufacturing practice. It is also approved to contain sugar, invert sugar, dextrose in dry form, glucose solids, a Class II preservative, amylase, cellulase, and pectinase.

Flavour Packs

Orange juice manufacturers do not disclose any information regarding the use of flavour packs in their orange juice advertising or packaging. Orange juice marketing may be misleading as unadulterated terms like “fresh,” “pure,” “natural,” and “not from concentrate” are often used. However, orange juices are pasteurized, resulting in the loss of volatile compounds and, consequently, orange juice flavour. Flavour packs engineered by fragrance companies using orange extracts are added to juice to produce the consistent smell and taste of orange juice that consumers are familiar with. Flavour packs are not created chemically in a lab but from a physical process of boiling orange peels to capture the volatile compounds that were lost during pasteurization. Adding flavour packs is allowed in Canada, but the Canadian Food Inspection Agency states that orange juice manufacturers who use flavour packs should label their products as "orange juice added with flavour." When orange essence or oil is used for flavouring, the manufacturer must label their product to indicate the added flavour and the amounts of oil added. Different manufacturers make different adjustments to their flavour packs to create their own orange juice flavour.

Carton Packaging vs Plastic Packaging

PETE orange juice bottle (Tropicana No Pulp Orange Juice)

In Canada, Division 23 of the Food and Drugs Act and Regulations controls the safety of food packaging. Section B.23.001 of which prohibits the sale of foods in packages that may impart any substance to the contents which may be harmful to the consumer of the food.

Plastic Bottles

Plastic bottles are a common type of orange juice packaging used. For example, Tropicana Orange Juice bottles are made of PETE (Polyethylene Terephthalate, also abbreviated as PET). PETE is an approved food packaging material by Health Canada.

Aroma Barrier

PETE is a polar polymer and a good aroma barrier against non-polar aroma compounds like d-limonene but may not be as effective against polar aroma compounds like ethyl butanoate (by the chemical principle “like dissolves like”). However, a study found that the loss of major aroma compounds in orange juice through packaging material was insignificant compared to loss through the cap (sealing).

Oxygen Barrier

PETE does not prevent oxygen permeation very well as the small oxygen molecules can fit through the pores in the polymeric structure of PETE. To reduce oxygen permeability, extra oxygen barriers (oxygen scavengers) are usually added to the bottles to prevent oxygen permeation.

Light Barrier

Refrigerated carton of orange juice (Minute Maid Original Orange Juice)

PETE does not prevent light transmission as it is transparent. However, light has minimal impact on orange juice deterioration (mainly vitamins) without the presence of oxygen.

Refrigerated Cartons

Refrigerated cartons are another common type of orange juice packaging and made of three layers: PE (polyethylene) — paper board — PE, distinguished from shelf-stable Tetra Paks which are made of PE — paper board — PE — aluminium foil — PE. PE is an approved food packaging material by Health Canada.

Aroma Barrier

PE is a non-polar polymer and a poor aroma barrier against non-polar aroma compounds in orange juice like d-limonene but may be more effective against polar aroma compounds like ethyl butanoate (by the chemical principle “like dissolves like”). Additional aroma oils may be added to compensate for aroma compound loss.

Oxygen Barrier

The PE foils and paperboard themselves are not a good oxygen seal as small oxygen molecules can fit through the pores in their microscopic structure. So, it is common to add an additional oxygen barrier layer (usually EvOH, ethylene vinyl alcohol) to prevent oxygen permeation. The quality of the oxygen barrier depends on the tightness of two different types of sealing of the cartons: longitudinal seal is the insulation between the layers of the carton, which is done by heat sealing, and transversal seal is completed after filling to seal the carton from the outside environment. This creates either no-headspace or oxygen-free headspace packaging; either way, oxygen is removed from the package.

Light Barrier

The paper board in between the PE layers provides physical stability and a light barrier to some extent.

Exam Question

Why is polyethylene terephthalate (PETE) a poor oxygen barrier for orange juice?

1. Oxygen reacts with PETE and produces a toxin
2. Oxygen molecules are small enough to fit through the pores on PETE's polymeric structure
3. PETE is polar while oxygen is non-polar, different polarities attract each other
4. PETE is polar while oxygen is non-polar, so PETE is actually a good oxygen barrier

Correct answer = 2.

Explanation for each option:

1. PETE does not react with oxygen under normal conditions, otherwise it won't be considered as a safe food packaging material by Health Canada.
2. Oxygen molecules are smaller than the liquid and aroma molecules, so it can physically fit through the pores in PETE's polymeric structure, similar to sands falling through a sieve while stones get blocked.
3. Polar and non-polar in chemistry differs from positive and negative polarities in electromagnetism, so "different polarities attract each other" does not apply here.
4. By "like dissolves like,” polar substances indeed have poor solubility with non-polar substances. However, the permeation of oxygen is a physical process that does not involve dissolving.

This question should be on the final because Module 8.7 discussed the importance of oxygen in food preservation, so it is good to know the principles behind oxygen permeation in food packaging.