They teams from the University Miguel Hernandez in Alicante and the San Antonio Catholic University in Murcia published their findings in the Journal of Food Quality.
The researchers said they assessed the quality of the juice based on its high vitamin C content, intense orange colour, fresh mandarin flavour and absence of negative off-flavours.
“A container with thick inner layer of aluminium foil will maintain the quality of the juice for a longer time (over 90 days) compared with a shelf life of about 54 days from cartons with an inner layer of ethylene vinyl alcohol copolymers,” said the research group.
Fruit juices and beverages must be handled carefully during processing and storage to control nutrient losses and colour changes, and the label showing content per serving of the important nutritional component, ascorbic acid (AA), must be valid throughout the product shelf life, claim the researchers.
Permeation through packaging materials and the degradation of colour and nutrients by oxygen transmission through packages is an increasing area of research, said the group; however, they claim their study is the first evaluation of the effects of carton materials on mandarin juices
The aim of the research, said the team, was to compare the colour properties, AA degradation and changes of gas composition in the headspace of refrigerated mandarin juice stored in four different containers.
According to the study, orange juice accounts for 60 per cent of all Western European consumption of fruit juices and juice-based drinks. The team said their results can inform manufacturers regarding which container is the best for refrigerating this particular juice type.
The researchers said that juices were processed under aseptic packaging and thermal treatment of pasteurization, packaged in three different nontransparent plastic containers and one transparent container and were stored under refrigeration conditions.
Juices A and B were stored in containers made of different percentages of cardboard, polyethylene and aluminium foil, respectively, juice C was stored in containers made of cardboard, polyethylene and ethylene vinyl alcohol copolymers and juice D was stored in bottles made of polyethylene terephthalate (PET), stated the study.
The team said that the juice samples were analysed at various intervals between 0 and 90 days.
Oxygen production was measured in the juice containers, according to the scientists, by extracting 1mL of the headspace using a gas syringe, and oxygen was quantified using a Shimadzu model 14A gas chromatograph, while colour determinations were made using a Hunterlab Colour flex.
The researchers added that sensory evaluation was determined over sampling days 0 to 90 and a panel of 20 consumers was used:
"The principal selection criterion was that subjects had to be regular consumers of juice at least twice a week,” explained the team.
The consumers, said the researchers, were asked to rank the juices in terms of colour, fresh mandarin flavour, and off-flavours, and the assessors were trained to rinse their mouths with water and wait at least two minutes between samples.
The study concluded that juices C and D presented significantly higher oxygen concentrations than juices A and B:
“Cartons A and B could be considered as high oxygen barriers, while carton C and [the] PET bottle were low oxygen barriers. In our opinion, the main entrance of air into container C must be located in the joints of the upper part. However, further research is needed to find a proper explanation for these experimental findings," claim the research group.
They said that high reductions in vitamin C content in juices C and D were due to the fact that higher oxygen contents were present in these juices as compared to juices A and B.
According to the researchers, the experimental results proved that carton composition was an important quality control parameter in determining the degradation of the initial vivid orange colour of the refrigerated mandarin juices: “It seems evident that carton A provided better experimental results than cartons B and C and [the] PET bottle.”
In terms of the sensory analysis, the transparent PET bottle performed the worst - after only 18 days, the juice presented a less intense colour than the rest of the juices and its fresh mandarin flavour started to disappear after 36 days of refrigerated storage, while after 90 days it had a significantly higher intensity of off-flavours, claims the study.
However, the researchers found that after 54 days, both juices A and B presented significantly higher intensities of fresh mandarin flavour than juices C and D.
Source: Journal of Food Quality 31 (2008) 596-611Published online ahead of printEffect of packaging materials on colour, vitamin C and sensory quality of refrigerated mandarin juiceAuthors: F. Beltran-Gonzalez, A. J. Perez Lopez, J. M. Lopez-Nicolas, A.A. Carbonell Barrachina