Bottles

Glass bottles are the second most common or ange juice package used worldwide. For shelf-stable or ange juice in glass bottles, the most com mon fi lling method is hot fi lling. Aseptic fi ll ing of glass bottles at ambient tem per a ture is of minor impor- tance compared with hot fi lling. Of the package types used today for orange juice, glass bottles are normally con sid ered to have the best oxygen barrier prop er ties.

In hot fi lling, the deaerated and heated juice is di rect ly poured into cleaned bottles that are capped. The fi ll ing tem per a ture is usually be tween 90 °C and 98 °C; the holding time may vary be- fore the bot tle is cooled in a tunnel. Preheating of glass bot tles is necessary before fi ll ing in order to re duce the risk of glass splin ter ing.

The hot product sterilises the inside surface of the bottle, whereas bottle closures should be ster i lised before they are applied to the bottle. Prior to clo sure the bottle neck is fl ushed with

Fig. 9.14 Glass bottles. Fig. 9.13 Carton-based packages made from rolls.

9.6 Different packages and packaging systems

steam. Steam injection keeps foaming to a min- i mum, reduces the oxygen content of the neck space and lowers the recontamination risk. Hot- fi lled bottles are fre quent ly overfi lled in order to ensure sterilisation of the neck by the hot prod uct. Another pos si bil i ty for neck ster i li sa tion is to turn

Plastic bottles

Blow-moulded plas tic bottles are an al ter na tive to glass bot tles for orange juice. The most com mon plastic bottles used are high-den si ty polyethylene (HDPE) bottles and polyethylene terephtalate (PET) bottles.

As HDPE has a poor oxygen bar ri er, plain HDPE bottles allow rel a tive ly high ox y gen in- gress and are used for chilled juice of short shelf life (about 3 weeks). The ox y gen bar ri er can be im proved by adding some pol y mers with better bar ri er prop er ties. The most com mon bar ri er lay ers in HDPE bottles for or ange juice are eth- yl ene vi nyl al co hol (EVOH) and polya mide (PA). These can allow ambient stor age for 6 months or long er, de pend ing on the choice and thick ness of the bar ri er lay er. HDPE bottles are fairly opaque, of ten pigmented, and pro duced by the ex tru sion blow-moulding (EBM) process,

PET bottles were in tro duced in the late 1970’s and are now widely used for car bon at ed bever- ages. The application of PET bot tles in the still drink segment is growing stead i ly.

PET bottles are made by stretch blow mould- ing (SBM), starting with a preform. A pre form is an injection-moulded PET tube closed at one end and with the fi nished neck at the open end.

The stretch ing during blowing of the bottle gives high tensile strength and in creased gas bar ri er to provide a lightweight bottle, and thus rel a tive ly low bottle cost. In their nat u ral state PET bot- tles are transparent and col our less, but col oured bottles can be pro duced by add ing ap pro pri ate pigments to the raw PET ma te ri al.

The robustness of PET bottles compared with glass is obvious, but regular PET bottles do not pro vide as good an oxygen barrier as glass. Bar- rier prop er ties for PET bottles in crease with the degree of crys tal lin i ty, which is infl uenced by the conditions during blow mould ing and ma te ri al thickness. Regular PET bottles give a shelf life for orange juice of about three to four months; large volume bottles give a longer pe ri od. Adding a barrier may extend shelf life up to 12 months or more.

There are several methods for barrier ad di tion, such as mix ing the PET polymer with oth er com- pounds, coating the bottle with a bar ri er lay er, or forming several material layers in the pre form. In this case, barrier ad di tion is more com pli cat ed than with ex tru sion blow-mould ed bot tles.

PET (and HDPE for ambient stor age) bot tles are often fi lled by hot fi lling. Aseptic fi lling of PET bottles at ambient temperature requires a signifi cantly larger investment but is increas- ingly gain ing ground as bottlers become more experienced and the aseptic fi ll ing tech nol o gies be come ver i fi ed.

The temperature for hot fi lling of orange juice in PET bottles is 84°C to 88 °C. For the ma te ri al to with stand the high hot fi lling tem per a tures, rel a tive ly thick plastic and special thermal sta- bilisation, “heat setting”, of the bottles during stretch blow moulding are re quired. To with stand the vacuum created when prod uct cools down in the bottle after fi ll ing, PET bot tles for hot fi lling are designed with “vac u um panels” (fl at surfaces on the side of the bottle) or other features that allow bottle contraction.

PET bottles for aseptic fi lling are sterilised prior to fi lling with product. During sterilisation the bot tles are treated with a sterilant such as hy dro gen per ox ide or peroxyacetic acid (PAA) and then rinsed with sterile water. PET bottles

Fig. 9.15 Plastic bottles.

for aseptic fi lling are of lower weight than hot-fi ll bottles and do not need heat setting. This results in lower bottle cost while oxygen permeability is slightly higher. Bottles for aseptic fi lling al low more free dom in their de sign as vac u um pan els or similar features are not need ed.