Hot fill jars: is it the end of the line for glass?

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In this feature for Plastics News Europe James Snodgrass looks at PET jars for jam, sauces and other foodstuffs which are designed to lighten the weight of containers while retaining a traditional appearance.

From pasta sauces to jams, glass jars have been the de facto standard packaging for hot fill applications. But as the advantages of plastic jars for producers – lower shipping costs, less loss from breakage – become ever more apparent, will consumers overlook the perceived quality advantages of glass (familiarity, solidity, optical properties) and embrace plastic?

UK-based premium confectionary maker, Fudge Kitchen, certainly hopes so. Its range of sweet sauces, Liquid Fudge, has recently made the transition from glass to plastic packaging.

Fudge Kitchen spokesperson, Kira Harris, is clear about the logistical advantages of plastic hot fill packaging: “Like most transport arrangements, our shipping carton size is set by both physical size and cubic meter parameters. 

“The weight of glass easily pushes the overall cubic load of a case over per-carton shipping constraints resulting in less product being shipped per carton charge. So, the change to plastic packaging does mean that we can now ship more for less.”

But when it comes to consumer perception, the jury is still out. 

Harris continued: “The change-over has been very recent, a matter of weeks. The product is currently in very high demand, [perception of the quality of packaging] is certainly something which we will be keeping a close eye on. However, the feedback which we have received so far has been very complimentary.”

Another driver in the push to bring plastic hot fill packaging into more premium territories is the use of metal lids. By keeping one part of the conventional hot fill jar arrangement (the metal lid that helps distinguish the traditional jar/lid combo), it requires less of a leap of the consumer’s imagination. There is still an air of familiarity.

Among the companies eyeing the market potential for plastic hot fill jars is APPE, the European PET packaging firm now called Plastipak Packaging after its takeover by Plastipak of the US. The company has extended its ThermaLite PET jar range with five new round jars specifically designed for the food market as replacements for glass packaging.

ThermaLite jars can be hot or cold filled at temperatures up to 95°C and then pasteurised at a slightly lower temperature with most methods of pasteurisation.

“This next generation of ThermaLite jars represents a considerable step-change in the ability to use PET jars in the hot-filling and pasteurisation of food products,” said Mike Hanratty, Plastipak’s commercial and business development director. 

The five jars range in size from 212ml to 720ml, all with a 63mm neck opening and all with metal twist-off caps to ensure customer familiarity.

Plastipak claims that fillers can use the shatterproof jars on glass filling lines with little or no modification required, with less downtime and batch spoilage, and with greatly reduced noise levels. 

Weighing in at 85% lighter than glass, the logistical and carbon footprint savings are palpable. Taking the 375ml jar as an example, the company says that with the weight saving over the glass equivalent and the slightly smaller footprint, around 19% more ThermaLite jars can be transported in the logistical chain than glass counterparts. Based on a volume of 10 million jars, this equates to around 73 (or 24%) fewer trucks being used in comparison to glass. 

While Plastipak’s metal closures use a twist-cap, Australian rigid packaging firm Amcor is claiming a world first for hot fill PET containers with metal lug closures. 

Lug caps are traditionally used on jam jars and have a threading system that only requires a half turn to open or close. The A-PEX63 system, was unveiled at the Private Label Manufacturers Association (PLMA) trade show in the US last November.

The technology allows the fitment of metal lug closures to blow-and-trim 24oz hot-fill containers. The company claims that consumers can enjoy the same quality and reassurance of the fresh, tamper-evident “pop” of a metal lug closure on a lightweight, shatter-proof PET jar.

Bunlim Ly, senior marketing manager at Amcor, said: “This is a major development which firmly positions PET hot-fill containers in the food packaging industry. We’ve filled an important need for consumers and brand owners who seek the benefits of PET containers with metal lug closures, delivering the same quality and freshness associated with glass along with significant performance, manufacturing, and sustainability benefits.”

The 700ml stock hot-fill containers are targeted for food applications including jams, jellies, salsas, apple sauce and pesto sauce. As with Plastipak’s ThermaLite hot fill jars, A-PEX63 PET containers have a 63mm neck opening. The containers are hot fillable up to 96°C and available with Amcor’s Powerflex vacuum absorbing base for applications that require enhanced vacuum performance.

The logistical and environmental argument for hot fill PET packaging is obvious. Now that products using these technologies are appearing on store shelves, the market will decide if consumers are ready to accept that glass has had its day.

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