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Answers to Questions about Glass for Food & Drink

By: Berlin Packaging Specialist
Date: January 26, 2020

Glass for Food & Drink

Why do some products only require pasteurization while others need sterilization? The pasteurization process — which destroys microflora — must be immediately followed by rapid cooling of the product and it is suitable for acidic products (such as fruit juices, tomato sauce, beer, etc.).

The sterilization process is necessary for food products with low acidity (e.g., fish, meat, vegetables, etc.), which are more susceptible to bacterial infection that may create pathogens. The increase in temperature from 95°C for pasteurization to 125°C for sterilization enables the bacteria to be destroyed and, with the creation of a vacuum inside the container, the contents to be preserved. When the button at the center of the lid is depressed, it shows that the container is properly sealed and the vacuum inside the container has been maintained. When the button is raised, this shows that the vacuum in the container has been lost and the safe preservation of the contents can no longer be guaranteed.

Why is glass the most hygienic material for packaging purposes? Because glass is completely neutral to its content: it neither releases anything nor absorbs anything from the product (taste, odor, or aroma). It has a high chemical resistance and is waterproof and gas-proof. It can be easily sterilized, has antistatic properties, and does not pollute the environment. It is completely indifferent to climate variations.

Why is there sometimes a numeric code on glass containers? EC Law 178/2002 specifies traceability requirements for food products and the need to be able to retrace every single step of the food supply chain. EC regulation 2023/2006 governs GMP (Good Manufacturing Process) rules. This is why many glass factories — in order to comply with the above rules — print numeric codes on their bottles which indicate the production day, time, or other production details even once the container has been filled and separated from the production identification code attached to the pallet. Generally, this printing is carried out with special inks which are visible only under UV light or by using laser technology.

The use of traditional indelible ink is very rare. Filler companies — which are directly obliged to make their products totally traceable — print their reference codes on the glass or the lid using inks which are visible to the naked eye.

Why isn’t shatterproof glass used for food containers? This is possible because it is a secondary process, but shatterproof glass is not generally used for large scale production of containers because it is unnecessary for the type of use and would be much more expensive because of the procedure.

What is the "plastic grid" used for? The plastic grid, usually made of food-safe plastic, is used in jars to keep products entirely submerged in their preservation liquid (oil or other liquids).

What is the difference between cosmetic glass and glass for food products? The difference lies essentially in the use of specific raw materials in the mixture, which tends to favor products that enhance “shine” (by using barium for example) rather than the mechanical features. In cosmetic packaging, nickel alloy cast iron is used for the molds in order to increase the glossy finish of glass containers.

Is there a special process for making beer bottles? Bottles that are especially designed for classic or craft beers (with fermentation in the bottle) are not manufactured using particular technical features except for the resistance to pressure, since — like the champagne method — they must resist up to 6 bar. They are generally made in amber or dark green glass for better protection from UV rays.

What is the difference between an ordinary glass bottle and a bottle used for sparkling wine? There are some technical differences: in sparkling wine bottles the shape of the bottle is different (e.g., bottles with sharp edges are not suitable), the weight of the glass needs to be of sufficient thickness to withstand the internal pressure, and there is a picure (punt) or a heavier, stronger base. Moreover, they also need to have a uniform distribution of the glass.

How is the size of a cork for a wine bottle determined? The size of a cork (width) is always calculated taking into account the type of wine (still or sparkling) and the internal caliber of the container at a depth of around 40 – 50 mm (about 18.5 mm on average). For still wines, this diameter +6 mm is used for natural corks or +4 mm for technical cork stoppers such as the double-disc cork. Sparkling wines always have double-disc corks, so 4 mm are added.

For spumantes (Italian sparkling wine), a single kind of cork is used that is ø 30.5 mm (the cork starts off larger in order to maintain the pressure). The cork height is 40 mm due to problems in remaining air-tight and because it is the minimum size possible for the cutting and processing of cork. This can vary from 40 to 54 mm for various reasons but mainly for marketing purposes. A cork of 48 mm in height is always used for spumante.

Sometimes in wine shops there are very big champagne bottles. Are they as functional as ordinary bottles, or do they only have an aesthetic purpose? They are certainly as functional as the ordinary bottles, but they are subject to very strict quality controls because of their size and their sparkling content. They are generally used in sizes from Magnums to Methuselahs, and more rarely Salmanazars and Nebuchadnezzars and their resistance is tested up to 16 bar. The last four are used very rarely because of dangers related to champagne pressure in such high quantities. They have been used for sparkling wines, as in the case of the 27 liter “primat” (which corresponds to 36 ordinary bottles) to celebrate Moser’s Hour record in Mexico City.

What is the "picure" or "punt" used for? The picure or punt was originally used to collect wine sediment. Today, it is used to guarantee better resistance to pressure for sparkling wine or fizzy drinks or for aesthetic reasons linked to tradition.

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