Technical Yearbook 2023

AUGUST

spoilage yeast Brettanomyces can migrate into the wood’s pores as dead or living cells. Pseudomycelia formed by this yeast can also favour its penetration into the wood. Micro biofilms can also form on the wood surface. Sanitation methods that can remove these micro-organisms at depth are consequently preferred. High-pressure ultrasound (HPU) is a sophisticated sanitation technology. After the barrel is filled with water at 60°C, a sonotrobe is inserted through the bunghole, and a contact time of five to 13 minutes at a pressure of 6 900 kPa is applied. During this period, the bitartrate removal and destruction of the micro organisms happen simultaneously. Another advantage of the technique is energy saving because the HPU treatment can be followed by rinsing with filtered water, which can be reused up to 100 times. Due to the less invasive nature of the treatment, the lifespan of barrels can be extended up to two to three years. It does not only remove all bitartrate deposits but also kills 100% of all viable Brettanomyces cells on the surface and up to a depth of 4 mm. Depending on the barrel size and wine contact, it will reduce the viable population to a tolerable concentration up to 6 mm. It also does not change the wood structure up to a depth of 8 mm. Hot water sanitation of barrels Although ultrasonic sanitation is preferred for Brettanomyces control, other microbial infections are easily controlled by hot water treatment. Hot water at approximately 80°C for a minimum of 20 minutes Steam vapour kills Brettanomyces and lactic acid bacteria like Lactobacillus and Pediococcus . This treatment saves water, extends the life of barrels and is a more natural way of treatment. It kills all bacteria, and barrels are dry after the treatment, ready to be used again. However, total deactivation of yeast up to a depth of 8 mm remains a problem, and the Australian Wine Research Institute (AWRI) recommends high-pressure steam and/or hot water treatment at 85°C as an effective treatment. However, it is challenging to maintain a hot water temperature of 85°C.  References https://www.wineland.co.za/the-ultrasonic-sanitation-of barrels/ effectively removes acetic acid bacteria. High-pressure steam vapour sanitation

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The ultrasonic sanitation of barrels By Charl Theron The purchase cost of grapes and barrels are the two major expenses of cellars. Although it is said that wine is made in the vineyard, that belief can be spoiled by micro-organisms like Brettanomyces residing in expensive barrels. The proper sanitation of barrels is essential to prevent this. Ultrasound and ultrasonics The frequency of sound waves is measured in hertz (Hz), as indicated in figure 1. Ultrasound is defined as sound waves with a frequency above 20 kHz, which is also the approximate limit of sound audible by young, healthy humans. Ultrasound is applied by different ultrasonic devices in various fields by converting electrical energy into ultrasound waves. The food and beverage industries, which utilise micro-organisms in their production processes, are exposed to potential microbial spoilage. Traditional methods like heat, biocides or filtration may have regulatory restrictions or sensory impacts on the treated products. High-power ultrasound (HPU) is a technology that has been evaluated in different food and beverage products, but only to a limited extent in the wine industry. Ultrasonic sanitation of barrels Ultrasonics is the latest technology for the sanitation of barrels. Bitartrate crystals precipitated on the inside surface are effectively removed. However, micro-organisms like the

Animals and chemistry

Medical and destructive Diagnostic

Low base notes

FIGURE 1. The spectrum of different sound waves.

20 kHz

2 MHz

200 MHz

20 Hz

Infrasound

Acoustic

Ultrasound

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TECHNICAL YEARBOOK 2023