(Reuters) - At South Africa's Rostberg and Co., green bottles filled with a ruby liquid clink as they march along a conveyor belt, destined for wine-lovers from Paris to Shanghai. But if a trend toward bulk shipping continues, the music of the Rostberg bottling plant may be about to stop. Set in lush vineyards in Stellenbosch, one of South Africa's most famous wine communities, Rostberg has been operating below capacity for the past two years due to a shift to shipping wine in 24,000-litre polypropylene "flexitanks".

The trend has spread through other "New World" wine-producing countries like Chile, Argentina, Australia and New Zealand, which all have distant markets and, in the latter two cases at least, relatively strong currencies that are forcing them to cut costs to stay competitive.