Three good sorts

It’s been a tough vintage in many New Zealand regions this year. Three cyclones created wet and sometimes humid condition forcing many producers to harvest grapes before they reached optimum ripeness. Wet weather also encouraged the development of rot.

Grape selection can be a life-saver in such conditions. Three different, widely-used sorting methods can dramatically increase wine quality.

Hand-picking grapes (Photo: Bob Campbell MW)

Selective grape-picking

I watched grape pickers thoughtfully reject around 50% of their pinot noir grapes in the 2009 vintage.

When the chips are down hand-harvesting can make a real difference. It relies on a diligent grape-picking crew and careful instruction. I watched grape pickers thoughtfully reject around 50% of their pinot noir grapes in the 2009 vintage. That may be an accountant’s nightmare but the wine was terrific.

Producers who wish to machine harvest sometimes send in a picking crew ahead of the machines to remove as many rotten bunches as possible.

Hand-sorting grapes at Destiny Bay (Photo: Bob Campbell MW)

The sorting table

Hand-sorting grapes inside the winery is an expensive but effective process. I witnessed a team of sorters working hard for Waiheke producer, Destiny Bay, and that was after a careful selection when the bunches were removed from the vine. Hand-sorting can be done before the wines go through a destemmer, or when the berries emerge from the destemmer, sometimes both.

It’s more critical to sort red grapes than white because the presence of botrytis, and its associated enzyme, laccase, can cause browning in red wine. Kumeu River winemaker, Michael Brajkovich MW, recalls a Burgundian winemaker saying “we use the sorting table for reds but don’t bother sorting whites.” One advantage of sorting inside rather than in the field is the constant artificial light which makes imperfections easier to spot.

Machine sorting grapes (Photo: Pellenc Australia)

Machine sorting

They are not cheap (NZD $100,000-plus) but modern optical sorting machines are increasingly common in medium and large wineries. They use high-speed cameras and image-processing software to scan grapes on a fast-moving conveyor. Defective grapes are removed by a shot of compressed air. I saw a machine in action at Hawke’s Bay winery, Paritua.

Before the machine sorting process begins the producer picks and hand sorts a couple of boxes of grapes, using them to program the machine’s rejection rate.

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