A sweet as idea

The Southland Times - - Catalyst - Will Harvie will.harvie@stuff.co.nz

Re­search has ‘‘de­ter­mined that a plan­ta­tion of maple saplings for use in com­mer­cial pro­duc­tion of maple syrup is a pos­si­ble and a promis­ing en­deav­our in New Zealand’’.

Canada pro­duces 71 per cent of the world’s maple syrup and 91 per cent of that orig­i­nates from the prov­ince of Que­bec. But a clutch of New Zealand aca­demics think this coun­try could have a maple syrup in­dus­try, de­spite a mild cli­mate and no sugar maple forests.

Their pre­lim­i­nary re­search has ‘‘de­ter­mined that a plan­ta­tion of maple saplings for use in com­mer­cial pro­duc­tion of maple syrup is a pos­si­ble and a promis­ing en­deav­our in New Zealand’’, ac­cord­ing to a pre­sen­ta­tion to be given at a chem­i­cal en­gi­neer­ing con­fer­ence in Queen­stown on Oc­to­ber 1.

The most promis­ing places for maple syrup pro­duc­tion are roughly Molesworth Sta­tion and in­land from West­port, both in the South Is­land, ac­cord­ing to their pa­per.

But we’re a long way from pour­ing Kiwi maple m¯ıere over our pan­cakes be­cause the re­search chal­lenges many ac­cepted tru­isms of maple syrup pro­duc­tion.

In North Amer­ica, maple syrup is derived from the sap of maple trees (Acer sac­cha­rum). The sap is mostly colour­less water, with 1 per cent to 3 per cent sugar by weight. Holes are drilled into ma­ture maple trees and nat­u­ral pres­sures within the trees flow the sap into tubes for col­lec­tion.

The sap is then re­duced by heat un­til the sugar con­tent is about 67.5 per cent by weight. It takes about 40 litres of sap to pro­duce 1 litre of syrup. The am­ber colour comes from the heat.

In Que­bec and other syrup re­gions of east­ern Canada and the United States, maple trees are 30-40 years old be­fore they are tapped. These trees typ­i­cally oc­cur in nat­u­ral forests.

Fi­nally, maple trees are un­usual in that sap flows in win­ter. Why is not well un­der­stood, but a freeze-thaw cy­cle is crit­i­cal.

Win­ters in

Que­bec are harsh and overnight tem­per­a­tures are con­sis­tently about mi­nus 10 de­grees Cel­sius. But there are thaws, too.

Over­seas ex­perts had long thought maple sap pro­duc­tion could never oc­cur in New

Zealand be­cause the weather was too mild, wrote lead author Te­naya Driller, a chem­i­cal en­gi­neer­ing PhD stu­dent at the Univer­sity of

Canterbury.

But in 1984, Dave DeGray started plant­ing sugar maples near Nel­son and his tree growth rates are al­most dou­ble those achieved in North Amer­ica, reach­ing tap­pable girth in 20 years. He har­vests some sap.

Driller and her en­gi­neer­ing su­per­vi­sor, Dr Matt Wat­son, are not in­ter­ested in 20-year cy­cles. They adopted a ‘‘plan­ta­tion method’’ that was de­vel­oped at a maple re­search cen­tre at the Univer­sity of Ver­mont.

The key fea­ture is that sap can be ex­tracted from maple trees that are a few years old and a few cen­time­tres in di­am­e­ter at breast height.

The top of the saplings are cut off and a ‘‘sap col­lec­tion de­vice’’ draws out the sap us­ing a par­tial vac­uum. Top­ping the saplings does not kill them. While less sap comes out of each sapling than comes out of each ma­ture tree, the den­sity of a plan­ta­tion makes up the dif­fer­ence.

In a plan­ta­tion, saplings would be 30cm to 100cm apart and there could be 12,000 saplings a hectare. Nat­u­ral forests av­er­age 250 trees a hectare. Mean­while, mod­er­ately cold tem­per­a­tures can pen­e­trate thin saplings and en­cour­age sap pro­duc­tion. It takes more sus­tained and lower cold tem­per­a­tures to pen­e­trate a ma­ture tree. Driller, Wat­son and groups of un­der­grad­u­ates crunched the num­bers and con­cluded the pay­back pe­riod was seven years for a 10ha plan­ta­tion of maple saplings, a vac­uum har­vest­ing sys­tem, plus pro­cess­ing and pack­ag­ing sys­tems. Fi­nally, the re­searchers iden­ti­fied the most likely re­gions for a maple plan­ta­tion and found Molesworth Sta­tion and in­land West­port looked the most promis­ing. These were ‘‘coarse’’ cal­cu­la­tions, Wat­son said.

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