One of the key concerns at harvest is the period of time from when the grape is removed from the vine (either on the stalk or as a berry) to when it is safe and sound in either a press or fermentation vessel.
During this time the berry is primarily prone to oxidation and microbial spoilage, both of which are exacerbated by higher temperatures. As a result it has become standard practice to add sulphur solution (as Potassium Metabisulphate – PMS) to the harvest bins both before and after the bin is filled with fruit. This method is a good start to mitigating the risk the aforementioned issues, however it still leaves a large portion of the fruit (in the middle of the bin), unprotected. This unprotected pocket will then be broken up and transferred to either the press or fermentation tank, where the process of oxidation is still able to take place.
In order to reduce the threat and effect of oxidation and microbial spoilage at the fruit stage, Naturaliste Vintners designed and built a sulphur dosing unit for our process line. By halving the amount of sulphur added to the harvest bins, and evenly distributing the other half via our dosing system, we are ensuring that every piece of fruit has a uniform and effective addition of sulphur.
Based on our observations this has eliminated any pockets of unprotected fruit from reaching the press or fermentation tanks. Time will tell, but based on our experience with eliminating oxidation and microbial spoilage at other stages of the process, we foresee a greater expression of fruit, lower total sulphur levels in the bottle, and an overall increase in quality.