From reading the side panels on wine kit boxes most people can see that kits contain concentrate, juice and other winemaking staples like acid and sulfite. However, just how these things came together to make your kit is fascinating.

First, manufacturers contract to purchase grapes from growers by specifying conditions at harvest (acid, pH, brix, and color) and organoleptic qualities (flavor and aroma). These specifications tend to be very rigid, for although the grapes may change radically from harvest to harvest, the kits must maintain very high levels of consistency, or consumers will be unable to make repeat purchasing decisions. When the grapes are ripe they are harvested and taken to a winery, where they are sulfited and crushed. At this point white and red grape processing diverges.

White grapes are pressed, and the juice is pumped into a settling tank. Enzymes are added to break down pectins and gums, which would make clearing difficult after fermentation. Bentonite is added to the juice and re-circulated. After several hours the circulation is shut off, and the tank is crash-chilled below freezing. This helps precipitate grape solids, and prevents spoilage.

When the tank is settled, and the juice almost clear, it is roughly filtered, the sulfite is adjusted, and it is either pumped into tanker trucks for shipment to the kit facility, or into a vacuum concentrator (see below).

Red grapes are crushed, sulfited and pumped through a chiller to a maceration tank, where special pectinoglycolytic enzymes are added. These break down the cellulose membrane of the grope skins, extracting color, aroma and flavor. The tank is chilled to near freezing to prevent the must from fermenting. After two to three days the red must is pumped off, pressed and settled much the same way as the whites. The pressed grape skins then undergo secondary processing to extract further skin components (see ‘What’s on the Horizon’)  which can then be added back to the juice.

Vacuum concentrators work like the reverse of a pressure cooker. By lowering the pressure inside the tank, water can be made to boil at less than 120⁰F. At temperatures this low browning and caramelization are prevented, and wafer comes off as vapor, leaving behind concentrated grape juice. Because there are some aromatic compounds that can be carried away in this vapor, there is a fractional distillation apparatus on the concentrator to recover these essences, which are returned to the concentrate after processing.

The juices and concentrates are then shipped to the kit facility (almost all such facilities are in Canada). There they are pumped into nitrogen purged tanks, tested for quality and stability, and held at very low temperatures. This both speeds up the formation of wine diamonds (crystals of potassium bitartrate from the tartaric acid naturally occurring in the wine), and preserves them until they are to be used.

After the Quality Control checks are passed, the juices and concentrates are blended into the formulations that make up the different kits in giant blending tanks. When the formulation is finally adjusted and approved the must is pumped through the pasteurizer. The pasteurizer is a type of heat exchanger that rapidly heats and then cools the must, killing yeast and spoilage organisms without burning or caramelizing the must. From there is goes into the bagfiller which purges the sterile bags with a double flush of nitrogen, and then fills each bag to a very strict weight tolerance.

The bags are then automatically capped and loaded into the kit boxes that come from the box former, after which the packaged additives are placed on top. The boxes are sealed shrink-wrapped and packed on a skid for a Quality Assurance microbiological hold. Depending on the product, this hold can be from three days to more than a week, while the product is examined for signs of bacterial or yeast activity. If it passes, it is then shipped to the warehouse, and from there to dealers, and finally, into the hands of the winemaking customer.