“primary process”, in relation to any product produced in the course of pastoral, agricultural or other farming operations, means the first process to which such product is subjected by an agricultural co–operative in order to render such product marketable or to convert such product into a marketable commodity, and includes any further process carried on by such co–operative which is so connected with the said first process that such first process and such further process or processes may be regarded as one process and to be necessary to convert such product into a marketable commodity;