From wheat grain to finished flour

Wheat arrives at the mill from farms, the Grain Marketing Board (GMB), or import shipments from Russia, Canada, and Australia. The grain is weighed, sampled for quality - including moisture content, protein level, and foreign matter - and stored in large silos.

National Foods' Bulawayo plant has an 11,000-tonne wheat silo providing 36 to 40 days of milling stock. Temperature and humidity are carefully controlled to prevent spoilage and insect infestation.

Before milling, the wheat passes through a series of cleaning machines that remove stones, metal fragments, dust, weed seeds, broken grains, and other foreign material. Equipment includes separators, destoners, aspirators, scourers, and magnetic separators.

This stage is critical for both food safety and flour quality. Even small contaminants can damage the milling equipment or compromise the finished flour.

Clean wheat is mixed with precise amounts of water and left to rest for 12 to 24 hours. This process, called tempering or conditioning, toughens the outer bran layers so they separate cleanly during milling, while softening the inner endosperm so it breaks down into fine flour particles.

The exact moisture level and resting time depend on the wheat variety. Hard wheat requires more water and a longer rest than soft wheat.

The conditioned wheat enters the roller mill, the heart of the flour mill. Modern roller mills use pairs of corrugated steel cylinders rotating at different speeds. The first 'break' rolls crack open the grain, separating the endosperm from the bran and germ.

The material then passes through a series of reduction rolls that progressively grind the endosperm into finer and finer particles. Between each set of rolls, the material is sifted through plansifters - large vibrating sieve boxes with multiple layers of fabric or mesh. This repeated cycle of grinding and sifting is called the gradual reduction process. A modern flour mill may have 15 to 20 stages.

The extraction rate determines the type of flour produced. White flour typically has a 72% to 76% extraction rate. High-extraction or wholemeal flour uses 85% to 100% of the grain.

Under Zimbabwe's Food and Food Standards Regulations of 2016 (SI 120 of 2016), wheat flour must be fortified with multiple micronutrients. Since June 2017, all industrially milled wheat flour in Zimbabwe must contain: Vitamin A, Vitamins B1, B2, B3, B6, and B12, folic acid, iron, and zinc.

A pre-mixed fortificant powder is added to the flour stream at a precise, controlled rate using specialised dosing equipment. Quality control tests are performed throughout each shift to verify fortification levels. This mandatory programme aims to address micronutrient deficiencies, particularly in women and children under five.

The finished flour is stored in large bins, then packed into bags. Retail packs (typically 1 kg, 2 kg, 5 kg, and 10 kg) are filled, sealed, and labelled with nutritional information, fortification declarations, and brand identity.

Bulk flour for industrial bakeries and food manufacturers is packed in 25 kg or 50 kg bags, or transported in tanker trucks. From the mill, flour is distributed throughout Zimbabwe and into regional Southern African markets.