Tensile testing to quantitate the anisotropy and strain hardening of mozzarella cheese

We explored anisotropy of mozzarella cheese: its presence is debated in the literature. Tensile testing proved a good method because the location and mode of failure were clear. Mozzarella cheese cut direct from the block showed no significant anisotropy, though confocal microscopy showed good structure alignment at a microscale. Deliberately elongated mozzarella cheese showed strong anisotropy with tensile strength in the elongation or fibre direction ∼3.5× that perpendicular to the fibres. Temperature of elongation had a marked impact on anisotropy with maximum anisotropy after elongation at 70 °C. We suggest the disagreement on anisotropy in the literature is related to the method of packing the mozzarella cheese into a block after the stretching stage of manufacture. Tensile stress/strain curves in the fibre direction showed marked strain hardening with modulus just before fracture ∼2.1× that of the initial sample, but no strain hardening was found perpendicular to the fibre direction.