Scientists aim to breed easier-to-crack macadamias with more nut, less shell SatSaturday 23 Professor Bruce Topp's research aims to improve production and profitability for the macadamia industry. ( Share Print text only Cancel If you've ever risked your fingers while hitting a macadamia with a hammer, you'll know that the nuts can be tough to crack, yielding a small but tasty kernel inside. Key points: Macadamias have three layers: the outer husk, the shell and the inner kernel Scientists aim to breed nuts that have tougher husks, thinner shells and larger kernels Some of Australia's brightest horticultural minds are trying to change that by selectively breeding for macadamias with thinner shells, larger kernels and tougher exterior husks to protect the nuts from birds and insects.