Raw material nuts may be quenched using an extremely low temperature liquefied gas to produce cracks in the raw material nuts. The cracked raw material nuts may then be crumbled along the cracks to separate the nuts into small nut fragments. After returning the temperature of the nuts to the ambient temperature, additional cracks can be further produced in the nut fragments by quenching the nut fragments. Smaller nut fragments can then be obtained by crumbling along the cracks. Small nut fragments in desired sizes may be obtained by repeating the process of cracking and crumbling as many times as desired. The astringent skin of the nuts may also be peeled off while the small nut fragments are produced.