A food wash reference fluid delivery apparatus comprising: a portable reference fluid reservoir comprising an inlet and an outlet and configured to store a reference fluid that includes a predetermined concentration of an analyte; a pump fluidly coupled to the outlet of the portable reference fluid reservoir and configured to pump the reference fluid from the outlet of the portable reference fluid reservoir; a sensor connector configured to fluidly couple with a sensor positioned along a fluid flow path of a food wash system; a sensor fluid line configured to provide the reference fluid from the pump to the sensor connector; an inlet fluid line configured to provide the reference fluid from the pump to the inlet of the portable reference fluid reservoir; one or more valves (1902A, 1902B) configured to adjustably control a fluid flow rate of the reference fluid through at least one of the sensor fluid line or the inlet fluid line; characterised in that it further comprises: a battery, wherein the pump is configured to be solely powered by the battery; and a protective pump case configured to support the weight of the portable reference fluid reservoir with the reference fluid contained in the portable reference fluid reservoir, wherein: the pump and the battery are positioned within the protective pump case; the protective pump case is connected to or disposed adjacent to a lower end of the portable reference fluid reservoir; and the protective pump case comprises an access door configured to allow access to the pump through an opening of the protective pump case. a portable reference fluid reservoir comprising an inlet and an outlet and configured to store a reference fluid that includes a predetermined concentration of an analyte; a pump fluidly coupled to the outlet of the portable reference fluid reservoir and configured to pump the reference fluid from the outlet of the portable reference fluid reservoir; a sensor connector configured to fluidly couple with a sensor positioned along a fluid flow path of a food wash system; a sensor fluid line configured to provide the reference fluid from the pump to the sensor connector; an inlet fluid line configured to provide the reference fluid from the pump to the inlet of the portable reference fluid reservoir; one or more valves (1902A, 1902B) configured to adjustably control a fluid flow rate of the reference fluid through at least one of the sensor fluid line or the inlet fluid line; characterised in that it further comprises: a battery, wherein the pump is configured to be solely powered by the battery; and a protective pump case configured to support the weight of the portable reference fluid reservoir with the reference fluid contained in the portable reference fluid reservoir, wherein: the pump and the battery are positioned within the protective pump case; the protective pump case is connected to or disposed adjacent to a lower end of the portable reference fluid reservoir; and the protective pump case comprises an access door configured to allow access to the pump through an opening of the protective pump case. a battery, wherein the pump is configured to be solely powered by the battery; and a protective pump case configured to support the weight of the portable reference fluid reservoir with the reference fluid contained in the portable reference fluid reservoir, wherein: the pump and the battery are positioned within the protective pump case; the protective pump case is connected to or disposed adjacent to a lower end of the portable reference fluid reservoir; and the protective pump case comprises an access door configured to allow access to the pump through an opening of the protective pump case. the pump and the battery are positioned within the protective pump case; the protective pump case is connected to or disposed adjacent to a lower end of the portable reference fluid reservoir; and the protective pump case comprises an access door configured to allow access to the pump through an opening of the protective pump case.