Scenario 3 – Reducing Salt Intake

A report by the Scientific Advisory Committee on Nutrition (SACN) concluded that the evidence of a link between salt and high blood pressure was substantial and they recommended that work should be undertaken to reduce salt intake in the UK. As part of your work for a food manufacturer, you have been tasked with establishing salt levels that do not perceptually differ from the current salt levels in one of the popular snack foods that you produce. You design an experiment that utilises the Method of Limits to determine how sensitive individuals are to changes in salt in your snack. You use the snack that's currently on the market as a standard stimulus, and you have developed a number of comparison snacks with more or less salt in them. Participants have to decide if the comparison stimulus has a higher salt content (H), the same salt content (S), or is lower in salt content (L) compared to the standard. Here is a typical set of results from one of the tasters:

Salt content (grams per kg)	A	D	A	D	A	D	A	D	A	D
56.0						H
54.0		H				H		H
52.0		H				H		H		H
50.0		H		H	H	H		H		H
48.0		H	H	H	S	H	H	H		H
46.0	H	S	S	H	S	H	S	H	H	S
44.0	S	S	S	S	S	H	S	S	S	S
42.0	S	S	S	S	S	S	S	S	S	S
40.0	S	S	S	S	S	S	S	S	S	S
38.0	S	L	S	S	S	S	S	S	S	S
36.0	S		S	L	S	L	S	L	S	S
34.0	L		L		S		L		L	L
32.0	L		L		L		L		L
30.0	L		L		L		L		L
28.0	L				L				L
26.0	L				L				L

A/D: Ascending/Descending series

Estimate the interval of uncertainty for this taster.

Calculate the difference threshold.

Calculate the PSE.

Based on your calculations, what would you recommend as a reasonable reduced salt content that would be perceptually unnoticeable to the customer? Justify your answer.