Note 1 - Organization, Basis of Presentation, and Summary of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Aug. 26, 2018	Aug. 27, 2017
Product sales	$ 124,668	$ 115,781
Natural Foods [Member]
Product sales	112,051	103,617
Biomaterials [Member]
Product sales	12,617	12,164
Salads [Member] | Natural Foods [Member]
Product sales	49,080	42,048
Aseptic [Member] | Biomaterials [Member]
Product sales	5,766	7,026
Core Vegetables [Member] | Natural Foods [Member]
Product sales	61,750	58,075
Fermentation [Member] | Biomaterials [Member]
Product sales	3,070	2,791
Other [Member] | Natural Foods [Member]
Product sales	1,221	3,494
Development Services [Member] | Biomaterials [Member]
Product sales	$ 3,781	$ 2,347