Note 9 - Business Segment Reporting - Operations by Business Segment (Details) - USD ($)	3 Months Ended
	Aug. 26, 2018		Aug. 27, 2017
Net sales	$ 124,668,000		$ 115,781,000
Gross profit	16,337,000		18,802,000
Net income (loss) from continuing operations	190,000		2,355,000
Depreciation and amortization	3,145,000		2,954,000
Dividend income	413,000		413,000
Interest income	46,000		31,000
Interest expense, net (1)	758,000	[1]	404,000
Income tax expense (benefit)	64,000		1,310,000
International [Member]
Net sales	23,828,000		21,673,000
Natural Foods [Member]
Net sales	112,051,000		103,617,000
Gross profit	13,370,000		15,280,000
Net income (loss) from continuing operations	1,768,000		3,821,000
Depreciation and amortization	2,095,000		2,052,000
Dividend income	413,000		413,000
Interest income	31,000		11,000
Interest expense, net (1)	587,000	[1]
Income tax expense (benefit)	663,000		1,096,000
Natural Foods [Member] | International [Member]
Net sales	20,112,000		18,174,000
Biomaterials [Member]
Net sales	12,617,000		12,164,000
Gross profit	2,967,000		3,522,000
Net income (loss) from continuing operations	(547,000)		(155,000)
Depreciation and amortization	976,000		865,000
Dividend income
Interest income
Interest expense, net (1)		[1]
Income tax expense (benefit)	(182,000)		(27,000)
Biomaterials [Member] | International [Member]
Net sales	3,716,000		3,499,000
Other Segments [Member]
Net sales
Gross profit
Net income (loss) from continuing operations	(1,031,000)		(1,311,000)
Depreciation and amortization	74,000		37,000
Dividend income
Interest income	15,000		20,000
Interest expense, net (1)	171,000	[1]	404,000
Income tax expense (benefit)	(417,000)		241,000
Other Segments [Member] | International [Member]
Net sales

[1] Beginning in first quarter of fiscal 2019, the Company began allocating interest expense to its reportable segments in information provided to its CODM to enhance visibility into how financing activities impact the discrete financial results.