A total of 15 walnut (Juglans regia L.) samples from 15 cultivars from different geographical areas (Villaviciosa, Colunga, Ribadesella, Llanes, Nava, Peñamellera and Sariego) from Asturias, Spain were studied. Samples of virgin walnut oil were obtained from dehusked ground walnuts by extraction at a pressure of 160 kg cm -2 and temperature below 40°C for 3 min. The oil obtained by pressure was filtered for analysis. Fatty acid, sterol and tocopherol compositions as determined by capillary column gas chromatography (GC) and triacylglycerols composition as determined by high performance liquid chromatography (HPLC) are reported. The overall composition (percentages of husk, oil and moisture) was also determined. The higher percentages of fatty acids, as determined by capillary GC, corresponded to palmitic (6.11 ± 0.06-7.49 ± 0.04%), oleic (11.70 ± 1.10-18.90 ± 1.19%), linoleic (59.81 ± 1.03-64.77 ± 1.25%) and linolenic (11.11 ± 0.05-15.65 ± 1.09%). c-Tocopherol was the major component of the total tocopherols in the sample under study (289.01 ± 6.02-676.52 ± 5.98 mg kg -1 oil). b-Sitosterol was the major sterol found (78.61 ± 1.45-86.50 ± 1.35%) followed by D 5 -avenasterol (5.54 ± 0.92-13.81 ± 1.06%). The main triacylglycerides were LLL (24.67 ± 1.31-29.

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Background Lactose from cheese whey permeate (WP) was efficiently isomerised to lactulose using egg shell, a food‐grade catalyst, and the subsequent transgalactosylation reaction of this mixture with β‐galactosidase from Bacillus circulans gave rise to a wide array of prebiotic carbohydrates derived from lactose and lactulose. Results Lactulose obtained by efficient isomerisation of WP (16.1% by weight with respect to the initial amount of lactose) showed great resistance to the hydrolytic action of β‐galactosidase from B. circulans, which preferentially hydrolysed lactose, acting as a galactosyl donor and acceptor. Lactulose had capacity as an acceptor, leading to the formation of lactulose‐derived oligosaccharides. The enzymatic synthesis was optimised by studying reaction conditions such as pH, temperature, time, enzyme concentration and carbohydrate concentration. The maximum formation of galactooligosaccharides with degrees of polymerisation from 2 to 4 was achieved after 5 h of reaction at pH 6.5 and 50 °C with 300 g kg−1 carbohydrates and 3 U mL−1 β‐galactosidase. Conclusion These findings indicate that the transgalactosylation of isomerised WP with β‐galactosidase from B. circulans could be a new and efficient method to obtain a mixture with 50% of potentially prebiotic carbohydrates composed of lactulose, and galactooligosaccharides derived from lactose and lactulose.