Effects of cocoon-processing stream and extraction route on Bombyx mori pupae oil fatty-acid composition, quality indices, and thermal transitions

Silkworm pupae represent the major weight by-product of silk production and constitute a promising raw material for oil extraction. In silk processing, pupae can be recovered either from unreelable or defective cocoons (UCP) or after the silk reeling steps (RCP). This study investigated how the extraction method, mechanical pressing versus Soxhlet extraction, and the cocoon-processing stream (RCP/UCP) influence the fatty acid composition, physicochemical quality indices, and thermal behavior of silkworm pupa oil. Soxhlet extraction yielded significantly higher oil recovery, with RCP samples presenting the highest yield (32.87 ± 1.28%) compared with UCP samples (28.70 ± 1.27%). All oils were rich in polyunsaturated fatty acids (>36%), particularly linolenic acid (>28%). Mechanically extracted UCP-oil exhibited the highest peroxide value (5.34 ± 0.77 mEq/kg), whereas UCP-oil obtained via Soxhlet extraction showed the highest acid value (0.33 ± 0.04 mg KOH/g). Color differed significantly among extraction procedures. Melting and crystallization profiles were similar across samples regarding event temperatures, indicating comparable thermal characteristics regardless of extraction method or cocoon-processing stream (RCP/UCP). Overall, the comprehensive characterization of silkworm pupae oil presented here provides valuable insights for its potential integration into food, cosmetic, and pharmaceutical applications, alongside for future valorization strategies in sericulture by-product management.