Valorization of guava seed oil as a functional ingredient in salad dressing: implications on quality characteristics, rheological behaviour, morphology, oxidative stability and shelf life

Guava seeds constitute 6 to 12% of the fruit weight, which contributes significantly to waste disposal in landfills annually. Guava seed oil (GSO) was extracted and evaluated for its quality attributes and utilized as substitute (10 to 50%) of refined oil in eggless and egg-based salad dressing. The yield of GSO was 10.07%, showing newtonian behaviour with significant amount of phenolic content (91.58 mg GAE/100 g), antioxidant capacity (52.91%) and total carotenoids (20.75 µg/g). FTIR spectra at 1742 1/cm confirm the presence of linoleic acid. Results showed that upto 20% level of GSO substitution in salad dressing results in superior organoleptic scores in comparison to higher levels. GSO substitution significantly (p ≤ 0.05) influenced the ash, acidity, pH, free fatty acid, peroxide vale of the salad dressing. Both salad dressings substituted with 20% GSO displayed significant (p ≤ 0.05) increases in total phenols (5.85%–8.23%) and total carotenoids (58.45%–61.12%), as result of which antioxidant activity also increased (18.17%–29.48%). Optical microscopy and particle size distribution confirmed that GSO substitution in salad dressing lowered the mean particle size and increased specific surface area, thus indicating increased oxidative stability of salad dressing. GSO substitution enhanced the viscosity, as salad dressing demonstrated pseudoplastic flow during shear rate. Storage studies (3 months) revealed GSO substituted exhibited better quality characteristics, antioxidant activity and oxidative stability in comparison to control. Results confirmed that GSO has a potential for substitution in salad dressing as functional components which enhanced the quality and storage stability of the salad dressing.