Impact of pink rock salt and Lactobacillus spp. on physico-chemical, microbiological properties, phenolic profile and sugar level of apple peel

Abstract

Apple peel is a waste from industrial juice processing that contains many phenolic compounds and it remains underutilised due to low storability. In the present study, an effort on improving storability of apple peel with minimum detrimental loss in the nutrients was made. The apple peel was stored for 7 days with 2.5% pink rock salt (T1PRS), Lactobacillus spp. inoculum (T2Lac) and concoction of both (T3PRSLac) at 30 °C and further evaluated for physico-chemical and microbiological characteristics. The diverse phenolic profile of apple peel showed dominant presence of rutin, chlorogenic acid, myricetin, quercetin and kaempferol. The rutin content notably increased from 40.6 to 765.7 mg kg−1 for apple peel stored with T2Lac. Apple peel with T1PRS, T2Lac and T3PRSLac revealed augmented phenolic content. The peel with T1PRS, T2Lac and T3PRSLac demonstrated decrease in all sugars. The peel stored with T2Lac showed the highest increase in titratable acidity and viable cell counts of Lactobacillus spp. The colour parameters also varied significantly and an improvement in antioxidant activity with different treatments was noticed. The peel stored with T2Lac revealed approximately nine-fold increase in total flavonoid content. The total phenolic content increased from 2808 mg GAE kg−1 to 3830 mg GAE kg−1 as a result storage of peel with T2Lac. The improved storability of apple peel will further help in valorisation.