Journal of Advances in Biology & Biotechnology

Defatted ghee residue is a protein-rich dairy by-product that may serve as a substrate for producing bioactive peptides through microbial fermentation. Lactic acid bacteria, particularly Lactiplantibacillus plantarum, possess proteolytic systems capable of hydrolysing proteins into smaller peptides with potential functional properties. However, the time-dependent effects of fermentation on protein hydrolysis and antioxidant activity in defatted ghee residue remain insufficiently characterised. This study evaluated the time-dependent hydrolysis of defatted ghee residue protein during fermentation with Lactiplantibacillus plantarum-025 and examined associated changes in pH and antioxidant capacity. Defatted ghee residue was mixed with distilled water at a 1:10 ratio, adjusted to pH 7, heat-treated, inoculated with 2.5% starter culture, and incubated at 37 ± 1°C for 48 h. Samples were collected at 6 h intervals. Protein hydrolysis was assessed as degree of hydrolysis (DH), while antioxidant capacity was evaluated using DPPH and ABTS radical-scavenging assays. The pH decreased progressively from 7.012±0.006 at 0 h to 3.902±0.027 at 48 h. DH increased from 5.428±0.515% initially to a maximum of 39.750±0.764% at 30 h, before declining to 12.142±1.198% at 48 h. DPPH inhibition varied throughout fermentation, decreasing to 3.619±0.143% at 18 h before increasing and fluctuating at later sampling points. ABTS inhibition increased to 41.133±0.641% at 6 h and subsequently declined and fluctuated. These results indicate that protein hydrolysis and antioxidant responses changed differently over the fermentation period. Prolonged fermentation was not associated with sustained increases in either DH or radical-scavenging activity. Overall, limited fermentation appears preferable for obtaining protein hydrolysates from defatted ghee residue, although the fermentation duration should be selected by considering both hydrolysis and antioxidant responses.