Valorization of Artisanal Sour Buttermilk through Nanofiltration and Spray Drying: Recovery of Milk Solids and Application of Permeate as a Coagulant

Artisanal sour buttermilk is generated as domestic waste at the household level during the conservation of milk fat in the form of clarified fat using an artisanal method. Around 15-20 kg of artisanal sour buttermilk is generated during the production of 1 kg clarified fat (ghee). Artisanal sour buttermilk has a huge bulk with low total solids (TSs-4%) and high acidity, and it is usually discarded due to the lack of any suitable technique for its preservation. Henceforth, artisanal sour buttermilk was concentrated up to 19.61% TS employing nanofiltration (NF) at 35±2 ºC and subsequently converted to artisanal sour buttermilk powder using spray drying. This powder exhibited excellent wettability (3 s, instant), flowability (angle of repose- 32.10º), water-binding capacity (4.20 g per g of protein), and emulsion stability (80.15%). Furthermore, NF permeate was used as a natural coagulant to prepare heat- and acid-coagulated milk gel from buffalo milk. Buffalo milk heat- and acid-coagulated gel has been criticized for its hard texture and grainy body. Buffalo milk heat- and acid-coagulated gel prepared using NF permeate exhibited significantly (p<0.05) lower hardness and higher yield over cow milk heat and acid-coagulated gel. The developed process enables conversion of artisanal sour buttermilk (by-product) into an easily digestible, low-lactose and high-protein powder. The permeate is able
to develop soft heat- and acid-coagulated milk gel from buffalo milk. This will also curtail environmental pollution and generate extra income for farmers. Thus, an eco-friendly process was developed to increase environmental sustainability.