Factors affecting heat induced changes in khoa : A Review

Abstract

Khoa also known as mava, khava or palghoa, is a partially dehydrated milk product, prepared by continuous heating and manual stirring-cum-scraping until it reaches a semi solid (doughy) consistency. Various physico-chemical changes occur in milk during khoa preparation. Heating results in denaturation of milk protein forming coagulated mass. Browning reactions viz. maillard (caused due to the interaction of lactose with protein) and caramelisation browning is induced in milk during khoa preparation.  Elevated temperature also results in formation of heat degraded products. Microstructure of khoa as revealed by scanning electron microscopy consisted of protein agglomerated protein mass and void spaces in matrices. The shelf-life of khoa is two to four days under ambient conditions and three weeks under refrigerated conditions. Khoa is very liable to oxidative, microbial and physico-chemical deterioration during storage. The shelf-life can be enhanced by using vegetable parchment paper wrappers, plastic (polyethylene) film bags/pouches, laminated (preferably aluminium coated) pouches, tin plates, or cans in pack sizes. Several additives such as antioxidants (BHT and BHA), bacteriocins (nisin) and preservatives (sorbic acid and potassium sorbate and their salts) are also used to enhance shelf life of khoa.