A comparative study of innovation rennets from Swedish ruminants: calves, kids, and lambs

Abstract: The study aimed to examine Swedish innovation rennets (lamb and kid) and bovine rennets (pepsin and chymosin) in combination with species-specific milk from goat, sheep, and cow. This was accomplished by evaluating the gross composition, casein and whey protein content, casein number of the milk types, as well as rheological properties, such as curd yield, coagulation time, and gel firmness. The milk composition showed that sheep milk had the highest levels for all investigated milk components but the lowest pH, which was 3% lower for cow and goat milk. Comparing the effect of milk type on curd yield using the different rennets, the sheep milk in combination with chymosin resulted in 9% and 35% higher curd yield compared to cow and goat milk, respectively (p=0.001). Pepsin in combination with goat milk resulted in 28% and 30% lower curd yield than for cow and sheep milk, respectively (p=0.001). The lamb rennet with sheep milk showed 12% and 24% higher curd yield than with cow and goat milk, respectively (p=0.001), and the kid rennet with goat milk had a 37% lower curd yield than with cow and sheep milk, respectively (p=0.001). Comparing the effects of the rennets on the curd yield for each milk type, cow milk with chymosin and lamb rennet resulted in a 5% higher curd yield than with kid rennet (p=0.021). Kid rennet with goat milk showed 15% and 29% lower curd yield compared to chymosin and lamb rennet, respectively (p=0.001). The curd yield from sheep milk with lamb rennet was 10% and 17% higher compared to pepsin and kid rennet (p=0.001). The effect of milk type on coagulation time showed that cow milk with chymosin was 50% and 60% longer than in goat and sheep milk (p=0.001). Pepsin with cow milk displayed 44% and 54% higher coagulation time than with goat and sheep milk, respectively (p=0.001). Sheep milk with lamb rennet had 46% and 53% shorter coagulation times than with goat and cow milk, respectively (p=0.001). Within the milk types, the effects of rennets showed that lamb rennet, compared to chymosin, pepsin, and kid rennet, resulted in the longest coagulation time, 9%, 26%, and 54% longer, respectively, in combination with cow milk (p=0.001). Goat milk with lamb rennet showed a 48%, 52%, and 72% longer coagulation time compared to chymosin, pepsin, and kid rennet, respectively (p=0.001). Kid rennet with sheep milk resulted in 47%, 51%, and 61% shorter coagulation time than with pepsin, chymosin, and lamb rennet, respectively (p=0.001). Comparing the effect of milk type on gel firmness showed that chymosin in sheep milk resulted in 84% and 80% higher gel firmness than in cow and goat milk, respectively (p=0.001). Pepsin with sheep milk displayed the highest gel firmness, 83% and 81% higher than for cow and goat milk, respectively (p=0.001). Lamb rennet with sheep milk resulted in 82% higher gel firmness compared to cow and goat milk, respectively (p=0.001). Kid rennet with goat milk showed 49% and 78% lower gel firmness than cow and sheep milk (p=0.001). Within the milk types, the effects of rennets on gel firmness showed that when kid rennet was used in cow milk, gel firmness was 31%, 39%, and 41% higher compared to when pepsin, lamb rennet, and chymosin, respectively, were used (p=0.001). Kid rennet with goat milk showed the lowest gel firmness, 32% lower than for chymosin and pepsin Abstract (p=0.002). Sheep milk with kid rennet resulted in 37% and 41% lower gel firmness compared to chymosin and pepsin rennet (p=0.010). This research indicates that the species-specific innovative rennets from Swedish ruminants can potentially contribute to the optimization of the production of Swedish artisanal cheeses, thereby increasing the added value of the final product.