The potential of beef lungs as a protein ingredient and peptide source : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

Abstract

Beef lungs are an underutilised co-product of the meat industry that could be used as an ingredient to supplement the protein content of cereal foods. Incorporating beef lung into widely consumed food can improve the protein quality of the food chain. Air oven drying was used to convert raw beef lungs to beef lung powder (BLP). Beef lungs were dried at 60˚C for 32 hours and ground into beef lung powder (BLP). BLP was incorporated into the pasta as a model food for delivery of macro and micronutrients. BLP had 87% protein content (dry weight basis) with a rich essential amino acid profile and contained 1 mg/g iron. Fresh semolina pasta was used as a model food, and BLP could be incorporated at up to 20% based on preliminary trials. Incorporation of 10% BLP improved the indispensable amino acid score (IAAS) of the pasta from 0.48 to 0.91, Pasta with 10% BLP showed better textural, colour and cooking characteristics compared to those where BLP was incorporated at 15% and 20% (P <0.05). Incorporation of BLP into the pasta also significantly (P < 0.05) lowered the predicted glycaemic response. Therefore, the inclusion of BLP improved the nutritional value of a starchy food and is a potential ingredient in the development of new food products. Further research was focused on reducing drying time and temperature to lower the cost of production and increase the nutrient content. Raw beef lungs were minced and dried for 23 hours at 50˚C, 11 hours at 70˚C or 6 hours at 100˚C. The resulting BLP powders were analysed for physicochemical and nutritional properties. All of the powders were able to absorb three times their weight in water. The BLP dried at 50°C preserved 40% of the total iron as haem iron, which has a higher bioavailability, but this significantly decreased to 29% when the lungs were dried at 100°C. All the powders dried at 50, 70 and 100 °C were within microbial safety limits for total viable bacterial count, yeast and mould and there was no evidence of coliform bacteria after six months of storage. The higher quality of BLP dried at 50°C was confirmed by low levels of lipid (0.51 MDA mg/Kg sample) and protein (8.6 nmol carbonyl /mg protein) oxidation after six months of storage. The bioaccessibility of the nutrients within BLP dried at different temperatures was assessed using a simulation of human digestion. The dried beef lungs at 50°C had a 96.3% in vitro protein digestibility (IVPD). This was significantly decreased 95.8% with drying at 70°C. In vitro bioaccessibility of copper (Cu), iron (Fe) and sulphur(S) also significantly decreased as drying temperature increased. Bovine lung dried at 50°C could provide highly bioaccessible proteins and minerals for the human body. Local meat processing plants were unable to provide edible beef lungs while meeting stringent export requirements. This prevented conducting any sensory analysis and would make commercialisation of a food supplement from bovine lungs difficult. As a result, the potential for using lungs for the production of bioactive peptides was investigated. The protein in raw beef lungs was digested and the resulting peptides analysed for angiotensin-1 converting enzyme (ACE) inhibitory activity. Kiwifruit extract and the commercial fungal proteases, FP31K and FP60K were used to produce beef lung hydrolysates. Active fractions were purified, and the amino acid sequence of the peptides were analysed by mass spectrometry. The highest ACE inhibitory activity was identified in FP31K enzymatic hydrolysates, and the peptides in this fraction had an IC₅₀ of 24 µg/mL for ACE inhibition. The novel peptide sequence “Val-Ser-Pro-Gly-Met-Pro” was identified as a possible ACE inhibitory peptide. Peptide analysis revealed collagen and elastin as the dominant proteins in beef lung hydrolysates. This study produced economical and nutritious protein powder from beef lungs. This nutritious BLP could be used to supplement starchy food protein and possibly help eliminate world malnutrition, if the regulatory obstacles could be overcome. Meanwhile, the raw beef lungs are a good source for producing ACE inhibitory peptides. If the meat industry could use lungs in pharmaceutical production of ACE inhibitors and other peptides, it would increase profit margins from this underused coproduct.