Voster Muchenje

Natural antioxidants against lipid–protein oxidative deterioration in meat and meat products: A review

Oxidation is a well-known non-microbial cause of quality loss in meat. Oxidative stress occurs due to uneven generation of free radicals reactive oxygen species (ROS) and reactive nitrogen species (RNS) which triggers oxidative and/or nitrosative stress and damage of macromolecules including the lipid and protein fractions. Failure of synthetic antioxidants to combat multiple health risks associated with this stress and maintenance of functional integrity of oxidised meat hitherto remains a challenge to the meat industry. A search for a viable alternative amidst the unexploited novel sources of natural antioxidants stands as a sustainable option for preserving the meat quality. In this paper, the potential use of bioactive compounds in medicinal plants is reviewed as phytoremedy against lipid-protein oxidation. Synergistic antimicrobial potentials of these natural antioxidants are also revealed against oxidative deterioration in meat and meat products and, for enhancing their functional properties.

Nutritional characterization of Moringa ( Moringa oleifera Lam.) leaves

calcium (3.65%), phoshorus (0.3%), magnesium (0.5%), potassium (1.5%), sodium (0.164%), sulphur (0.63%), zinc (13.03 mg/kg), copper (8.25%), manganese (86.8 mg/kg), iron (490 mg/kg) and selenium (363 mg/kg). 17 fatty acids were observed with α-Linolenic acid (44.57%) having the highest value followed by heneicosanoic (14.41%), g-linolenic (0.20%) palmiteic (0.17%) and capric acid (0.07%). Vitamin E had the highest concentration of 77 mg/100 g than beta-carotene, which had 18.5 mg/100 g in the dried leaves. The fiber content was neutral detergent fibre (NDF) (11.4%), acid detergent fibre (ADF) (8.49%), acid detergent lignin (ADL) (1.8%) and (acid detergent cellulose (ADC) (4.01%). The condensed tannins had a value of 3.2%, while total polyphenols were 2.02%. The values of amino acids, fatty acids, minerals and vitamin profiles reflect a desirable nutritional balance.

Meat quality of Nguni, Bonsmara and Aberdeen Angus steers raised on natural pasture in the Eastern Cape, South Africa

The current study compared meat quality of Nguni, Bonsmara and Angus steers raised on natural pasture. Fifteen seven-month-old weaners of each breed were kept at the University of Fort Hare Farm for 12 months till slaughter. Monthly weights of the steers were recorded. Carcasses were electrically stimulated. The m. longissimus thoracis et lumborum was sampled for the measurement of meat colour, pH, drip loss, sarcomere length, myofibrillar fragmentation length and Warner Bratzler (WB) shear force. The Nguni had the highest (P<0.05) average daily gain. Bonsmara and Angus steers had higher (P<0.05) carcass weight and dressing percentage than the Nguni steers. Meat quality characteristics were similar among all the breeds except that Nguni meat was darker (L(∗)) (P<0.05) than meat from the other two breeds. The respective L(∗) values for Nguni, Bonsmara and Angus steers were 36.5, 38.6 and 39.9. There were significant (P<0.05) correlations among some meat quality traits. There were significant (P<0.05) correlations between WB values of meat aged for 2 and 21 days in Nguni and Bonsmara, but not in Angus. Meat quality from Nguni compares favourably with that from established breeds, when raised on natural pasture.

Polyphenolic content and antioxidant properties of Moringa oleifera leaf extracts and enzymatic activity of liver from goats supplemented with Moringa oleifera leaves/sunflower seed cake

The study investigated antioxidant potency of Moringa oleifera leaves in different in vitro systems using standard phytochemical methods. The antioxidative effect on the activities of superoxide dismutase (SOD), catalase (CAT), lipid peroxidation (LPO) and reduced glutathione (GSH) were investigated in goats supplemented with M. oleifera (MOL) or sunflower seed cake (SC). The acetone extract had higher concentrations of total flavonoids (295.01 ± 1.89 QE/g) followed by flavonols (132.74 ± 0.83 QE/g), phenolics (120.33 ± 0.76 TE/g) and then proanthocyanidins (32.59 ± 0.50 CE/g) than the aqueous extract. The reducing power of both solvent extracts showed strong antioxidant activity in a concentration dependent manner. The acetone extract depicted higher percentage inhibition against DPPH, ABTS and nitric oxide radicals which were comparable with reference standard antioxidants (vitamin C and BHT). MOL increased the antioxidant activity of GSH (186%), SOD (97.8%) and catalase (0.177%). Lipid peroxidation was significantly reduced by MOL. The present study suggests that M. oleifera could be a potential source of compounds with strong antioxidant potential.

Relationship between pre-slaughter stress responsiveness and beef quality in three cattle breeds

The relationship between stress responsiveness and beef quality of 40 Nguni, 30 Bonsmara and 30 Angus steers was determined. The L(∗) values, pHu, cooking loss (CL) and Warner-Bratzler shear force (WBSF) were determined. Catecholamine levels were determined from urine samples collected at slaughter. Bonsmara steers had the highest (P<0.05) levels of catecholamines with respective epinephrine, norepinephrine and dopamine concentrations of 10.8, 9.7 and 14.8nmol/mmol. Nguni steers had the lowest (P<0.05) levels of catecholamines, with respective catecholamine concentrations of 5.1, 4.3 and 4.0nmol/mmol. In the Nguni steers, there were significant (P<0.05) correlations between catecholamines and L(∗) and between dopamine and tenderness in meat aged for two days (WBSF2). In the Bonsmara, dopamine was correlated (P<0.05) pHu, WBSF2 and CL. No significant correlations were found in the Angus. Therefore the relationship between stress responsiveness and certain beef quality traits may not be similar in different breeds.

Tick susceptibility and its effects on growth performance and carcass characteristics of Nguni, Bonsmara and Angus steers raised on natural pasture.

The objective of the current study was to compare tick loads, growth and carcass characteristics of dipped and non-dipped Nguni, Bonsmara and Angus steers raised on natural pasture. One hundred 7-month-old castrated weaners were kept at the University of Fort Hare Farm for 12 months. There were 30 weaners each of Angus and Bonsmara, and 40 weaners of the Nguni breed. Half the Bonsmara, Angus and 14 Nguni weaners were dipped every fortnight. The rest were not dipped. Monthly weights and tick counts under the tail, on scrotum, belly, sternum and ears of the steers were recorded. The dipped Nguni steers had lowest (P < 0.05) tick counts, and the non-dipped Angus steers had the highest (P < 0.05) tick counts. There were more ticks (P < 0.05) during the warm wet season than during the cool dry season. Ears had the highest (P < 0.05) tick infestation. Average daily gain (ADG) was similar (P > 0.05) among the three breeds. The non-dipped Bonsmara steers had the heaviest (P < 0.05) carcasses (142 ± 5.4) while the non-dipped Nguni steers had the lightest (P < 0.05) carcasses (111 ± 4.5 kg). The non-dipped Bonsmara had the highest (P < 0.05) eye muscle area (3996 ± 120.8 mm2) while the non-dipped Angus had the smallest (P < 0.05) eye muscle area (3291 ± 210.6 mm2). The non-dipped Bonsmara also had the highest (P < 0.05) dressing percentage (53.8 ± 1.01) while the non-dipped Nguni had the lowest (P < 0.05) dressing percentage (50.3 ± 0.84). The current study has shown that while the non-dipped steers had higher (P < 0.05) tick loads than the dipped steers, their growth and carcass characteristics were similar (P > 0.05). The study has also shown that, despite being a small-framed breed, the Nguni steers had similar (P > 0.05) ADG to the large-framed Bonsmara and Angus steers. Therefore, the Nguni cattle have the potential to produce organic beef. However, a reasonable assessment of organic beef production potential of the Nguni requires an evaluation of its meat quality traits under natural pasture.

Assessing the nutritional status of beef cattle: current practices and future prospects

Accurate determination of nutritional and health status of animals is invaluable in modern animal agriculture. Body weights and body condition scoring are the commonly used methods of assessing nutritional status of animals. This paper discusses drawbacks these methods have and highlights the benefits for using blood metabolites in assessing nutritional status of beef cattle. Blood metabolite levels indicate the extent of metabolism of energy, proteins and other nutrients in animals. Glucose, cholesterol, non-esterified fatty acids, protein, urea, creatinine, albumin, globulin, minerals, liver enzymes and haematology can be used objectively, reliably and routinely to assess the nutritional status of cattle. In Southern Africa, the use of these metabolites is rare due to lack of equipment for blood analysis and the high cost of analyzing the blood parameters. However, use of high value Nguni cattle in Southern Africa requires the use of blood parameters to accurately assess their nutritional status. Several factors, such as physiological status of an animal, breed, nutrition, season and age affect levels of blood metabolites. Combining body weights, body condition scores and blood metabolites increase accuracy of assessing the nutritional state and welfare of beef cattle.

Fatty acid composition and oxidative stability of breast meat from broiler chickens supplemented with Moringa oleifera leaf meal over a period of refrigeration.

Effects of diets supplemented with or without Moringa oleifera leaf meal (MOLM) on fatty acid (FA) composition and oxidative stability of broiler breast meat during refrigerated storage was determined. Dietary treatments (T) were as follows: T1, positive control, 668g/ton Salinomycin and 500g/ton Albac; T2, T3 and T4 contained graded levels of MOLM at 1%, 3% and 5% of dry matter (DM) intake, respectively; and T5, a negative control (0% additives). Oxidative stability was evaluated by thiobarbituric acid reactive substances (TBARS) on day (D) 1-8 of storage at 4°C; and FA analysis was done on samples obtained on D1 and D8. Significant effects on TBARS were noted on day (D) 1, 3, 4 and 7; increased with increasing storage time, and with increase in MOLM supplementation. Highest (P<0.05) C18:0 and C15:0 levels were noted on D1 in T2; C20:0 in T4 on D8; C20:2, C20:3n6 and C22:6n3 in T2; C18:3n6 and P/S ratio in T4 on D1; and n-3 in T3. Thus, despite the high SFA content, additive supplementation of M. oleifera leaf meal up to 5% of the birds DMI improved the FA profile and reduced lipid oxidation in broiler breast meat.

Sensory evaluation and its relationship to physical meat quality attributes of beef from Nguni and Bonsmara steers raised on natural pasture

The current study compared sensory characteristics and their relationships with physical meat characteristics of beef from Nguni and Bonsmara steers. Nguni beef was more (P < 0.05) tender than Bonsmara beef after ageing for 2 and 21 days, and had higher (P < 0.05) intramuscular fat (IMF; 1.12%) than Bonsmara beef (1.07%). Nguni beef had higher (P < 0.05) sensory scores than Bonsmara beef after ageing for 2 days. There were no (P > 0.05) relationships between IMF and sensory characteristics. Aroma intensity, impression on juiciness and tenderness-related scores were affected (P < 0.05) by pH. There were significant (P < 0.05) correlations between most physical meat characteristics and sensory characteristics. Nguni beef had better sensory scores than Bonsmara beef for beef aged for 2 days. While most physical meat characteristics were correlated to sensory scores, all sensory scores were not significantly correlated to IMF.

Atherogenicity index and health-related fatty acids in different stages of lactation from Friesian, Jersey and Friesian × Jersey cross cow milk under a pasture-based dairy system

The objective of the study was to investigate the effect of stage of lactation on the fatty acid profiles of milk from Friesian, Jersey and Friesian×Jersey cows. Linoleic acid in pastures was highest in the second phase which coincided with mid-lactation days (p<0.05). Highest milk moisture content and lowest fat free dry matter content was seen in early lactation (p<0.05). Higher fat content was observed in late lactation than early lactation. Highest butyric, caproic, linoleic, omega-6 and polyunsaturated fatty acids were observed for milk from Friesian cows. Highest conjugated fatty acids, α-linolenic acid, linoleic acid, saturated fatty acids, polyunsaturated fatty acids, omega-6, and omega-3 were observed in early lactation. Atherogenicity index and desaturase activity indices were highest in late lactation. In conclusion, stage of lactation and genotype affected milk health-related fatty acid profiles.