ALBERT

Description: The cold water palinurid Jasus lalandii ('West Coast rock lobster') is a commercially important crustacean in South Africa and Namibia and inhabits the Benguela Current Eastern Boundary System. This habitat is characterised by strong upwelling events in summer and algal blooms with their subsequent decay in autumn. Upwelling can lead to acute hypercapnia whereas the algal decay is associated with acute hypercapnic hypoxia. Both types of hypercapnic events could become more frequent and severe in the future due to ongoing climate change. The aim of the present study was, however, to study the capability and mechanisms of response in J. lalandii to hypercapnia exclusively. Accordingly, the following research questions were formulated: 1) To what extent is haemocyanin oxygen-binding affinity of adult J. lalandii pH-sensitive? 2) Can adult male J. lalandii respond swiftly to drastic changes in pH? 3) What physiological mechanisms facilitate a potential response to a drastically declining pH, i.e. acute hypercapnia? These questions were answered by analysing 1) the pH sensitivity of the haemocyanin's oxygen binding properties and 2) in vivo changes in the acid-base balance of adult J. lalandii during acute exposure to hypercapnia (pH 7.4). Results showed the following: 1) Haemocyanin displays a strong Bohr shift (whole haemolymph: delta logP50/delta pH = -1.17; dialysed haemolymph: delta logP50/delta pH = -0.84) in response to lowering of pH. 2) Acute hypercapnia leads to a decline in extracellular pH within the initial 1.5 h of exposure. 3) Thereafter, active compensation becomes apparent as the bicarbonate levels start to increase, with complete compensation reached after 5 h of exposure (+ 2.3 mmol/l; + 48%). 3) This bicarbonate increase is reversed when returning lobsters to normocapnia (pH 7.9). 4) Levels of molecular modulators of haemocyanin oxygen affinity (Ca2 +, Mg2 + and l-lactate) do not change during acute exposure to hypercapnia. Our results show the capability of adult J. lalandii to rapidly and fully compensate the experienced extracellular acidosis, protecting oxygen carrying capacity of haemocyanin and ensuring an outward gradient of CO2. The West Coast rock lobster is therefore well equipped for its habitat where these hypercapnic events are known to occur frequently.

Description: Few studies exist reporting on long-term exposure of crustaceans to hypercapnia. We exposed juvenile South African rock lobsters, Jasus lalandii, to hypercapnic conditions of pH 7.3 for 28 weeks and subsequently analysed changes in the extracellular fluid (haemolymph). Results revealed, for the first time, adjustments in the haemolymph of a palinurid crustacean during chronic hypercapnic exposure: 1) acid-base balance was adjusted and sustained by increased bicarbonate and 2) quantity and oxygen binding properties of haemocyanin changed. Compared with lobsters kept under normocapnic conditions (pH 8.0), during prolonged hypercapnia, juvenile lobsters increased bicarbonate buffering of haemolymph. This is necessary to provide optimum pH conditions for oxygen binding of haemocyanin and functioning of respiration in the presence of a strong Bohr Effect. Furthermore, modification of the intrinsic structure of the haemocyanin molecule, and not the presence of molecular modulators, seems to improve oxygen affinity under conditions of elevated pCO2.

Description: : Insects have the ability to convert biowaste into valuable functional compounds, such as proteins, fat and chitin. Currently, unlike with conventional commodities, there are few fractionation methods to isolate these compounds for diversification of use. Enzymatic hydrolysis is a possible method to fractionate Hermetia illucens larvae, into protein, fat and chitin. This method is a particularly attractive due to the milder process conditions required compared to chemical methods, the relative ease to control the reaction and minimal formation of unpalatable and toxic by-products. A central composite design was used to help identify the optimum hydrolysis conditions for fractionation. At these conditions the fat recovery was ?~81%; substantially more than previous attempts and the fatty acid profile stayed unchanged from the original larvae material. The protein solubility was ~57%, with a degree of hydrolysis of ~22%, and was on par with previous studies. The amino acid profile of the soluble proteins differed from the original larvae material with a slight decrease in the ratio of essential to total amino acids. The insoluble proteins were accounted for with the chitin. A washing-and-sieving step, as means to recover the insoluble proteins from the chitin is envisaged. Also, the spray drying of the protein hydrolysate produced and its functional properties allows for future investigation. This technology allows for higher margins to be made, both environmentally as well as financially, compared to the use of the ‘intact’ biomass.

Description: Noted for its unique herbaceous flavour which is imbued from a diet of indigenous fragrant plants, Karoo lamb is marketed as one of South Africa’s finest meat products and enjoys Protected Geographical Indication (PGI) status in South Africa and the European Union. Its distinct quality is imparted through natural grazing of the sheep on the Karoo veld that has a significant influence on the sensory and chemical profile of the meat. Descriptive sensory analysis, fatty acid analysis, solid-phase microextraction, isotope ratio mass spectrometry, portable near-infrared reflectance spectroscopy and proton transfer reaction-mass spectrometry proved to be very successful analytical tools for the authentication of regionally unique lamb meat, distinguishing Karoo from Non-Karoo lamb. Characteristic volatiles, specifically terpenes, present in both the Karoo bushes and the Karoo lamb meat and fat were detected. The dominant terpenes were tentatively identified as α-pinene, β-pinene, limonene and trans-caryophyllene, and they were particularly prominent in the fat tissue. Within the Karoo, regional differences were apparent as Hantam Karoo lamb had the highest ratings for herbaceous aroma and flavour and contained the greatest concentration of terpenes. Herbaceous aroma and flavour attributes associated with a diet rich in fragrant Karoo plants were verified with stable isotope ratio analysis. The results confirm that Karoo bushes are responsible for the distinct aroma and flavour of Karoo lamb, thereby providing vital evidence for its certification and to justify the protection of its indicator status.

Description: The use of the black soldier fly (BSF: Hermetia illucens) as a means of upstreaming waste has enjoyed increasing research the past few years. One of the uses of the resultant larvae is as animal feed, with particular success achieved when fed to mono-gastric animals. Most of the research has been on the use of BSF as feed in poultry and fish species. In poultry, larvae were produced on abattoir waste, kitchen waste or faecal matter (human and animal manure). The insects were grown until harvest as larvae, pre-pupae or pupae. The post-harvest processing included freezing, drying and/or milling. Where the poultry were fed Iso-nitrogenous/Iso-energetic diets containing various proportions of BSF, no differences in production performance or carcass yields (breast-, thigh-yields) were found. As pertaining to meat quality, no differences for initial pH or ultimate pH of the meat were noted. Differences for breast colour measurements were found; larvae fed chicken breast meat was generally lighter and redder whilst results on the breasts’ water binding capacity was inconclusive. For sensory attributes, no differences were observed except for juiciness and sustained juiciness. Sometimes a metallic flavour was noted, particularly on larvae fed on abattoir wastes. Manipulating the larvae’s diet as a strategy to change the chemical composition of the poultry has focused on attempts to change the fatty acid profiles and yielded mixed results; irrespective of the fatty acid profile, the fat of BSF larvae contains large amounts of lauric acid; known to have profound antiviral and antibacterial activity.

Description: Near-infrared (NIR) spectroscopy, combined with multivariate data analysis techniques, was used to rapidly differentiate between South African game species, irrespective of the treatment (fresh or previously frozen) or the muscle type. These individual classes (fresh; previously frozen; muscle type) were also determined per species, using hierarchical modelling. Spectra were collected with a portable handheld spectrophotometer in the 908–1676-nm range. With partial least squares discriminant analysis models, we could differentiate between the species with accuracies ranging from 89.8%–93.2%. It was also possible to distinguish between fresh and previously frozen meat (90%–100% accuracy). In addition, it was possible to distinguish between ostrich muscles (100%), as well as the forequarters and hindquarters of the zebra (90.3%) and springbok (97.9%) muscles. The results confirm NIR spectroscopy’s potential as a rapid and non-destructive method for species identification, fresh and previously frozen meat differentiation, and muscle type determination.

Description: The chemical characteristics (proximate composition, amino acids, and fatty acids) and sensory quality of the longissimus lumborum (LL) muscle of 45 farmed male fallow deer were investigated. The animals were divided into three separate groups (n = 15 per treatment): pasture-fed (P), pasture-fed and supplemented with barley (B), and pasture-fed and supplemented with barley and lysine (BL). Differences were observed in LL moisture and the intramuscular fat contents, the latter being almost two-fold greater in the meat of B and BL groups compared to P. The concentrations of histidine, leucine, alanine, glutamic acid and glycine in the raw meat were higher in the BL group compared to the P group. Higher contents of n–3 polyunsaturated fatty acids (PUFAs), and consequently lower n–3 ratios, were found in the P group, compared to the BL group. The grilled meat samples from the P group scored higher than the other groups for grassy flavour, and lower for liver flavour.

Description: Although fallow deer are abundant in South Africa, these cervids remain undervalued as a domestic protein source and little information exists on their meat quality. This study aimed to evaluate the proximate and mineral compositions of the meat from wild fallow deer (n = 6 male, n = 6 female) harvested in South Africa, as affected by sex and muscle. Proximate analyses were conducted on six muscles (longissimus thoracis et lumborum [LTL], biceps femoris [BF], semimembranosus [SM], semitendinosus [ST], infraspinatus [IS], supraspinatus [SS]), whereas mineral analyses were conducted on the LTL and BF. The proximate composition of the muscles ranged from 73.3–76.2% moisture, 20.4–23.1% protein, 2.2–3.2% fat, and 1.1–1.5% ash. Proximate composition was significantly (p ≤ 0.05) influenced by muscle, but not by sex. The primary essential macro- and micro-minerals determined in the LTL and BF were potassium, phosphorus, sodium, and magnesium, as well as iron, zinc, and copper, with more variation in concentrations occurring with muscle than with sex. Minerals in the muscles contributing most notably to human recommended dietary requirements were potassium, iron, copper, and zinc. These findings indicate that wild fallow deer meat is a nutritious food source and should enhance utilisation of such products.

Description: The effect of production systems on the sensory quality characteristics of Dorper lambs was investigated. Sixty lambs (ewes, rams, castrates) were allocated into two production groups (feedlot or free-range) at weaning with equal numbers of each sex represented in each group. The lambs were fed for five (slaughter group 1) or six (slaughter group 2) weeks. Feedlot lambs were fed a commercial pelleted diet while free-range lambs utilized natural shrub pastures. Samples of the Longissimus thoracis muscle were used for sensory evaluation. Feedlot lambs produced meat that was juicier and more tender than meat from free-range lambs. Initial juiciness was also higher in the meat from the feedlot lambs. No aroma or flavour differences were observed. The meat from the free-range ram lambs (slaughter group 1) was the least tender, whereas the lamb flavour was also compromised in the free-range ram lambs. Free-range meat may not necessarily be distinguished from feedlot meat as far as aroma and flavour are concerned.