Gunnar O. Sigge

Heavy metals in marine fish meat and consumer health: a review

The numerous health benefits provided by fish consumption may be compromised by the presence of toxic metals and metalloids such as lead, cadmium, arsenic and mercury, which can have harmful effects on the human body if consumed in toxic quantities. The monitoring of metal concentrations in fish meat is therefore important to ensure compliance with food safety regulations and consequent consumer protection. The toxicity of these metals may be dependent on their chemical forms, which requires metal speciation processes for direct measurement of toxic metal species or the identification of prediction models in order to determine toxic metal forms from measured total metal concentrations. This review addresses various shortcomings in current knowledge and research on the accumulation of metal contaminants in commercially consumed marine fish globally and particularly in South Africa, affecting both the fishing industry as well as fish consumers.

Variation in phenolic content and antioxidant activity of fermented rooibos herbal tea infusions: role of production season and quality grade.

Data are required to calculate the dietary exposure to rooibos herbal tea flavonoids and phenolic acids. Representative content values for the principal phenolic compounds and total antioxidant capacity of fermented rooibos infusion, taking into account variation caused by production seasons (2009, 2010, and 2011) and quality grades (A, B, C, and D), were determined for samples (n = 114) from different geographical areas and producers. The major phenolic constituents were isoorientin and orientin (>10 mg/L), with quercetin-3-O-robinobioside, phenylpyruvic acid glucoside, and aspalathin present at >5 mg/L. Isovitexin, vitexin, and hyperoside were present at <3 mg/L. Rutin, ferulic acid, and isoquercitrin were present at <2 mg/L. Nothofagin was present at <1 mg/L. Only traces of luteolin-7-O-glucoside and the aglycones quercetin, luteolin, and chrysoeriol were present. Substantial variation was observed in the individual content values of the phenolic compounds and total antioxidant capacity within production seasons and quality grades.

Mercury accumulation in Yellowfin tuna (Thunnus albacares) with regards to muscle type, muscle position and fish size.

The concentrations and relationships between individual mercury species and total mercury were investigated in different muscle parts and sizes of Yellowfin tuna (Thunnus albacares). Fourteen Yellowfin tuna caught in the South Atlantic off the coast of South Africa had an average total Hg (tHg) concentration of 0.77 mg/kg wet weight. No differences were detected (p > 0.05) in tHg, MethylHg (MeHg) or inorganic Hg (iHg) accumulation among the four white muscle portions across the carcass, but both tHg and iHg were found in higher concentrations (p < 0.001) in dark muscle than white muscle. Positive linear correlations with fish weight were found for both tHg (r = 0.79, p < 0.001) and MeHg (r = 0.75, p < 0.001) concentrations. A prediction model was formulated to calculate toxic MeHg concentrations from measured tHg concentrations and fish weight (cMeHg = 0.073 + 1.365 · tHg-0.008 · w). As sampling sites and subsampling methods could affect toxicity measurements, we provide recommendations for sampling guidelines.

EFFECT OF TEMPERATURE AND RELATIVE HUMIDITY ON THE DRYING RATES AND DRYING TIMES OF GREEN BELL PEPPERS (CAPSICUM ANNUUM L)

ABSTRACT Green bell pepper dices were dehydrated at different dry bulb air temperatures (55°, 60°, 65°, 70° and 75°C) and relative humidities (15, 20, 25, 30, 35 and 40%). The effects of temperature and relative humidity (RH) on the drying rates and drying period of diced green bell peppers were determined. Drying rate curves were characterized by a short induction (heating) phase followed by a falling rate period. Near constant rate drying was observed only at 55°C at 15% RH and at 65°C (15% RH). Drying rates generally increased with increasing temperatures and decreasing RH. The effect of temperature on the drying rates became less pronounced with increasing RH Drying rate maxima at 70°C and RH of 15, 20 25 and 40% exceeded those at 75°C, possibly due to case-hardening.

Heavy metal accumulation and toxicity in smoothhound (Mustelus mustelus) shark from Langebaan Lagoon, South Africa.

Together with several health benefits, fish meat could introduce toxins to consumers in the form of heavy metal contaminants. High levels of mercury (Hg), especially, are frequently detected in certain predatory fish species. Mustelus mustelus fillets were analysed for 16 metals and three individual Hg species (inorganic Hg, ehtylmercury, methylmercury) with inductively coupled plasma mass spectrometry (ICP-MS) and HPLC-ICP-MS respectively. Eleven of the 30 sharks had total Hg levels above the maximum allowable limit with toxic methylmercury found as the dominant mercury species with a strong correlation (r = 0.97; p < 0.001) to total mercury concentrations. Limited correlations between metals and shark size parameters were observed; therefore metal accumulation in M. mustelus is mostly independent of size/age. Average values for arsenic (28.31 ± 18.79 mg/kg) exceed regulatory maximum limits and Hg (0.96 ± 0.69 mg/kg) is close to the maximum limit with all other metals well below maximum limits.

Muscle-specific colour stability of blesbok (Damaliscus pygargus phillipsi) meat

The increasing demand for meat from alternative species, such as blesbok (Damaliscus pygargus phillipsi), gives rise to the need for characterizing the quality attributes of fresh meat from these species. While muscle-specific colour stability has been extensively studied in conventional livestock, limited information is available on this phenomenon in game meat. Therefore, the objective of this study was to examine the colour stability of three major blesbok muscles, infraspinatus (IS), longissimus thoracis et lumborum (LTL) and biceps femoris (BF). Instrumental colour, surface myoglobin redox forms, and biochemical attributes influencing colour stability were measured on 2.5-cm steaks from blesbok IS, LTL, and BF during refrigerated storage under aerobic conditions for eight days. IS steaks consistently demonstrated higher (P≤0.05) redness, colour stability, and chroma than the LTL and BF steaks. These findings suggested that blesbok IS muscle is more colour-stable than its LTL and BF counterparts. The game industry may employ muscle-specific strategies to improve marketability of fresh blesbok meat.

Quantitative analysis of DL-lactic acid and acetic acid in Kefir using near infrared reflectance spectroscopy.

To be able to monitor in real time the concentrations of DL-lactic acid and acetic acid present in Kefir, a self-carbonated fermented milk product, near infrared (NIR) calibration models were constructed based on NIR spectra of 174 samples. Enzymatic tests and gas liquid chromatography were the reference methods used for DL-lactic acid and acetic acid, respectively. The fit of the models and their prediction power were evaluated using segmented cross-validation and an external validation set. The models obtained for DL-lactic acid were found to be acceptable for both cross-validation (R2=0.90, SECV=0.110 g 100 mL−1 and RPD=3.16) and external validation (r2=0.87, SEP=0.156 g 100 mL−1 and RPD=2.57). In contrast, the models for acetic acid were found to be unacceptable. The results obtained for both cross-validation (R2=0.80, SECV=0.013g 100 mL−1 and RPD=2.21) and external validation (r2=0.44; SEP=0.017 g 100 mL−1 and RPD=1.17) suggested this model requires further development. The application of principal component analysis (PCA) to the entire sample set showed Kefir prepared with laboratory Kefir grains (LG), traditional Kefir grains (TG) and mass cultured Kefir grains (MG) resulted in similar PCA score values in spite of the Kefir grains not having the same origin. PCA was also able to differentiate between fermented and “milky body-like” samples. The findings of this study could serve the dairy industry in monitoring more efficiently the acidity in terms of DL-lactic acid of fermented dairy products.

Postharvest losses of cabbages from retail to consumer and the socio-economic and environmental impacts

Purpose – The purpose of this paper is to quantify the incidence of postharvest losses of cabbage at retail purchase and during consumer simulated storage. Design/methodology/approach – Physical losses, changes in quality and nutritional value were determined using produce from three different retail outlets in South Africa. Economic losses and the environment impact associated with postharvest losses of cabbage were estimated. Findings – After seven days in storage, high incidence of postharvest losses occurred, ranging from 12 per cent under cold storage to 46 per cent under ambient conditions. These losses were equivalent to over R10 million (∼US

Insects as human food; from farm to fork: Insects as human food

1 million) per annum, while the equivalent wasted fresh water was estimated to be sufficient to meet the needs of over 217,000 per annum. Research limitations/implications – Study was only conducted in one town and to get the real impact of the losses the research should cover a wider coverage area. Originality/value – Cabbage is one of the most widely consume...

Metal concentrations and toxicity in South African snoek (Thyrsites atun) and yellowtail (Seriola lalandi)

Over the course of the last few years, the consumption of insects, known as entomophagy, has sparked increasing interest amongst scientists and environmentalists as a potential solution to the inevitable global food security and sustainability issues humans will be facing in the coming years. Despite the fact that insects have been an integral part of over 2 billion peoples diet worldwide, the concept of eating insects is still new to Western culture. As a result, there are many unknowns regarding insects as a food source, and this has led to a number of studies and investigations being done in recent years to create more knowledge and awareness around this new concept in the food industry. This review discusses some of the key topics and new developments published over recent years, such as the nutritional benefits, food safety concerns, functional properties, potential product concepts and the current ideas and attitudes towards insects as a food source in Western culture.