Recent advances in activated water systems for the postharvest management of quality and safety of fresh fruits and vegetables.

Over the last three decades, decontamination management of fresh fruits and vegetables (FFVs) in the packhouses and along the supply chains has been heavily dependent on chemical-based wash. This has resulted in the emergence of resistant foodborne pathogens and often the deposition of disinfectant byproducts on FFVs, rendering them unacceptable to consumers. The management of foodborne pathogens, microbial contaminants, and quality of FFVs are a major concern for the horticultural industries and public health. Activated water systems (AWS), such as electrolyzed water, plasma-activated water, and micro-nano bubbles, have gained significant attention from researchers over the last decade due to their nonthermal and nontoxic mode of action for microbial inactivation and preservation of FFVs quality. The aim of this review is to provide a comprehensive summary of recent progress on the application of AWS and their effects on quality attributes and microbial safety of FFVs. An overview of the different types of AWS and their properties is provided. Furthermore, the review highlights the chemistry behind generation of reactive species and the impact of AWS on the quality attributes of FFVs and on the inactivation/reduction of spoilage and pathogenic microbes (in vivo or in vitro). The mechanisms of action of microorganism inactivation are discussed. Finally, this work highlights challenges and limitations for commercialization and safety and regulation issues of AWS. The synergistic prospect on combining AWS for maximum microorganism inactivation effectiveness is also considered. AWS offers a potential alternative as nonchemical interventions to maintain quality attributes, inactivate spoilage and pathogenic microorganisms, and extend the shelf-life for FFVs.

Impact of electrolyzed water as pre-treatments on drying properties and total colour difference of fresh-cut 'Tommy Atkins' mangoes.

Mango fruits are a rich source of nutrients, however, due to their perishability and seasonality, minimal processing and drying offer the potential ensure a shelf stable and safe product. The use of sodium metabisulphite (SMB) as pre-treatment in the dried fruit industry has been widely adopted, but sulphite residue remains a health public concern. Therefore, this study investigated the effects of alkaline and acidic electrolyzed water (AIEW and AEW, mg/mL) as alternative pre-treatments to SMB (1% w/w) for 'Tommy Atkins' mango slices prior to hot air drying at 60 °C. Fresh-cut and untreated samples were used as a control. During the drying process the weight of the slices were monitored every 60 min for 10 h, which was used to calculate moisture ratio (MR), drying rate (DR), and the experimental data of the samples were subjected to eight thin layer models. Colour parameters (L*, a*, and b*) were measured, and use to determine colour intensity (C*), hue angle (h°), and total colour difference (TCD) before and after drying. Based on measured weight, continuous decline in MR was recorded for all dried mango slices over the drying time irrespective on treatment. Out of the eight applied thin layer models Henderson & Pabis and Logarithmic were the best appropriate models describing and predicting the drying behavior of 'Tommy Atkins' mangoes (R2 = 0.94, RMSE ≥ 0.0006). Samples treated with AEW treated samples had lowest L*, h°, and TCD values (p < 0.05). No significant different were found in h° values amongst all pre-treated and dried samples (p > 0.05), but these samples were significantly different from dried untreated (control) and fresh samples (p < 0.05). Pre-treatments maintained the visual quality of dried 'Tommy Atkins' mango slices; SMB > AIEW > AEW > untreated (control). This study provided science-based evidence for the application of acidic and alkaline electrolyzed water as an alternative pre-treatment to sodium metabisulphite for the drying of 'Tommy Atkins' mango.

Phenolic composition and total antioxidant capacity of South African frozen concentrated orange juice as affected by varietal, seasonal and regional differences.

BACKGROUND: There is epidemiological evidence that fruits and vegetables promote general health due to their phenolic composition. The phenolic composition of three commercially important citrus varieties ('Mandarin', 'Navel' orange and 'Valencia' orange), used for frozen concentrated orange juice (FCOJ) production in South Africa, were evaluated based on variety, production season and geographical region (Western Cape (WC) and Eastern Cape (EC)). RESULTS: FCOJ from the WC had significantly (P < 0.05) lower titratable acidity (TA) and higher total soluble solids (TSS):TA ratio compared to FCOJ produced in the EC. The 'Navel' FCOJ, irrespective of season and region, had the highest (P < 0.05) phenolic content (sum of quantified compounds, TP). Regional effects were clear for the 'Mandarin' variety, the EC 'Mandarin' FCOJ had the highest TP and WC 'Mandarin' had the lowest. Seasonal differences were less evident. Variation that could be ascribed to regional differences were also found for individual phenolic compounds. CONCLUSION: Robust data regarding the phenolic profile of FCOJ produced in South Africa, suitable for inclusion in food composition databases, were collected. © 2018 Society of Chemical Industry.

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

The concentrations of 16 metals were assessed in snoek(Thyrsites atun; n=20) and yellowtail (Seriola lalandi; n=37) sampled from the West and South-East coasts of South Africa. Variability was observed at both small (Al, Cr, Hg, Pb, Mn and Cu) and large (As and Cu) spatial scales while inter-specific examination revealed diverse metal concentrations in snoek (Higher levels: Cr, Mn, Co, Hg and Pb) and yellowtail (higher levels: Fe and Cu). Zn, As and Hg were positively correlated with yellowtail size with no such correlations in snoek. Mean concentrations of As (0.61mg·kg-1; 0.98mg·kg-1), Cd (0.008mg·kg-1; 0.004mg·kg-1), Hg (0.27mg·kg-1; 0.16mg·kg-1) and Pb (0.009mg·kg-1; 0.005mg·kg-1) for snoek and yellowtail respectively were within regulatory guidelines. However, 10% (n=2) of snoek exceeded Hg maximum allowable limit, suggesting caution and further investigation. Overall, two meals (150g) per week of snoek or larger yellowtail (12-15kg) can be safe for human (adult) consumption.

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.

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.

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.

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.

The effects of gender, size and life-cycle stage on the chemical composition of smoothhound shark (Mustelus mustelus) meat.

BACKGROUND: Knowledge on the chemical composition of foods, and on the variation in such components as influenced by endogenous factors, is required for nutritional labelling, dietetic planning and food processing. This study examined the effects of endogenous factors (gender, size and life-cycle stage) on the chemical components (proximate, amino acid, fatty acid, mineral and mercury contents) of smoothhound shark (Mustelus mustelus) meat. RESULTS: Levels of moisture, protein, lipids, ash, amino acids and most minerals were not affected (P > 0.05) by the gender, size or life-cycle stages of the sharks. The fatty acid content was higher in females than in males, as well as in non-pregnant females compared to pregnant females. Certain fatty acids decreased in quantity in medium-sized sharks (prior to maturity). Pregnant females had higher aluminium (Al) and copper (Cu) levels than non-pregnant females and mercury (Hg) levels were highest in large male sharks. CONCLUSION: This study has, for the first time, established that endogenous factors have minimal influence on the chemical composition of M. mustelus meat, demonstrating the feasibility of describing an average composition for this species. Additionally, new insights have been obtained on potential safety concerns (mercury) associated with consumption of the meat that require further investigation.

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.

Kinetic optimisation of the reversed phase liquid chromatographic separation of rooibos tea (Aspalathus linearis) phenolics on conventional high performance liquid chromatographic instrumentation.

Rooibos tea, produced from the endemic South African shrub Aspalathus linearis, has various health-promoting benefits which are attributed to its phenolic composition. Generating reliable, quantitative data on these phenolic constituents is the first step towards documenting the protective effects associated with rooibos tea consumption. Reversed phase liquid chromatographic (RP-LC) methods currently employed in the quantitative analysis of rooibos are, however, hampered by limited resolution and/or excessive analysis times. In order to overcome these limitations, a systematic approach towards optimising the RP-LC separation of the 15 principal rooibos tea phenolics on a 1.8 µm phase using conventional HPLC instrumentation was adopted. Kinetic plots were used to obtain the optimal configuration for the separation of the target analytes within reasonable analysis times. Simultaneous optimisation of temperature and gradient conditions provided complete separation of these rooibos phenolics on a 1.8 µm C18 phase within 37 min. The optimised HPLC-DAD method was validated and successfully applied in the quantitative analysis of aqueous infusions of unfermented and fermented rooibos. Major phenolic constituents of fermented rooibos were found to be a phenylpropanoid phenylpyruvic acid glucoside (PPAG), the dihydrochalcone C-glycoside aspalathin, the flavones isoorientin and orientin, and a flavonol O-diglycoside tentatively identified as quercetin-3-O-robinobioside. Content values for PPAG, ferulic acid and quercetin-3-O-robinobioside in rooibos are reported here for the first time. Mass spectrometric (MS) and tandem MS detection were used to tentatively identify 13 additional phenolic compounds in rooibos infusions, including a new luteolin-6-C-pentoside-8-C-hexoside and a novel C-8-hexosyl derivative of aspalathin reported here for the first time.