Detection of clenbuterol in beef meat,liver and kidney by mid‐infrared spectroscopy (FT‐Mid IR) and multivariate analysis

Mid‐infrared spectroscopy (FT‐Mid IR) coupled with multivariate analysis was used to predict clenbuterol in beef meat, liver and kidney. A SIMCA model was also developed to discriminate between pure (beef meat, liver and kidney) and spiked with clenbuterol samples (beef meat‐clenbuterol, liver‐clenbuterol and kidney‐clenbuterol). The best models to predict clenbuterol concentrations were obtained using the partial least squares algorithm (PLS) with a R² > 0.9 and SEC and standard error of prediction <0.296 and 0.324, respectively. The SIMCA model used to discriminate pure and spiked with clenbuterol samples showed 100% correct classification rate. Methods detection limit was 2 μg kg^?1. FT‐Mid IR coupled with chemometrics could be a simple and rapid screening tool for monitoring clenbuterol in beef meat, liver and kidney implicated in food poisoning. This method could be use for screening purposes.     

DEVELOPMENT OF A CHEMILUMINESCENT ELISA FOR DETERMINING OKADAIC ACID IN SHELLFISH

ABSTRACT

An indirect competitive enzyme‐linked immunosorbent assay with chemiluminescent (CL‐ELISA) detection for okadaic acid (OA) in mussel muscle was developed. A hybridoma cell line secreting monoclonal antibody against OA was established after immunization of BALB/c mice with artificially synthesized OA‐bovine serum albumin as antigen. Luminol solution was used as the substrate for horseradish peroxidase. The detection limit was 0.175 ng/g. The range of average fortified recovery was 91.8–102.6% when OA was spiked in mussel muscle at levels of 50, 160 and 800 µg/kg. The standard curve for OA showed good linearity over the concentration range of 0.08125–20 ng/mL. The cross‐reactivity with dinophysistoxin1 and saxitoxin was 51.82 and 0%, respectively. In a residue study, the results obtained by CL‐ELISA correlated well within those obtained using the commercial ABRAXIS kit (ABRAXIS, Warminster, PA). The developed method is therefore suitable for detecting the residues of OA in shellfish.

PRACTICAL APPLICATIONS

Diarrhetic shellfish poisoning is a gastrointestinal syndrome that occurs in humans following the consumption of bivalve mollusks contaminated with OA with the main symptoms of diarrhea, nausea, vomiting and abdominal pain. OA widely exists at marine products and it is very important to develop a technique to monitor this toxin. In this study, a sensitive competitive indirect enzyme‐linked immunosorbent assay with chemiluminescence for determination of OA in mussel soft tissues was investigated. Chemiluminescent ELISA (CL‐ELISA) is a good alternative method for screening samples. This technique has the potential to improve the sensitivity of the immunoassays by at least two to three orders of magnitude compared with conventional colorimetric detection.     

Fermentation dynamics of Lactobacillus helveticus H9 revealed by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry

Lactobacillus (L.) helveticus H9 is a probiotic strain that can produce antihypertensive peptides during milk fermentation. This study analysed the dynamics of skim milk fermentation by L. helveticus H9 by ultra‐performance liquid chromatography coupled to quadrupole time‐of‐flight mass spectrometry (UPLC/Q‐TOF MS). A total of 1992 metabolites were detected from all of the fermented samples in the LC‐MS analysis by multivariate statistical analysis. Metabolites with variable importance in projection (VIP) values ≥2 were considered differentially abundant among samples and were responsible for the unique taste and nutritional and functional qualities of fermented milk. Valine, threonine, l ‐methionine, tyrosine, asparagine and leucine were the predominant amino acids produced during fermentation, and their quantities changed remarkably during the fermentation process. Citric acid and uric acid were the major, and only detectable, organic acids. Some intermediate metabolites, such as N‐acryloylglycine and nicotinamide‐N‐oxide, were also detected. Moreover, certain oligopeptides such as Val‐Leu, Lys‐Gly, Ala‐Glu, Asp‐Ser, Leu‐Pro and Val‐Phe‐Ala were not detected until the middle and late fermentation periods. This study demonstrated dynamic metabolic changes, providing a strong foundation for deciphering the physiological and biochemical mechanisms of the fermentation process.     

Development of a green two‐dimensional HPLC‐DAD/ESI‐MS method for the determination of anthocyanins from Prunus cerasifera var. atropurpurea leaf and improvement of their stability in energy drinks

This study aimed to develop a green two‐dimensional HPLC‐DAD/ESI‐MS method for analysing anthocyanins from Prunus cerasifera var. atropurpurea leaf and improve their stability in energy drinks by the addition of phenolic acids. Ethanol and tartaric acid solutions were used as mobile phases for one‐dimensional HPLC‐DAD for quantitative analysis of anthocyanins, and the primary anthocyanins were identified as cyanidin‐3‐O‐galactoside, cyanidin‐3‐O‐glucoside and cyanidin‐3‐O‐rutinoside using two‐dimensional HPLC‐MS. Method validation showed that the developed method was accurate, stable and reliable for the analysis of P. cerasifera anthocyanins. The effects of gallic, ferulic and caffeic acid on the stability of cyanidin‐3‐O‐galactoside, cyanidin‐3‐O‐glucoside, cyanidin‐3‐O‐rutinoside and total anthocyanins from P. cerasifera leaf in energy drinks were evaluated, and the degradation of P. cerasifera anthocyanins ideally followed a first‐order model (R² > 0.98). Gallic acid showed stronger protective effects on P. cerasifera anthocyanins in energy drinks, and adding/increasing ferulic and caffeic acids accelerated the degradation reactions.     

Effect of high‐pressure processing on immunoreactivity,microbial and physicochemical properties of hazelnut milk

This study investigated the effects of high‐pressure processing (HPP) and thermal processing (TP) on the overall quality attributes of hazelnut milk. HPP achieved the same microbial safety as TP, and the pH, °Brix and sugar contents were maintained at the levels of fresh hazelnut milk. Although HPP caused colour changes, the ?E was smaller than that of the TP sample. Increasing pressure significantly decreased the immunoreactivity of the hazelnut milk by 70%, while simultaneously reducing the levels of essential and non‐essential amino acids and chemical score (CS) and the essential amino acid index (EAAI) values. However, neither HPP nor TP significantly affected the fatty acid composition of hazelnut milk. HPP retained higher total phenolic and flavonoid levels of the hazelnut milk, with a better antioxidant capacity than TP samples. Thus, the HPP maintained microbial safety during cold storage, and physicochemical properties of the treated hazelnut milk were not significantly different from those of the fresh hazelnut milk.     

Influence of temperature,calcium and sucrose concentration on viscoelastic properties of Prosopis chilensis seed gum and nopal mucilage dispersions

Viscoelastic properties of two nontraditional hydrocolloid dispersions were evaluated. Prosopis chilensis seed gum was evaluated based on temperature (5–80 °C) and added CaCl₂ (0.07%), whereas nopal mucilage was evaluated based on temperature (5–80 °C) and sucrose concentration (0–20%). Viscoelasticity was tested by the small strain oscillatory shear test; storage modulus (G′), loss modulus (G″) and tan δ were reported. Prosopis chilensis and nopal dispersions behaved as weak gels (G’ > G’’) regardless of experimental condition. Raising temperature from 20 to 80 °C significantly increased G’. The gel structure was strengthened by adding CaCl₂ and G’ increased at 40 °C. The sucrose effect depended on concentration and temperature; at low sucrose concentrations, G’ modulus increased regardless of temperature level, but at high concentrations, it decreased at temperatures >40 °C. In conclusion, nopal and Prosopis chilensis dispersions show weak gel structure regardless of experimental condition. G′ increases as temperature increases, and these dispersions could be suitable for food applications requiring heat tolerance.     

Isolation and identification of two major acylated anthocyanins from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) by UPLC‐QTOF‐MS/MS and NMR

In recent years, researches on the isolation and preparation of monomeric anthocyanins have intensified because of the requirements of quantitative and structure–bioactivity relationship analyses. However, simple and effective methods about the scale of monomeric anthocyanins from the natural purple sweet potato powder are rarely reported. In this study, high molecular weight acylated monomeric anthocyanins were isolated from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) via the combination of column chromatography and semi‐preparative HPLC technology and identified mainly by ultra‐high‐performance liquid chromatography quadrupole time‐of‐flight tandem mass spectrometry/mass spectrometry (UPLC‐QTOF‐MS/MS) and ¹H and ¹³C nuclear magnetic resonance (NMR). Two major acylated anthocyanins were unambiguously determined as peonidin 3‐O‐(6‐O‐(E)‐caffeoyl‐(2‐O‐(6‐O‐p‐hydroxybenzoyl)‐β‐D‐glucopyranosyl)‐β‐D‐glucopyranoside)‐5‐O‐(β‐D‐glucopyranoside) and peonidin 3‐O‐(6‐O‐(E)‐caffeoyl‐(2‐O‐(6‐O‐(E)‐feruloyl)‐β‐D‐ glucopyranosyl)‐β‐D‐glucopyranoside)‐5‐O‐(β‐D‐glucopyranoside). The results of this study may help promote the purification of high molecular weight acylated anthocyanins from purple sweet potato as well as from other plant materials in nature.     

Enzymatic extraction of fucoxanthin from brown seaweeds

Brown seaweeds contain a number of bioactive compounds. The xanthophyll, fucoxanthin, has in vivo efficacy against disorders such as type 2 diabetes, obesity and cancer. Organic solvents are traditionally employed to extract fucoxanthin, but carry a toxic chemical and environmental burden. The aim of this study was to optimise a fucoxanthin extraction method using enzymes, water, low‐temperature dehydration and mechanical blending, to produce yields comparable to those achieved with an organic solvent (acetone). Response surface methodology was applied, using Fucus vesiculosus as a model species. A fucoxanthin yield of 0.657 mg g^?1 (dry mass) was obtained from F. vesiculosus blade using the enzymatic method, equivalent to 94% of the acetone‐extracted yield. Optimum extraction parameters were determined to be enzyme‐to‐water ratio 0.52%, seaweed‐to‐water ratio 5.37% and enzyme incubation time 3.05 h. These findings may be applied to the development of value‐added nutraceutical products from seaweed.     

The efficiency and comparison of novel techniques for cell wall disruption in astaxanthin extraction from Haematococcus pluvialis

The efficiency of various techniques pulsed electric field (PEF), ultrasound (US), high‐pressure microfluidisation (HPMF), hydrochloric acid (HCl) and ionic liquids (ILs) for cell wall disruption in astaxanthin extraction from Haematococcus pluvialis was compared. The results indicated that ILs, HCl and HPMF treatment were shown the most efficient for cell disruption with more than 80% astaxanthin recovery. While the cell wall integrity of H. pluvialis cyst cell was less affected by US and PEF treatment. It was found that imidazolium‐based ILs showed the greater potential for cell disruption than pyridinium‐based and ammonium‐based ILs. Among all the ILs examined, 1‐butyl‐3‐methylimidazolium chloride ([Bmim] Cl) exhibited efficient cell disruption and capability of astaxanthin recovery at mild condition (pretreatment with 40% IL aqueous solution at 40 °C, followed by extraction with methanol at 50 °C) without extensive energy consumption and special facility requirement. In addition, recyclability of ILs was excellent.