Changes in the quality of abalone (Haliotis asinina Linnaeus) packaged under atmospheric air,vacuum and modified atmosphere

Changes in the quality of abalone (Haliotis asinina Linnaeus) meat packaged under modified atmosphere (MA) of 40% CO2/30% O2/30% N2, vacuum and atmospheric air in polyvinylidene chloride (PVDC)/nylon/oriented polypropylene (OPP) pouches, and stored at 2 ± 1°C were investigated. Biochemical indices, such as pH, total volatile basic nitrogen (TVB‐N), and trimethylamine (TMA) and sensory evaluation, as well as total plate counts of packaged abalone meat were determined periodically. TMA was not affected by the packaging conditions, and remained low during storage periods. A decrease in pH of the MA packaged abalones during the storage reflected the apparent absorption of CO2. The content of TVB‐N slowly increased in the MA packaged abalone, whereas those stored in atmospheric air markedly increased during the storage. The sensory quality of MA packaged abalones was shown to be acceptable up to 15 days, while atmospheric and vacuum‐packaged abalones were not acceptable after 3 days of storage. Copyright © 2007 John Wiley & Sons, Ltd.     

Antioxidant and antimicrobial properties of Thai propolis extracted using ethanol aqueous solution

The potential of using propolis collected from Thailand as a natural antioxidant and antimicrobial agent for food applications was investigated. The propolis extract was prepared by using different ethanol aqueous solutions, including 30%, 40%, 50% and 70%. Total phenolic content (TPC), phenolic compound and antioxidant activity of the propolis were determined using Folin–Ciocalteau method, high performance liquid chromatography (HPLC) and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activity, respectively. The antimicrobial ability was tested against Staphylococcus aureus (TISTR 118), Salmonella enteritidis (DMST 17368), Escherichia coli (TISTR 780) and Pseudomonas aeruginosa (ATCC 27853) using disc diffusion technique. The major phenolic compounds found in Thai propolis were rutin, quercetin and naringin. The TPC and DPPH radical scavenging activity increased with increasing ethanol concentration in the solvent. Propolis extract showed antimicrobial activity, in terms of inhibitory zone for S. aureus and limited growth underneath paper discs, against all tested bacteria.     

Xanthan Production by Mutant Strain of Xanthomonas campestris TISTR 840 in Raw Cassava Starch Medium

Raw cassava starch was used as carbon source in growing Xanthomonas campestris TISTR 840 for xanthan production due to its cheap price and mass production in Thailand. However, xanthan production with raw cassava starch yielded low content (4.31 g/l). A low level of amylase was detected in the XOL medium of X. campestris when raw cassava starch was used. Treatment of X. campestris TISTR 840 with ethyl methansulfonate resulted in the isolation of Xc-M, a strain that showed highest amylase overproduction. When cultured in bioreactor with a medium containing raw cassava starch, the growth of Xc-M cells was significantly higher than that of the wild type. The mutant produced 3.46- and 1.39-fold increased amylase activity and xanthan yield, respectively. Xc-M is useful for xanthan production in media containing raw starch as a carbon source.     

Protein hydrolysate from tilapia frame: antioxidant and angiotensin I converting enzyme inhibitor properties

The effect of varying the aminopeptidase concentration and hydrolysis time in the production of a protein hydrolysate from tilapia frame (TFPH) was evaluated in terms of the obtained antioxidant and angiotensin I converting enzyme (ACE) inhibitor activities. Minced tilapia frame was subjected to hydrolysis using three concentrations Flavourzyme^® 1000 L [Brenntag Ingredients (Thailand) Company Limited (Public), Bangkok, Thailand] [0%, 1% and 2% (w/w)] and two hydrolysis times (0 and 1 h). The enzyme concentration and hydrolysis time both significantly affected the antioxidant and ACE inhibitor properties. The use of 2% (w/w) Flavourzyme^® 1000 L for 1 h yielded the highest levels of 2,2‐diphenyl‐1‐picrylhydrazil free radical scavenging (90.4%), metal chelating (91.8%), thiobarbituric acid activity ratio (81.9%), and ACE inhibition (83.8%). In addition, this TFPH contained a higher net amount of amino acids and a larger peptide molecular weight distribution compared to the unhydrolysed tilapia frame supernatant. Thus, TFPH may be a suitable supplement to improve the functionality of food products.     

An alternative freshness index method for modified atmosphere packaged abalone using an artificial neural network

An alternative freshness index method for abalone (Haliotis asinina) muscle packaged under atmospheric air (Air) and modified atmosphere (MA) of 40% CO₂: 30% O₂: 30% N₂ packaging conditions and stored at 2 ± 1 °C was developed. Biochemical indices covering pH, total volatile basic nitrogen (TVB-N), trimethylamine (TMA) and nucleotide degradation products, as well as instrumental texture and color of the packaged abalones, were determined. Sensory characteristics including odor, color and appearance were evaluated and then summarized into overall freshness scores (freshness index). The biochemical and instrumental analyses were then calibrated with the freshness index, using an artificial neural network algorithm. The neural network was shown to be capable of correlating biochemical and instrumental analyses with the freshness index. A useful prediction was possible, as measured by a low mean square error (MSE = 0.092) and a regression coefficient (R² = 0.98) between true and predicted data.     

Structure and functional properties of modified threadfin bream sarcoplasmic protein

Surimi wash-water contains up to 30% of protein from fish muscle that is currently underutilized. This paper describes the effect of acetylation, succinylation, trypsin hydrolysis or pre-heating at 55 °C on the emulsification and foaming properties of a threadfin bream sarcoplasmic protein (TBSP) model for wash-water protein. Multiple regression analysis showed that emulsification and foaming characteristics were differentially affected by TBSP surface hydrophobicity (S₀), solubility in water (S_W) and free amino group (fNH₂) concentration. Emulsification activity index (EAI) for TBSP was most enhanced by succinylation, whereas the foaming capacity (FC) was more effectively extended by trypsin hydrolysis. Structure–function relationships for emulsification were different from those associated with foaming or for ensuring the stability of these food dispersions. This study suggests that surimi wash-water protein functionality can be improved by protein modification. Further strategies may be needed to stabilize fish protein stabilized emulsions and foams.