Pineapple wastes: A potential source for bromelain extraction

This study investigates the isolation and characterization of bromelain extract from the wastes of Nang Lae and Phu Lae pineapple cultivars (economical fruits of Chiang Rai province, Thailand). The waste portions such as the peel, core, stem and crown were 29–40%, 9–10%, 2–5% and 2–4% (w/w), respectively. The extract of crown from both cultivars gave the highest proteolytic activity and protein contents, while the extract from the stem exhibited the lowest values. SDS–PAGE showed that the major protein band in the extracts was ～28 kDa. Activity staining of the crown extracts from both cultivars confirmed that the major protein band showed caseinolytic activity on the casein substrate-gel. All of the crude extracts from both cultivars gave high caseinolytic activity (>80% relative) in a board pH range (3–9). The optimum temperatures for all crude extracts were about 50–60 °C. This study founded that there is much added value into local Thailand pineapple wastes because of bromelain extraction.     

Optimizing the Tyrosinase Inhibitory and Antioxidant Activity of Mango Seed Kernels with a Response Surface Methodology

This study describes the optimization of polyphenol extraction from mango seed kernels by using response surface methodology (RSM). In the solid-to-liquid selection, the extraction yield, total phenolic content (TPC), antioxidant activity, and tyrosinase inhibitory activity are all significantly increased with a decrease in the solid-to-liquid ratio (P?<?0.05). Between the Nam-Dok-Mai kernel (NDK) and the Tong-Dam kernel (TDK), the TDK was chosen for RSM with a fixed ratio of 1:30 solid-to-liquid. The variables in the independent processing were the concentrations of ethanol, the temperature, and the time applied to RSM. Ethanol concentration, temperature, and duration had significant individual and interactive effects on phenolic yield and antioxidant activities (P?<?0.05). The optimized condition that maximized the extraction yields, TPC, and antioxidant activities from TDK was an ethanol concentration of 62 %, a temperature of 63 °C, and a duration of 150 min. The obtained and validated optimized model could be used to describe the effect of these variables on the extraction of phenolic compounds from mango seed kernels.     

Assessment of protein changes in farmed giant catfish (Pangasianodon gigas) muscles during refrigerated storage

Farmed giant catfish (Pangasianodon gigas) muscles (dorsal and ventral sites) were stored in a refrigerator (at 4 °C) for 14 days to determine the effect of refrigerated storage on biochemical and physical changes. The analyses were carried out at 0, 2, 4, 7, 10 and 14 days of storage. At day 14, Ca²⁺ ‐ATPase activity markedly decreased when compared to its value at day 1 (>90%), while a small decrease was observed for surface hydrophobicity and reactive sulfhydryls content. Total volatile basic nitrogen and trichloroacetic‐soluble peptide content gradually increased when the storage period was extended. The myosin heavy chain decreased slightly on SDS‐PAGE for both meat cuts with increased storage time. Expressible drip and cooking loss were highest during the first day of storage and slightly decreased with storage time. Instrumental hardness was significantly higher in the ventral compared to the dorsal muscle, while the toughness was the highest at the second day of storage. The muscle bundles with scanning electron microscopy were less attached, resulting in the observed big gaps over increasing storage time. Results indicated that changes of proteins have detrimental effects on the quality attributes of farmed giant catfish muscles during refrigerated storage, particularly physical and biochemical properties.     

Whey protein concentrate: Autolysis inhibition and effects on the gel properties of surimi prepared from tropical fish

Effects of whey protein concentrate (WPC) on autolysis inhibition and gel properties of surimi produced from bigeye snapper (Priacanthus tayenus), goatfish (Mulloidichthys vanicolensis), threadfin bream (Nemipterus bleekeri) and lizardfish (Saurida tumbil) were investigated. WPC (0–3%) showed inhibitory activity against autolysis in all surimi at both 60 and 65 °C in a concentration-dependent manner. Myosin heavy chain (MHC) of surimi was more retained in the presence of WPC. Breaking force and deformation of kamaboko gels of all surimi increased as added levels of WPC increased (P < 0.05). This was associated with lower levels of protein degradation, as evidenced by the decrease in trichloroacetic acid-soluble peptide content (P < 0.05). WPC at 3% (w/w) significantly decreased the whiteness of gels. However, water-holding capacity of kamaboko gels was improved with increasing concentration of WPC. The microstructure of surimi gels generally became denser with the addition of WPC.     

Chemical compositions and characteristics of farm raised giant catfish (Pangasianodon gigas) muscle

Proximate composition, chemical and physical properties of dorsal, ventral and lateral line cuts of farm raised giant catfish were determined. Protein, fat and ash content of the different cuts averaged 16.88, 4.45 and 1.24 g/100 g, respectively. Dorsal contains higher protein concentrations (19 g/100 g) than other two parts (p < 0.05). Ventral showed the highest hydroxyproline content (0.83 mg/g). Differences in lipid composition and fatty acid profiles were found among different cuts with highest phospholipids in the dorsal and highest triglyceride in both ventral and lateral line (p < 0.05). All the meat cuts contained high saturated fatty acid, followed by mono- and polyunsaturated fatty acid. High muscle hardness and toughness was found in the dorsal than that in the ventral (p > 0.05). The highest content of myoglobin and total pigment in lateral line resulted in the highest redness index (a*/b*) of this part. Three major nitrogenous compositions classified based on solubility in giant catfish muscle were myofibrillar, sarcoplasmic and alkaline soluble proteins.     

Properties of gelatin films from giant catfish skin and bovine bone: a comparative study

Edible films were prepared from the gelatin of farmed giant catfish skin (GC) (Pangasianodon gigas), bovine bone gelatin (BB) and their combination. The physical, mechanical, thermal and chemical properties of the resulting films were characterized and compared. The molecular weight distributions of the giant catfish skin gelatin-containing samples had high quantities of α-chains, β-components and high molecular weight cross-links. The bovine bone gelatin-containing samples showed low contents of major bands with high degradation band components. The GC films had higher water activity (0.45) and mechanical properties [tensile strength: TS 41 MPa and elongation at break: EAB 34 (%)] but lower thickness (38 μm) and water vapor permeability than those of BB films. The lowest light transmission (200–800 nm) and film transparency (3.34) were found in the GC films. However, the color attribute (L, a and b) of BB films was closer to the low-density polyethylene commercial film (ΔE 1.2). The highest value of film and protein solubility (100%) was found in BB film, while the lowest value (41–56%) was found in GC film. The GC films showed the most compact, smooth and continuous surface without porous structures, which corresponds to the greater properties of films.     

The properties of gelatin film‐neem extract and its effectiveness for preserving minced beef

The properties of gelatin films developed from neem extract (NE; Azadirachta indica) were determined. Moreover, the developed films were applied to minced beef to test its effectiveness for preserving the meat. The quality attributes of the minced beef wrapped with the developed film were monitored over a 7‐day period in refrigerated storage (4 ± 1°C) and were compared to a control commercial wrap film (polyvinyl chloride). The addition of NE improved the elongation at break, solubility, and antioxidant activity of the gelatin films. After 7 days of storage, the minced beef wrapped with the experimental film showed the highest a* and weight loss values. Gradually, changes in TBARS were more pronounced in the experimental sample. It was concluded that gelatin film containing NE is a potentially promising film that could help delay oxidative reactions. However, some characteristics of the film (eg, mechanical properties and water vapor permeability) need to be improved before putting them to commercial use.     

Biodegradable Protein‐based Films and Their Properties: A Comparative Study

Biodegradable protein‐based films prepared from different protein sources [commercial bovine gelatine (CG), giant catfish skin gelatine (GG), soy protein isolates (SPI), fish myofibrillar protein (FMP) and whey protein concentrate (WPC)] were all investigated for their mechanical, physical, chemical, thermal and barrier properties. The properties of the resulting films were then compared with those of commercial wrap films [polyvinyl chloride (PVC)]. The film forming solution containing 7% (w/v) protein and 50% (w/w) glycerol was used to produce the films through a casting method. Of the protein‐based films, the GG film had the highest tensile strength and elongation, while the WPC film exhibited the lowest film solubility, water vapour permeability, light transmission in UV‐Vis range (200–800 nm) and film transparency. However, the colour of the FMP film and the thickness were closer to that of the PVC film, particularly the L* and b* values. The appearances of the protein‐based films were similar to the PVC film, and they were uniformly transparent. Therefore, biodegradable films produced from different types of protein sources exhibited differences in their properties. These results are consistent with data from FTIR and protein pattern analyses. Based on these findings, different sources of protein‐based films can be used as an alternative for food packaging applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Trypsin Inhibitor from 3 Legume Seeds: Fractionation and Proteolytic Inhibition Study

ABSTRACT: The trypsin inhibitor from navy beans (Phaseoulus vulgaris), red kidney beans (Phaseoulus vulgaris L.), and adzuki beans (Vigna angularis) provided by the Royal Project Foundation in Thailand was isolated by heat and ammonium sulfate (AS) precipitation. Incubation at 70 °C for 10 min produced the highest trypsin inhibitor recovery for all legumes. The AS precipitation with 60% to 80% saturation (precipitate IV) resulted in 41-, 88-, and 34-fold of the purity and (−)26%, 126%, and (−)47% of percentage of activity increase for navy beans, red kidney beans, and adzuki beans, respectively. The trypsin inhibitors had a molecular weight of 132 kDa for navy beans, 118 kDa for red kidney beans, and 13 kDa for adzuki beans under nonreducing conditions. The obtained precipitate IV fraction from each legume effectively prevented the degradation of the tilapia muscle with concentration dependent. The myosin heavy chain increased as the concentration of the inhibitor fraction increased, especially at the highest level of addition. The result indicated that the precipitate IV from these legumes have potential for use as a protease inhibitor in fishery related products.