Worawan Panpipat

Interrelationship between myoglobin and lipid oxidations in oxeye scad (Selar boops) muscle during iced storage

The interrelationship between myoglobin oxidation, lipid oxidation and discolouration in oxeye scad fish during iced storage were investigated. The myoglobin autoxidation rate increased with increasing storage time up to 12 days (p < 0.05) and remained constant thereafter (p > 0.05). Increase in metmyoglobin correlated well with a blue shift from 410 to 408 nm for myoglobin. The soret band of myoglobin decreased with a concomitant decrease in the redness index (p < 0.05). During storage, the extractable haem iron decreased (p < 0.05), while the non-haem iron increased (p < 0.05). Hydrogen peroxide and ferrylmyoglobin concentrations had increased at the end of storage (p < 0.05). The conjugated diene (CD) and peroxide value (PV) of oxeye scad lipids tended to stabilise during the initial phase of storage, increased in the differentiation phase and had declined at the end of storage. However, thiobarbituric acid reactive substances (TBARS) increased markedly (p < 0.05). Overall, lipid and myoglobin oxidations in oxeye scad occurred in a concurrent manner and each process appeared to enhance the other.

Chemical deterioration and discoloration of semi-dried tilapia processed by sun drying and microwave drying

ABSTRACT Drying methods can affect the chemical deterioration and discoloration of fish muscle. This study aimed to monitor the effect of microwave drying at different effective powers in comparison with sun drying on the physicochemical changes of semidried tilapia. Lipid deterioration, protein oxidation and discoloration of semidried tilapia (Oreochromis niloticus) muscle processed by sun drying and microwave drying were investigated. Results of the study revealed that the pH of microwaved tilapia was higher than that of the sun-dried tilapia (p < 0.05) and the pH increased with increasing microwave power (p < 0.05). The sun drying possessed higher degree of lipid oxidation as indicated by thiobarbituric acid-reactive substances (TBARS) with a greater level of lipolysis when compared to microwave drying (p < 0.05). Higher protein carbonyl content was in microwaved tilapia compared to sun-dried one (p < 0.05) and this content increased with increasing microwave power (p < 0.05). Sun drying resulted in a brown discoloration correlated with the highest metmyoglobin formation (p < 0.05), whereas microwave drying, particularly with high power, caused a green discoloration of semidried tilapia as revealed by a negative a* value with a significantly decreased redness index (p < 0.05). Therefore, lipid deterioration, protein oxidation and discoloration of semidried tilapia muscle were strongly influenced by drying methods.

Functional properties of pH-shifted protein isolates from bigeye snapper (Priacanthus tayenus) head by-product

ABSTRACT The functional properties of pH-shifted protein isolates from bigeye snapper head were evaluated. Alkaline isolate showed a superior salt-solubility and gel forming ability to acid counterpart as indicated by a regular gel structure (i.e., imaged by scanning electron microscope) with higher gel strength and lower expressible drip (p < 0.05). Acid isolate exhibited higher surface hydrophobicity (p < 0.05) and thereby improved interfacial properties. Emulsifying activity index of acid isolate was lower than commercial whey protein and egg-white (p < 0.05) but its emulsion stability was better (p < 0.05). Both protein isolates had lower foamability than commercial proteins but their foam stability was not different (p > 0.05).

Removal of Lipids, Cholesterol, Nucleic Acids and Haem Pigments During Production of Protein Isolates from Broiler Meat Using pH-shift Processes

Abstract The effect of acid and alkaline pH shift processes on removal of total lipids, cholesterol, nucleic acids and haem pigments during production of protein isolates from broiler meat was investigated. The gel-forming ability of resulting protein isolates were evaluated in comparison with raw broiler meat and water washed broiler meat. Significant reduction of total lipids, cholesterol, nucleic acids and haem proteins was obtained from both pH shift processes (p < 0.05). Acid process recovered more protein with less total haem pigments resulting in a greater breaking force and whiteness of the isolate gel compared to alkaline counterpart (p < 0.05). However, protein isolate gels showed inferior deformation and water holding capacity to washed mince gel (p < 0.05). Therefore, the pH shift processing could be used to produce a functional protein isolate with low nucleic acids, haem pigments and lipids and, thereby, reduced cholesterol level. The protein isolates, particularly acid version, still had good gelling properties.

Autolysis and Characterization of Sarcoplasmic and Myofibril Associated Proteinases of Oxeye Scad (Selar boops) Muscle

ABSTRACT The autolytic profile of oxeye scad mince was characterized. Mince showed higher proteolytic activity than washed mince. The highest autolysis was observed at 65 and 60°C for mince and washed mince, respectively. Both mince and washed mince showed the optimum pH for autolysis at pH 9.0, and their activities decreased with increasing NaCl concentration (0–3.5%). Autolysis of washed mince was markedly inhibited by soybean trypsin inhibitor (SBTI), suggesting that myofibril-associated proteinase was serine proteinase. Sarcoplasmic proteinase was characterized to be heat-activated alkaline proteinase having the optimal pH and temperature of 9.0 and 60°C, respectively. The activities were stable at pH range of 8.0–11.0 at 20–40°C. The crude proteinase was inhibited by N-p-tosyl-L-lysine chloromethyl ketone, SBTI, and phenylmethanesulfonyl fluoride, suggesting the predominance of serine proteinases, especially trypsin. NaCl suppressed the activity while β-mercaptoethanol, dithiothreitol, and CaCl2 activated the activity. Therefore, trypsin-like proteinase is a major endogenous proteinase responsible for autolysis in oxeye scad muscle. The present results can be used as scientific guidelines to predict the gel strength of surimi made from oxeye scad muscle.

Chapter 11 – Ionic Liquids in the Synthesis of Sugar/Carbohydrate and Lipid Conjugates

Carbohydrate fatty acid esters can be synthesized from esterification of sugars or polysaccharides with fatty acids by chemical and enzymatic reactions. These compounds are increasingly used as active biosurfactants in several applications. Nowadays, the interest for synthesis of sugar/carbohydrate and lipid conjugates is increasing. These compounds are widely used in food, cosmetic, detergent, and pharmaceutical industries. This chapter gives a survey on the latest most representative developments and progress concerning ionic liquids as media for synthesis of sugar/carbohydrate and lipid conjugates. It also highlights their emerging production strategies and also their applications.

4 – Palm Phospholipids

Publisher Summary Phospholipids play two major roles in palm oil: as an antioxidant synergist and a surface active agent to disperse impurities in oil. Phospholipids are the polar lipids that constitute an important part of cellular membranes and possess unique structures containing both lipophilic and hydrophilic functions. These naturally occurring emulsifiers can bind oil molecules together, leading to increased viscosity and refining and/or flow losses. Phospholipids of palm oil are receiving considerable attention because of the suspected deleterious effect of phosphorus on oil quality and they must be removed from the oils via a series of steps and processes that together are called refining. Phospholipids are high value-added products. Now-a-days, they have been recognized as being one of the major groups of food emulsifiers. Thus, recovery of phospholipids from palm-based products, such as crude palm oil, palm-pressed fiber and palm oil mill sludge is very significant and challenging. This chapter provides an overview of the recovery, occurrence and functional and nutritional properties of palm phospholipids.