CHEMICAL AND MICROBIOLOGICAL QUALITIES OF DRY-SALTED (LAKERDA) BONITO (SARDA SARDA, BLOCH 1793)

In this study, changes in the chemical and microbiological properties of bonito (Sarda sarda, Bloch 1793) salted by dry salting (lakerda) and stored for 6 months at 4 ± 1C were investigated. The fresh gutted and sliced bonitos were used as raw material for salting by using the ratio of fish to salt as 5:1 by weight. Salted fish remained in the liquid pickle formed by salt and the liquid extracted from the fish. This solution was not drained during the storage period. The product is described as “lakerda” in Turkey. In the fresh fish, total volatile basic nitrogen (TVB‐N) and trimethylamine nitrogen (TMA‐N) values were 11.21 mg/100 g and 1.19 mg/100 g, respectively. During the storage period, TVB‐N and TMA values increased slowly to 27.67 mg/100 g and 4.99 mg/100 g, respectively, at the end of the storage period. In the first month after salt processing, the total mesophilic bacteria count was 4.6 × 10² cfu/g. In the later months, mesophilic, psychotropic, coliform bacteria and yeast‐mold did not reproduce. According to the results, bonito salted by dry salting and stored at 4 ± 1C was in good quality in terms of chemical and microbiological properties during the storage period of 6 months.     

SHELF LIFE AND BIOCHEMICAL COMPOSITION OF BONITO FISH (Sarda sarda, BLOCH, 1758) STORED AT 4C AND FISHING WITH DIFFERENT FISHING TOOLS

This study was carried out to determine the effects of harvesting method and refrigerated storage on biochemical composition of Atlantic Bonito. Samples were fish caught with a surround trammel net and a drift net in the Middle Black Sea region by fisherman and were brought to the laboratory. Quality control analyses for soluble solid, protein, fat and ashes were performed. On the 10th day after refrigerated storage (4C), pH, total volatile base nitrogen (TVB-N), trimethylamine (TMA-N) and thiobarbituric acid (TBA) values were found in the drift net. In the fresh fish samples caught by surround trammel net and drift net, fat, proteins, soluble solids and ash contents were calculated.

PRACTICAL APPLICATIONS

The results of the proximate content of Atlantic bonito caught with a trammel net and drift net showed that fat contents were 5.76; protein contents were 20.35; dry matter contents were about 30.5% and ash contents was 1–1.2%. After 10 days of storage at 4C, pH, TVB-N, TMA-N and TBA values were 6.17, 34.46 mg/100 g, 7.34 mg/100 g and 7.72 mg malonaldehyde/kg, respectively, in the surround trammel net, and 5.98, 40.60 mg/100 g, 8.02 mg/100 g and 8.03 mg malonaldehyde/kg in the drift net, respectively. Based on these results, there were significant differences between surround trammel net fishing and drift net fishing in terms of meat quality.     

IMPROVING THE QUALITY AND SHELF LIFE OF TURKISH ALMOND PASTE

Almond paste is an economically valuable product produced from almonds, sugar and a small amount of water. Oxidative rancidity and oil separation are the major problems that are encountered in the paste products affecting the shelf life. Another problem appears to be drying on the surface of the product resulting in poor consumer acceptability. In this study, the formulation of product was altered by adding a commercial stabilizer, antioxidant mixture and maltose syrup to prevent undesirable quality changes during storage at 4C and 30C. Peroxide value, free fatty acid and Rancimat analysis showed that the addition of antioxidant mixture prevented oxidation effectively and improved sensory scores significantly ( P ≤  0.05). Although stabilizer addition had a detrimental effect on the textural properties, samples that have maltose had high sensory scores. The results showed that incorporation of maltose syrup and antioxidant may improve the texture and shelf life of almond paste.

PRACTICAL APPLICATIONS

The available literature on almond paste is mainly focused on the microbiological quality of the product and the prevention of spoilage reactions by modifying packaging materials. However, there is no report on the optimization of the composition to extend the shelf life of almond paste. Turkish almond paste, a healthy and expensive dessert, is a specialty product that is manufactured by using traditional grinding equipment. However, the limited shelf life of this product decreases its export potential resulting in economical losses. Therefore, improved shelf life and quality of the product is of importance from the economical point of view. In our study, we aimed to improve the quality and shelf life of Turkish almond paste by modifying its formulation in order to minimize the undesirable changes that occur during storage.     

CHANGES IN BIOGENIC AMINE CONTENTS AND SENSORY QUALITY OF SARDINE (SARDINA PILCHARDUS) STORED AT 4C AND 20C

Biogenic amines (tyramine, putrescine, cadaverine, histamine, spermidine and spermine) in sardine during the storage at two temperatures (4C and 20C) were investigated. Changes in sensory scores were also recorded. Significant differences between storage times were found. The levels of tyramine, putrescine, cadaverine and histamine increased as decomposition of sardine progressed at both 4C and 20C. Spermidine and spermine did not change throughout storage. Putrescine was the main biogenic amine formed, followed by tyramine, cadaverine and histamine. Histamine remained lower than the toxic level of 100 mg/kg in the samples stored at 4C whereas it exceeded the toxic level after 16 h at 20C. The increase in histamine concentration was lower than tyramine and putrescine at both temperatures. Sensory scores gradually decreased during the storage.     

INFLUENCE OF VACUUM PACKAGING AND ORGANIC ACID TREATMENT ON THE CHILLED SHELF LIFE OF PEARL SPOT (ETROPLUS SURATENSIS, BLOCH 1790)

The present work was carried out to study the effect of vacuum packaging and organic acids drip treatment, namely, sodium acetate and potassium sorbate (2%), on the quality of pearl spot during chilled storage (1–2C). Changes in pH, drip loss, water-holding capacity, total volatile base nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), total plate counts, instrumental texture properties and sensory characteristics were investigated up to 18 days. Sensory evaluation revealed that the potassium sorbate- and sodium acetate-treated vacuum-packaged samples had good sensory characteristics up to 16 days compared with 7 days in control air packs (CAPs) and control vacuum packs (CVPs). The sensory shelf life followed the following order: CAP  <  CVP  <  sodium acetate-treated vacuum pack  <  potassium sorbate-treated vacuum pack. Chemical analysis demonstrated a significant ( P   <  0.05) reduction in TVB-N, TMA-N and total plate counts, and better textural properties in potassium sorbate- and sodium acetate-treated vacuum-packaged fishes than CAPs and CVPs.

PRACTICAL APPLICATIONS

Limited shelf life is one of the major problems the seafood industry faces today. The study compares the effect of vacuum packaging in combination with preservative chemical treatment on the shelf life of pearl spot. The study indicates that the use of chemical preservative treatments such as sodium acetate and potassium sorbate at 2% level, together with vacuum packaging, helps in extending the shelf life of pearl spot to 16 days compared with 7 days in control air packs and control vacuum packs. Hence, vacuum packaging, together with preservative treatment, is very effective in shelf-life extension compared with vacuum packaging alone.     

QUALITY OF FROZEN/THAWED SPRAT (SPRATTUS SPRATTUS SPRATTUS) STORED IN CLING FILM AND ALUMINUM FOIL AT 4C1

Frozen sprats (Sprattus sprattus sprattus) were thawed and separated into three lots: two lots were wrapped and kept chilled in a refrigerator at 4C, one wrapped in aluminum foil (AF), the other in cling film (CF) and a third lot left unpackaged and held in melting ice. Biochemical tests, performed at intervals over a 16‐day period, showed better quality and an extension of shelf‐life for sprats stored unpackaged in ice compared with those held at 4C packed in AF or CF. The levels of trimethylamine oxide‐nitrogen (TMAO‐N) decreased throughout storage and significant differences (P<0.05) were observed between the lot in ice and the lots stored in AF or CF (P<0.05). However, significant differences (P<0.05) were not observed between AF and CF lots during the experiment. Increases in total volatile base nitrogen (TVB‐N) and trimethylamine‐nitrogen (TMA‐N) were significantly retarded, as were reductions in sensory quality, in the ice‐stored fish compared with packaged, refrigerated fish.     

PHYSICOCHEMICAL PROPERTIES OF MUSCLE AND NATURAL ACTOMYOSIN EXTRACTED FROM FARMED ATLANTIC SALMON (SALMO SALAR) STORED AT 4C

Properties of farmed Atlantic salmon (Salmo salar) obtained commercially were studied as a function of storage at 4C for 9 days. While pH increased gradually during storage for both samples, significant differences between samples were noted in water‐binding capacity (WBC) of muscle, as well as surface hydrophobicity (S_o) and sulfhydryl contents of extracted natural actomyosin (NAM). Lower S_owas observed for NAM extracted from muscle stored for 2 days, coinciding with high WBC of the muscle. In contrast, higher S_ofrom 5 to 7 day‐stored samples coincided with minimum extractability and high apparent viscosity of NAM. Reactive sulfhydryl groups were higher at the beginning and end of storage. Generally, WBC of fish muscle was dependent on pH and related to changes in S_oof NAM, while apparent viscosity increased with S_oand disulfide content. The results indicate variability in functional properties of the salmon samples during cold storage, which could be attributed to changes in physicochemical properties of NAM.     

TEXTURAL AND SENSORY PROPERTIES OF α-AMYLASE TREATED POI STORED AT 4C

Poi, a purplish paste made of cooked taro (Colocasia esculenta), hardens rapidly to a rubbery gel at a refrigeration temperature of 4C. This gelling phenomenon was averted by an addition of α-amylase in poi prior to refrigeration. Two sources (porcine pancreas and Aspergillus oryzae) of the enzyme were compared at usage levels of 200 units and 2,000 units. Both the viscosity readings and textural analyses indicated that the enzymatic treated poi maintained a fresh-poi like softness. The α-amylase from porcine pancreas exhibited the least effect at the 200 unit level, while the α-amylase from Aspergillus oryzae caused a slight thinning of the starch staple. The sensory evaluation indicated that the textural attributes were in agreement with the instrumental measurements. Their flavor profiling indicated a loss of the taro taste, however, no off-flavor was observed from the enzymatic treatment at 4C for up to seven days.     

QUALITY CURVES FOR MANGO FRUIT (CV. TOMMY ATKINS AND PALMER) STORED AT CHILLING AND NONCHILLING TEMPERATURES

“Tommy Atkins” and “Palmer” mangoes were harvested medium‐ripe held for 7–20 days at five different temperatures and evaluated for quality attributes. The objective of this work was to obtain quality curves at chilling and nonchilling temperatures and to identify, for each temperature, which quality factors limit mango marketability. Chilling injury and increased fruit softness were the limiting quality factors for mango stored at 2 and 5C. Softening of the fruit, changes in color and development of decay were the limiting quality factors for mango stored at 12, 15 and 20C. Prediction of mango shelf life calculated from the data reported in the literature is not precise unless the characteristics of the fruit and environmental factors involved are well known. The curves obtained from quality evaluations for each temperature showed that a single quality attribute cannot be used to express loss of quality of mango over the normal physiological range of temperatures.     

POSTMORTEM BIOCHEMICAL AND TEXTURAL CHANGES IN THE ADDUCTOR MUSCLE OF CATARINA SCALLOP STORED AT 0C

Postmortem characteristics of the adductor muscle of the Catarina scallop were evaluated for biochemical, chemical and textural changes during a 15‐day storage period in ice (0C). K‐value, pH, nitrogen of trimethylamine (TMA‐N), nitrogen of total volatile bases (TVB‐N), water‐holding capacity (WHC), color and texture changes were monitored. K value increased linearly from an initial value of 20.5 to 68.5% at day 15. Spoilage indicators TVB‐N and TMA‐N (mg/100 g) increased from 13.5 and 2.6 to 21.4 and 3.4, respectively. However, they remained below critical limits, suggesting low microbial activity. In contrast, texture, pH, WHC, and color were not affected. Overall results indicated that the quality of iced Catarina scallop adductor muscle packed in ice was maintained over a period of 15 days.