Changes of Proximate Composition and Extractive Components In

Narezushi, A Fermented Mackerel Product, During Processing

SUBMITTED BY:Nazmul Ahmed oliReg:12-05-2835Level: lVCourse code: FIT-431Autumn term’15

SUBMITTED TO:Dr. A.K.M. AZAD SHAHASSOCIATE PROFESSOR,DEPT. OF FISHERIES TECHNOLOGY,FAACULTY OF FISHERIES,BSMRAU

INTRODUCTION:Narezushi:

Japanese food

Made by salting fish, pickling it with rice, and then pressing it while it undergoes lactic acid formation.

Fig: Narezushi

FISH USED:

1. River fish: Dace and sweetfish2. Saltwater fish: Horse mackerel, mackerel,

hachime, salmon and small sea bream.

MATERIALS AND METHODS:

Preparation of Mackerel Narezushi:

350±50 g fresh raw mackerel were gutted & washed.Add 5% NaCl and placed for 2 days at 5°C.Rinsed well with tap wate & add rice mixture that was prepared by adding 7.3% NaCl and 10% Japanese sake.covered with 70% rice mixture + a small amount of Japanese pepper leaves, Piled in a 100-L plastic barrel & filled with brine. (5% NaCl).Kept 4 months for the final product.

Body weigh measurement:By an electric balance

pH Determination: 5 g sample + 15ml distilled water homogenized &

measured by pH meter. NaCl content:

5 g sample + 20 ml distilled water homogenized & measured by digital salt meter.

Component Determination

Moister Difference of the sample weight after drying at 105°C for 20 h

Ash Heating the sample to a constant weight at 600°C.

Protein Semi-micro Kjeldahl method

LipidExtracting the sample with a chloroform–methanol mixture (2:1) and then by weighing after evaporating the chloroform layer.

CarbohydrateSubtraction of moisture, protein, lipid, and ash contents from the total weight.

Determination of organic acids isotachophoretic apparatus used (pore size is 0.45μm)

Determination of free amino acids and peptides PCA extracts were resolved in 0.02 N HCl and filtered through a

membrane filter . The free amino acid contents in the filtrate were determined using an

amino acid analyzer

Determination of ATP-related compounds 5 compound were found:

adenosine 5′-diphosphate (ADP), 5′-adenylic acid (AMP), 5′-inosinic acid (IMP), inosine (HxR), and hypoxanthine (Hx)

RESULTS AND DISCUSSION Changes in proximate composition Shrinkage during the salting and fermentation process

Fig: 2 Changes in proximate composition in (a) mackerel, and (b) rice mixture during the processing of narezushi.

Moister content : In fish meat moisture decrease 67 to 63% during

the 2 days 57% during 30 days it maintained a plateau from 30–120 days of

fermentation. The moisture content of the rice conversely

increased from 58 to 63% for up to 10 days of fermentation and then formed a plateau.

The protein content is 23% of the raw

mackerel, did not change markedly

In the rice mixture protein is 2.3% before fermentation, slowly

increased to 8.8% until 60 days of

fermentation.

The lipid content of the raw mackerel

decreased slightly from 9 to 7.5% during the 2

days of salting,

lipid content of the rice mixture was 0.2%

before fermentation and it did not exceed

0.5%

Changes in pH and organic acid contents

Raw mackerel meat was pH 6.05 & did not change during the 2 days of salting

decreased rapidly to pH 4.90 at 20 days, slowly to 4.51 from 20–60 days

and little after 60 days during the fermentation

Fig. 3 Changes in pH in mackerel (•) and rice mixture (■) during the processing of narezushi.

Organic acid content increased from 1.1 to 1.4 g/100 g during the 2 days

rapidly increased to 5.9 g/100 g during the 120 days

Figure 4a shows the changes in the organic acid contents in mackerel meat.

Figure 4b shows the changes in organic acid content in the rice mixture.

• Lactic acid increased to 3.3 g/ 100g • Acetic acid, which rapidly

increased to 1.4 g/100 g at 10 days & decreased to 0.3 g/100 g at 20 days and then slightly increased to 0.6 g/100 g

Changes in free amino acid

Fig. 5 Changes in peptide (■ ) and free amino acid (•) contents in (a) mackerel, and (b) rice mixture during the processing of narezushi.

• Free amino acids was 0.70 g/100 g in raw mackerel,

• increased to 0.80 g/100 g during the 2 days

• Further increased to 3.2 g/100 g during 60 days of fermentation and then it changed little from 60–120 days.

Peptide content in rice mixture: Increase from 0.1 to 1.5 g/100 g until 60 days of

fermentation, And then it changed little from 60– 120 days.

Changes in Peptide content

glutamic acid (Glu), leucine (Leu), lysine (Lys), aspartic acid (Asp), and alanine (Ala) markedly increased in mackerel.

Changes in ATP-related compounds

Fig. 6 Changes in the content of ATP-related compounds ATP (●), ADP (■), AMP (▲), IMP (♦), HxR (), and Hx () in (a) mackerel, and (b) rice mixture during the processing of narezushi.

ATP, ADP, and AMP were very low

IMP was 280 mg/100 g HxR rapidly increased

from 71 mg/100 g to 160 mg/100 g with a decrease in IMP during 2 days of salting,

And then it also became entirely absent at 60 days of fermentation.

The rice mixture contained negligible levels of nucleotides, 4.1 mg/100 g of HxR and 6.2 mg/100 g of Hx at the start of fermentation

Hx increased to 54 mg/100 g at 20 days of fermentation, then it decreased to 22 mg/100 g.

Hx is reported to be a bitter taste component rather than a taste-active component in marine resources

Conclusion

The extractive components such as free amino acids, peptides, and organic acids remarkably increased during the processing of narezushi, while nucleotides were entirely lost. Their remarkable increases are concluded to be responsible for the taste of narezushi

Thanks Everybody