Search results for: proteolysis

Authors: I. Fathollahi, J. Hesari, S. Azadmard, S. Oustan

Abstract:

The relationships between Proteolysis and soluble calcium levels with hardness of cheese texture were investigated in Iranian UF white cheese during 90 d ripening. Cheeses were sampled in interior and exterior. Results showed that levels of proteolysis, soluble calcium and hardness of cheese texture changed significantly (p< 0.05) over ripening. Levels of proteolysis and hardness were significantly (p< 0.05) different in interior and exterior zones of cheeses. External zones of cheeses became softer and had higher levels of proteolysis compared to internal zones during ripening. The highest correlation coefficient (r2= 0.979; p<0.01) was observed between hardness and levels of pH 4.6-soluble nitrogen in exterior zones of cheese. These result showed that proteolysis can contribute to textural softening during ripening of Iranian UF white cheese.

Keywords: Calcium, Proteolysis, Softening, Ultrafiltration, White cheese.

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Authors: P. M. Ikonić, T. A. Tasić, L. S. Petrović, S. B. Škaljac, M. R. Jokanović, V. M. Tomović, B. V. Šojić, N. R. Džinić, A. M. Torbica, B. B. Ikonić

Abstract:

The aim of the study was to determine how different ripening processes (traditional vs. industrial) influenced the proteolysis in traditional Serbian dry-fermented sausage Petrovská klobása. The obtained results indicated more intensive pH decline (0.7 units after 9 days) in industrially ripened products (I), what had a positive impact on drying process and proteolytic changes in these samples. Thus, moisture content in I sausages was lower at each sampling time, amounting 24.7% at the end of production period (90 days). Likewise, the process of proteolysis was more pronounced in I samples, resulting in higher contents of non-protein nitrogen (NPN) and free amino acids nitrogen (FAAN), as well as in faster and more intensive degradation of myosin (≈220 kDa), actin (≈45 kDa) and other polypeptides during processing. Consequently, the appearance and accumulation of several protein fragments were registered.

Keywords: Dry-fermented sausage, Petrovská klobása, proteolysis, ripening process.

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Authors: Mohammad B. HabibiNajafi, Saeideh Sadat Fatemizadeh, Maryam Tavakoli

Abstract:

In recent years, the consumption of functional foods, including foods containing probiotic bacteria, has come to notice. Milk proteins have been identified as a source of angiotensin-I-converting enzyme )ACE( inhibitory peptides and are currently the best-known class of bioactive peptides. In this study, the effects of adding prebiotic ingredients (inulin and wheat fiber) and fat percentage (0%, 2% and 3.5%) in yogurt containing probiotic Lactobacillus casei on physicochemical properties, degree of proteolysis, antioxidant and ACE-inhibitory activity within 21 days of storage at 5 ± 1 °C were evaluated. The results of statistical analysis showed that the application of prebiotic compounds led to a significant increase in water holding capacity, proteolysis and ACE-inhibitory of samples. The degree of proteolysis in yogurt increases as storage time elapses (P < 0.05) but when proteolysis exceeds a certain threshold, this trend begins to decline. Also, during storage time, water holding capacity reduced initially but increased thereafter. Moreover, based on our findings, the survival of Lactobacillus casei in samples treated with inulin and wheat fiber increased significantly in comparison to the control sample (P < 0.05) whereas the effect of fat percentage on the survival of probiotic bacteria was not significant (P = 0.095). Furthermore, the effect of prebiotic ingredients and the presence of probiotic cultures on the antioxidant activity of samples was significant (P < 0.05).

Keywords: Yogurt, proteolysis, ACE-inhibitory, antioxidant activity.

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Authors: H. Rasouli Pirouzian, J. Hesari, S. Farajnia, M. Moghaddam, S. Ghiassifar, M. Manafi

Abstract:

Lighvan cheese is basically made from sheep milk in the area of Sahand mountainside which is located in the North West of Iran. The main objective of this study was to investigate the effect of enterococci isolated from traditional Lighvan cheese on the quality of Iranian UF white during ripening. The experimental design was split plot based on randomized complete blocks, main plots were four types of starters and subplots were different ripening durations. Addition of Enterococcus spp. did not significantly (P<0.01) affect the pH and gross composition of cheeses. In the cheeses produced with Ent. faecalis and Ent. faecium strains, lipolysis rates were higher and flavor were improved. Moreover, proteolysis assay by measuring percentage of soluble nitrogen at pH 4.6 and urea polyacrylamide gel electrophoresis indicated the increase in proteolysis rate in the cheese containing Ent. faecalis and Ent. faecium strains compared to the control cheeses. Furthermore, the highest percentage of non- protein nitrogen was observed in the cheese containing Ent. faecium. In conclusion, the results showed the positive effect of the Ent. faecalis and Ent. faecium on secondary proteolysis, lipolysis and sensorial characteristics development of UF white cheeses.

Keywords: Enterococcus faecalis, Enterococcus faecium, Lighvan cheese, Lipolysis, Proteolysis, UF cheese

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Authors: Zainoldin, K.H., Baba, A.S.

Abstract:

Yogurt is a coagulated milk product obtained from the lactic acid fermentation by the action of Lactobacillus bulgaricus and Streptococcus thermophilus. The additions of fruits into milk may enhance the taste and the therapeutical values of milk products. However fruits also may change the fermentation behaviour. In this present study, the changes in physicochemical, the peptide concentration, total phenolics content and the antioxidant potential of yogurt upon the addition of Hylocereus polyrhizus and Hylocereus undatus (white and red dragon fruit) were investigated. Fruits enriched yogurt (10%, 20%, 30% w/w) were prepared and the pH, TTA, syneresis measurement, peptide concentration, total phenolics content and DPPH antioxidant inhibition percentage were determined. Milk fermentation rate was enhanced in red dragon fruit yogurt for all doses (-0.3606 - -0.4126 pH/h) while only white dragon fruit yogurt with 20% and 30% (w/w) composition showed increment in fermentation rate (-0.3471 - -0.3609 pH/h) compared to plain yogurt (-0.3369pH/h). All dragon fruit enriched yogurts generally showed lower pH readings (pH 3.95 - 4.03) compared to plain yogurt (pH 4.05). Both fruit yogurts showed a higher lactic acid percentage (1.14-1.23%) compared to plain yogurt (1.08%). Significantly higher syneresis percentage (57.19 - 70.32%) compared to plain yogurt (52.93%) were seen in all fruit enriched yogurts. The antioxidant activity of plain yogurt (19.16%) was enhanced by the presence of white and red dragon fruit (24.97- 45.74%). All fruit enriched yogurt showed an increment in total phenolic content (36.44 - 64.43mg/ml) compared to plain yogurt (20.25mg/ml). However, the addition of white and red dragon fruit did not enhance the proteolysis of milk during fermentation. Therefore, it could be concluded that the addition of white and red dragon fruit into yogurt enhanced the milk fermentation rate, lactic acid content, syneresis percentage, antioxidant activity, and total phenolics content in yogurt.

Keywords: Antioxidant activity, Hylocereus polyrhizus, Hylocereus undatus, yogurt

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Authors: Şt. Creangâ, V. Maciuc, A.V. Bâlteanu, S.S. Chelmu

Abstract:

The paper presents a part of the results obtained in a complex research project on Romanian Grey Steppe breed, owner of some remarkable qualities such as hardiness, longevity, adaptability, special resistance to ban weather and diseases and included in the genetic fund (G.D. no. 822/2008.) from Romania. Following the researches effectuated, we identified alleles of six loci, codifying the six types of major milk proteins: alpha-casein S1 (α S1-cz); beta-casein (β-cz); kappa-casein (K-cz); beta-lactoglobulin (β-lg); alpha-lactalbumin (α-la) and alpha-casein S2 (α S2-cz). In system αS1-cz allele αs1-Cn B has the highest frequency (0.700), in system β-cz allele β-Cn A2 ( 0.550 ), in system K-cz allele k-CnA2 ( 0.583 ) and heterozygote genotype AB ( 0.416 ) and BB (0.375), in system β-lg allele β-lgA1 has the highest frequency (0.542 ) and heterozygote genotype AB ( 0.500 ), in system α-la there is monomorphism for allele α-la B and similarly in system αS2-cz for allele αs2-Cn A. The milk analysis by the isoelectric focalization technique (I.E.F.) allowed the identification of a new allele for locus αS1-casein, for two of the individuals under analysis, namely allele called αS1-casein IRV. When experiments were repeated, we noticed that this is not a proteolysis band and it really was a new allele that has not been registered in the specialized literature so far. We identified two heterozygote individuals, carriers of this allele, namely: BIRV and CIRV. This discovery is extremely important if focus is laid on the national genetic patrimony.

Keywords: allele, breed, genetic preservation, lactoproteins, Romanian Grey Steppe

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Authors: Abtehal Y. Anaas, Mohd. Nazmi Bin Abd. Manap

Abstract:

Meat Tenderness is one of the most important factors affecting consumers' assessment of meat quality. Variation in meat tenderness is genetically controlled and varies among breeds, and it is also influenced by environmental factors that can affect its creation during rigor mortis and postmortem. The final postmortem meat tenderization relies on the extent of proteolysis of myofibrillar proteins caused by the endogenous activity of the proteolytic calpain system. This calpain system includes different calcium-dependent cysteine proteases, and an inhibitor, calpastatin. It is widely accepted that in farm animals including chickens, the μ-calpain gene (CAPN1) is a physiological candidate gene for meat tenderness. This study aimed to identify the association of single nucleotide polymorphism (SNP) markers in the CAPN1 gene with the tenderness of chicken breast meat from two Malaysian native and commercial broiler breed crosses. Ten, five months old native chickens and ten, 42 days commercial broilers were collected from the local market and breast muscles were removed two hours after slaughter, packed separately in plastic bags and kept at -20ºC for 24 h. The tenderness phenotype for all chickens’ breast meats was determined by Warner-Bratzler Shear Force (WBSF). Thawing and cooking losses were also measured in the same breast samples before using in WBSF determination. Polymerase chain reaction (PCR) was used to identify the previously reported C7198A and G9950A SNPs in the CAPN1 gene and assess their associations with meat tenderness in the two breeds. The broiler breast meat showed lower shear force values and lower thawing loss rates than the native chickens (p<0.05), whereas there were similar in the rates of cooking loss. The study confirms some previous results that the markers CAPN1 C7198A and G9950A were not significantly associated with the variation in meat tenderness in chickens. Therefore, further study is needed to confirm the functional molecular mechanism of these SNPs and evaluate their associations in different chicken populations.

Keywords: CAPNl, chicken, meat tenderness, meat quality, SNPs.

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