Oxidation of sarcoplasmic proteins during processing of Cantonese sausage in relation to their aggregation behaviour and in vitro digestibility

The physicochemical changes of sarcoplasmic proteins, especially oxidation behaviour, were measured to determine their mechanism of action on in vitro protein digestibility during Cantonese sausage processing. The results indicated that carbonyl level increased (p<0.05) during the process. The fluorescence loss of tryptophan residues was a direct consequence of the oxidative degradation. All the parameters of protein aggregation were highly (p<0.05) correlated with carbonyl level and protein surface hydrophobicity (H(0)), indicating that protein oxidation and thermal denaturation could induce protein aggregation, leading to secondary structural changes. The analysis of in vitro digestibility showed no correlation between pepsin activity and protein oxidation, due to the biphasic response of sarcoplasmic proteins toward proteolysis. However, a highly significant (p<0.05) correlation was observed with trypsin and α-chymotrypsin activity, indicating that protein oxidation induced the changes in H(0), protein aggregation and secondary structure, which further influenced in vitro digestibility.     

Physicochemical changes of myofibrillar proteins during processing of Cantonese sausage in relation to their aggregation behaviour and in vitro digestibility

The physicochemical changes of myofibrillar proteins, especially oxidation behaviour, were measured to determine their mechanism of action on in vitro protein digestibility during Cantonese sausage processing. The results indicated that the carbonyl level significantly increased (p < 0.05) during the process. The SH group level decreased, while S–S group level increased gradually. Protein aggregation was induced by oxidation and heat treatment. Result from Fourier transform infrared (FTIR) spectroscopy confirmed protein aggregation occurred. The analysis of in vitro digestibility showed a highly significant (p < 0.05) correlation between pepsin activity and carbonyl group formation, S–S group level, protein surface hydrophobicity, D_4,3. A negative and highly significant correlation between trypsin, α-chymotrypsin activity and carbonyl group formation was measured, while no significant correlation with S–S groups, protein surface hydrophobicity, D_4,3 was observed. It indicated that not only protein oxidation and aggregation but also degradation by pepsin would influence proteolysis with trypsin and α-chymotrypsin.     

Changes in lipid composition,fatty acid profile and lipid oxidative stability during Cantonese sausage processing

Lipid composition, fatty acid profile and lipid oxidative stability were evaluated during Cantonese sausage processing. Free fatty acids increased with concomitant decrease of phospholipids. Total content of free fatty acids at 72 h in muscle and adipose tissue was 7.341 mg/g and 3.067 mg/g, respectively. Total amount of saturated, monounsaturated and polyunsaturated fatty acids (SFA, MUFA, and PUFA) in neutral lipid exhibited a little change during processing, while the proportion of PUFA significantly decreased in the PL fraction. The main triacylglycerols were POO + SLO + OOO, PSO (P = palmitic acid, O = oleic acid, L = linoleic acid, S = stearic acid), and a preferential hydrolysis of palmitic, oleic and linoleic acid was observed. Phosphatidylcholines (PC) and phosphatidylethanolamines (PE) were the main components of phospholipids and PE exhibited the most significant degradation during processing. Thiobarbituric acid values (TBARS) increased while peroxide values and hexanal contents varied during processing.     

Structural characteristics of peptides extracted from Cantonese sausage during drying and their antioxidant activities

Two peptide fractions (P1 and P2) were isolated from Cantonese sausages at different drying periods by ultrafiltration. P1 possessed a stronger 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity in the first 18 h of drying and a weaker activity during the rest period, comparing with P2. The analysis of amino acid composition indicated that histidine was the major amino acid in both peptide fractions, which content was changed during the process. In addition, Glu, Gly, Arg were important constituent amino acids in both peptide fractions. A significant (P < 0.05) decrease of >10 kDa peptide fraction and increases of 2–3 and <2 kDa peptide fractions were detected when comparing with peptides at 0 h. However, no significant difference was found for all the peptide fractions at different drying periods, except for 2–3 kDa peptides. A significant (P < 0.05) correlationship was found between lipid oxidation and antioxidant activities.

Industrial relevance

Cantonese sausage has gained much popularity and acceptance in China and many other countries. In this work, two peptide fractions were isolated from Cantonese sausage. A good antioxidant activity was observed for each peptide fraction. Endogenous peptides resulting from proteolysis offer a promising approach to improve lipid stability for meat industry. It is helpful to retard lipid oxidation in order to improve its quality.     

Chemical oxidation decreases proteolytic susceptibility of skeletal muscle myofibrillar proteins

The objective of this study was to investigate the effect of chemical oxidation on proteolysis susceptibility of myofibrillar proteins. Myofibrils were prepared from pig M. longissimus dorsi and oxidised by a hydroxyl radical generating system. Protein oxidation level was measured by the carbonyl content, free thiol group content and bityrosine formation. Oxidised or non-oxidised myofibrillar proteins were exposed to papain and proteolysis was estimated by fluorescence using fluorescamine. Oxidation of myofibrillar proteins was dependent upon the oxidising agent concentration. Disulfide bridge and bityrosine formation indicated that oxidation by OH° can induce protein polymerization. Electrophoretic study showed that myosin was the protein most sensitive to oxidation. Results showed a direct and quantitative relationship between protein damages by hydroxyl radical and decreased proteolytic susceptibility. Electrophoretic observations suggest that polymerization and aggregation may explain in part decreased susceptibility of myofibrillar proteins to proteolysis.     

Volatile compounds of Cantonese sausage released at different stages of processing and storage

The volatile compounds of Cantonese sausage at different stages of processing and storage were analysed by gas chromatography/mass spectrometry (GC/MS) with solid-phase microextraction (SPME). One hundred and four volatile compounds were identified. Esters and alcohols were the most important chemicals in all the samples, accounting for 16.94–50.12% and 30.01–65.54% of the total area, respectively. Ethanol and its alcohol esters were the major volatile compounds of Cantonese sausage, which suggested that the alcohol added to sausage at the preparation stage was the most important factor for the characteristic flavour of Cantonese sausage. Aldehydes (especially hexanal) contributed between 3.33% and 17.42% to the total areas. The presence of carboxylic acids in esters indicated that lipid oxidation played a key role on the flavour formation of Cantonese sausage. Amino acid catabolism and microbial activity also played an active role in the formation of volatile compounds.     

广式腊肠加工过程中肠球菌变化规律及其分离鉴定

本文对广式腊肠烘烤加工过程中肠球菌的变化规律进行了研究,结果发现:肠球菌在烘烤0-18 h时数量增加,烘烤18,,-54h数量下降,烘烤54h后数量缓慢提高,至烘烤结束时肠球菌数量为2.74logcfu/g,占乳酸菌总数的0.04%,为次要茵群.分离得到的两株肠球菌AD4和AD8经鉴定为屎肠球菌.AD4和AD8能够在50℃生长以及耐受6.5%NaCl,因此能够适应广式腊肠的环境;AD4和AD8均不具有明胶酶活性,但都具有溶血性,表明广式腊肠中的肠球菌具有某些毒力因子.     

中式香肠风干过程中蛋白氧化对蛋白聚集、水解性及溶解性的影响

从中式香肠中提取肌浆蛋白和肌原纤维蛋白,并测定其羰基值、巯基值和蛋白浊度,以及蛋白质降解情况和溶解性,确定蛋白氧化对蛋白聚集性、水解性和溶解性的影响。研究结果表明:蛋白羰基含量都显著增长,巯基含量显著下降。蛋白氧化导致蛋白溶液浊度上升,蛋白表面疏水性增加,以及蛋白发生不同程度的降解。蛋白溶解性实验表明氢键、疏水作用力、二硫键和离子键是形成香肠蛋白三维网状结构的主要作用力。     

Effect of starter culture on proteolytic changes during processing of fermented beef sausages

Fermented beef sausages inoculated with four different starter cultures (Pediococcus acidilactici,Lactobacillus curvatus, Lactobacillus sake, or Streptomyces griseus) were evaluated for proteolysis during process stages (prefermentation, fermentation, drying and heating). Increases (p ? 0.05) in the nonprotein nitrogen (NPN) fraction were found at sequential stages of processing, while starter cultures had no major effects on NPN content. Concentrations of most free amino acids increased (p ? 0.05) during fermentation and drying, and culture effects were found for differences among concentrations of some individual free amino acids. From SDS–PAGE analysis of sarcoplasmic and myofibrillar protein fractions after fermentation and drying, myosin heavy and light chains, actin and troponin were degraded during processing. However, starter culture effects were absent from SDS–PAGE protein patterns.     

Effect of sage (Salvia officinalis) on the oxidative stability of Chinese-style sausage during refrigerated storage

The objective of this study was to assess the effect of sage, at levels of 0.05%, 0.1% and 0.15% (w/w), on the oxidative stability of Chinese-style sausage stored at 4 °C for 21 days. The results showed that inclusion of sage in sausages resulted in lower L* values (P < 0.05) and higher a* values (P < 0.05) compared to the control. During refrigerated storage, sausages containing sage showed significantly retarded increases in TBARS values, and in the formation of protein carbonyls (P < 0.05), but showed accelerated losses of thiol groups (P < 0.05). Addition of sage to the sausages at levels of 0.1% and 0.15% reduced textural deterioration during refrigerated storage (P < 0.05). Sage used in this study had no negative effects on the sensory properties of sausages.     

Changes in lipid composition and fatty acid profile of Nham,a Thai fermented pork sausage,during fermentation

Changes in lipid composition and fatty acid profile of Nham during fermentation were investigated. Total lipids of Nham were in the range 2–3%. The extracted lipid of initial Nham mix consisted mainly of triglycerides (TG), accounting for more than 75% of the total lipid, followed by phospholipids (PL) and a trace amount of diglycerides (DG) and free fatty acid (FFA). During fermentation, TG, DG and PL decreased with a concomitant increase in FFA, indicating lipolysis of Nham lipids during fermentation. Changes in fatty acids of the total lipids, non-polar and polar lipid fractions were observed during fermentation. In both total and non-polar lipid fractions, the major fatty acids found in a descending order were oleic (C18:1), linoleic (C18:2) and palmitic (C16:0) acids, which together accounted for 90% of the total fatty acids. Increases in fatty acid contents in both total and non-polar lipid fractions, were observed with a corresponding decrease in the quantity of fatty acids of phospholipids. As the fermentation proceeded, peroxide value generally increased while TBARS values decreased. Overall, lipid oxidation in Nham occurred during fermentation but did not cause the objectionable odour and taste in any Nham tested.     

The amino acid composition,solubility and emulsifying properties of sweet potato protein

A protein was purified from the high-protein type sweet potato variety 55-2 available in China. The amino acid composition, solubility and emulsifying properties of the sweet potato protein (SPP) were studied. The SPP was rich in aspartic acid (18.5%) and glutamic acid (9.30%) while essential acid amino acids made up approximately 40.7% of the SPP. The SPP was highly soluble in distilled water over a wide range of pH. However, solubility of the SPP in 1.0 M NaCl and 1.0 M CaCl₂ solutions was low especially at pH below the pI of the SPP. The SPP in CaCl₂ demonstrated emulsifying activity index (EAI) and emulsion stability index (ESI) many folds higher than those in distilled water and NaCl solution (P < 0.05).     

Effect of Flavourzyme on proteolysis,antioxidant capacity and sensory attributes of Chinese sausage

The objective of this study was to investigate the effect of Flavourzyme, at levels of 0 (control) 4, 8, 12, 16 and 20 LAPU/kg raw meat, on the proteolysis, antioxidant capacity and sensory attributes of Chinese sausage made at 50 °C for 48 h. Results showed that Flavourzyme addition in Chinese sausage accelerated protein degradation, which was reflected by the increase of non-protein nitrogen and appearance of new protein bands in both water-soluble and salt-soluble proteins. By adding Flavourzyme, texture profile analysis (TPA) parameters decreased significantly, and aroma, taste and texture scores were enhanced, respectively. The best sensory attributes were obtained at 8 and 12 LAPU/kg Flavourzyme dose. Besides, Flavourzyme addition enhanced antioxidant capacity, lowered water activity and TBARS values of Chinese sausage. Therefore, moderate Flavourzyme addition is a novel method with great potential to improve eating properties and storage stability of Chinese sausage.     

发酵干香肠生产过程中的理化变化研究

对发酵干香肠生产过程中的理化变化进行了跟踪测定,结果表明,pH值、水分活度、水分含量、蛋白质水解指数、游离氨基酸、酸价和过氧化值等理化因子皆发生显著变化。     

Effects of skipjack roe protein hydrolysate on properties and oxidative stability of fish emulsion sausage

Effects of skipjack roe protein hydrolysate (SRPH) at various levels (0–3 g/100 g) on properties and oxidative stability of emulsion sausage from broadhead catfish (Clarias macrocephalus) fortified with skipjack tuna roe lipids were investigated. The addition of SRPH increased hardness, cohesiveness and resilience of sausage (p < 0.05). Finer fat globules were visualised in the sample added with SRPH at higher amounts. Nevertheless, the incorporation of SRPH at all levels had no impact on likeness of sausages. SRPH was shown to retard lipid oxidation of sausage during extended storage of 12 days as evidenced by the lower peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS), in comparison with the control. After 12 days, the sausage with 3 g/100 g SRPH had the retained docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), accounting more than 80%. Addition of SRPH had no effect on the organoleptic properties but could prevent the development of rancidity. Nevertheless, it showed no pronounced impact on microbial growth. SRPH could therefore be used as a natural antioxidative emulsifier in cooked fish emulsion sausage.     

Effects of composition and processing variables on the oxidative stability of protein-based and oil-in-water food emulsions

Because many common foods are emulsions (mayonnaise, coffee creamers, salad dressing, etc.), a better understanding of lipid oxidation mechanisms in these systems is crucial for the formulation, production, and storage of the relevant consumer products. A research body has focused on the microstructural and oxidative stability of protein-stabilized oil-in-water emulsions that are structurally similar to innovative products that have been recently developed by the food industry (e.g., non-dairy creams, vegetable fat spreads, etc.) This review presents recent findings about the factors that determine the development of lipid oxidation in emulsions where proteins constitute the stabilizing interface. Emphasis is given to “endogenous” factors, such as those of compositional (e.g., protein/lipid phases, pH, presence of transition metals) or processing (e.g., temperature, droplet size) nature. Improved knowledge of the conditions that favor the oxidative protection of protein in emulsions can lead to their optimized use as food ingredients and thereby improve the organoleptic and nutritional value of the related products.     

Effect of processing on proteolysis and biogenic amines formation in a Portuguese traditional dry-fermented ripened sausage “Chouriço Grosso de Estremoz e Borba PGI”

The influence of alternative drying environmental conditions on the proteolysis of a traditional Portuguese fermented sausage was evaluated, in relation to different ripening periods. Traditional sausages (batch T) had lower pH than counterparts (batch M), with differences (P < 0.05) focused at the fermentation stage. A remarkable accumulation of free amino acids (FAA) was detected in both batches along the ripening process, with batch T having higher mean levels than batch M (1795.2 mg 100 g⁻¹ DM vs. 1742 mg 100 g⁻¹ DM in S7, respectively), but with differences being significant for long ripened products. In both batches, glutamic acid became the most concentrated FAA in end products currently consumed (101.6 mg 100 g⁻¹ DM and 111.0 mg 100 g⁻¹ DM – S6; 233.8 mg 100 g⁻¹ DM and 220.9 mg 100 g⁻¹ DM – S7 from batches T and M, respectively) followed by leucine > alanine > taurine > serine > valine and taurine > alanine > leucine > serine > valine sequences in the former product from batches T and M, respectively, and, coincidently, the same sequence for both batches in the later (serine > leucine > alanine > proline > valine). Such effect on FAA concentrations led to a distinct (P < 0.05) expression of sweet, bitter, acidic and aged sensorial attributes between batches, in S8 and S9 products.BA typical quantitative sequences varied between batches according to the ripening stage, with differences in S6 and S7 end products also reflecting the distinct microbial development rates and profiles observed. Overall, the total BA mean concentration was higher (P < 0.05) in products from batch T.     

Effect of processing methods and starter culture (Staphylococcus xylosus and Pediococcus pentosaceus) on proteolytic changes in Turkish sausages (sucuk) during ripening and storage

Proteolytic changes in Turkish sausages (sucuk) produced by two methods (heat processing and traditional) were determined during processing and storage for 90 days. The sausages were produced with or without starter culture in both methods. A mixture of Staphylococcus xylosus and Pediococcus pentosaceus was used as starter culture for their acidic and proteolytic characteristics.The major changes in proteolytic characteristics of sucuk took place during the fermentation stage, with an increase in non-protein nitrogen (NPN) and a decrease in protein solubility. Proteolytic activity was observed in both starter-inoculated and non-inoculated (control) sausages during processing. Moreover, a slight increase in proteolytic activity was detected during storage in both starter-inoculated and control traditional sausages, and also in heat-processed sausages due to some heat-resistant proteolytic enzymes. Protein solubility was significantly affected by processing time and heat treatment. Sarcoplasmic and myofibrillar proteins were also affected by starter addition, fermentation, drying and heat processing. During fermentation, starter-inoculated and control sausages showed intense proteolysis in both the traditional and heat processing methods. After heating, intensive degradation of both sarcoplasmic and myofibrillar proteins due to denaturation was observed in heat-processed samples.     

Comparative studies on lipid oxidation of organic model sausage without nitrite produced with the addition of native or autoclaved mustard seed and acid whey

The objective of this work was to evaluate the influence of the addition of native and autoclaved mustard seed (AMS) with combination of acid whey (AW) on the stability of organic model sausages during 30 days of vacuum storage by measuring primary and secondary products of lipid oxidation, the changes in the fatty acid composition, oxidation–reduction potential and antioxidant capacity. Briefly, the addition of AW (5%) with combination of AMS (1%) significantly increased the capacity of sausages to capture the radical cations 2,2‐azinobis(3‐ethyl‐benzothiazoline)‐6‐sulphonate at 1 day of storage which suggests that autoclaved mustard possessed significantly higher amount of phenolic acids compared with native mustard. The salted samples with mustard seed addition characterised by lower oxidation–reduction potential values (264.5–302.1 mV) during the whole storage period compared with control‐cured sample (307.3–330.5 mV). Results of conjugated dienes (CD) measurements indicated that salted meat product samples with mustard seed addition were characterised by significantly lower CD concentration (1.12–1.90 μmol mg^?1 meat product) compared with control‐cured sample (1.86–2.55 μmol mg^?1 meat product). The AW and mustard seed added to uncured sausage were able to protect polyunsaturated fatty acids against the oxidation comparable to nitrite.     

Effect of Maillard reaction products derived from the hydrolysate of mechanically deboned chicken residue on the antioxidant,textural and sensory properties of Cantonese sausages

Protein hydrolysates as precursors of Maillard reaction were obtained via enzymatic hydrolysis of mechanically deboned chicken residue (MDCR). The Maillard reaction products (MRPs) were prepared at 90 (M1), 100 (M2), 110 (M3) and 120 °C (M4), respectively. MRPs possessed a strong reducing power and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. According to the evolution of total free fatty acids and peroxide value of Cantonese sausage with MRPs during storage, M1 and M3 had a potent antioxidant activity (P < 0.05) due to their antioxidant abilities and inhibitory action against lipolytic enzymes. Cantonese sausages treated with M1 and M2 showed good textural and sensory properties. However, M3 and M4 had a negative (P < 0.05) effect on the flavour and texture of Cantonese sausages compared to control. The results suggested that M1 was very potential to be used to improve their antioxidant, textural and sensory quality.