Quantitative aspects of two methods to dissolve collagen-free muscle proteins from acetone dry powders of Guelders ring sausage

The purpose of this study was to find experimental conditions for the complete solubility of collagen-free muscle proteins (CFMP) using acetone powder of Guelders ring sausage. Preliminary experiments were carried out to choose the best procedure for preparing the acetone dry powder. Two different methods of acetone extraction of minced sausage were compared. The acetone dry mass (ADM) method using continuous extraction in a Soxhlet [2] apparatus gave better results than the acetone powder (ACP) method, which used a blender [1]. The ADM method was used for further investigations. ADM was extracted with two types of sodium dodecyl sulphate (SDS), containing solvents A and B. Solvent A contains a Tris-boric acid buffer (pH 8.2) with 1.5% (m/v) SDS and 0.05% (m/v) dithioerythreitol [3]. Solvent B is a borate-chloric acid buffer (pH 9.0) with 2.0% (m/v) SDS and 1.0% (m/v) mercapto-ethanol [2]. Both solvents showed a linear relationship between the quantities of CFMP in ADM and the dissolved CFMP. The linear relationships were found between quantities of 10.0 and 30.0 mg (solution A) and of 5.0 and 30.0 mg ADM (solution B) per ml solvent. The solubility of CFMP was better in solvent B than in solution A. Completely dissolved CFMP from ADM was only obtained in the case of 5.0 mg ADM in 1.0 ml solution B. These conditions will be used in liquid chromatography experiments, the results of which will be reported later.     

Actin, a possible quantitative indicator for the quality of meat products. II. Separation and determination of actin from a Guelders ring sausage

Quality regulations of the Guelders ring sausage are applied in the Netherlands. One of the quality parameters is the content of CFMP (collagen-free muscle protein) in the product. The purpose of this research is to substitute the usual indirect method by a direct analytical method for CFMP. The proposed direct method is composed of separation and determination of actin. Actin was well separated from the sausage product by SDS-gel-filtration chromatography, which was checked by SDS-polyacrylamide-gel electrophoresis. Actin was determined by its 3-methylhistidine content, but this result was smaller than expected. It was caused by the presence of salt during the 3-methylhistidine analysis. Finally, a method for the determination of actin by 3-methylhistidine was developed for the direct procedure. The relations of 3 MH (3-methylhistidine) with respective CFMP and MP (muscle protein) are formulated. Both formulae give a reasonably good estimation of 3 MH, CFMP or MP, one of these parameters of the Guelders ring sausage being known.     

Esterase activity and zymograms of acetone powders from stored Golden Delicious and Cox's Orange Pippin apples

Summary Acetone powders derived from Golden Delicious apples stored under controlled atmosphere (CA) at 3–4 °C for a total period of 236 days and Cox's Orange Pippin (Cox) apples stored in air at 17 °C for a total period of 70 days were used as sources for estimation of esterase activity and zymogram patterns. For Golden Delicious apples, esterase activity remained constant until the 152nd day of storage, after which it decreased. For Cox apples, it remained constant for 39 days then increased. In both varieties, although stored unter extremely different conditions, the zymograms remained constant. Characterization of esterase by incubating with di-isopropyl-fluorophosphate (DFP) (10^–4 M) andp-chloromercuribenzoate (PCMB) (10^–3 M) for 24 h, indicated that esterase systems in Golden Delicious apples were more susceptible to inhibition by DFP than those of Cox apples. Conversely PCMB had a greater effect on Cox esterase systems than on Golden Delicious.

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Esterase-Aktivität und Zymogramme von Acetonpulvern aus Lageräpfeln der Sorten Golden Delicious und Cox's Orange Pippin

Zusammenfassung Acetonpulver von Golden Delicious-Äpfeln, die in kontrollierter Atmosphäre bei 3–4 °C 236 Tage gelagert wurden, und von Cox's Orange Pippin (Cox)-Äpfeln, die in Luft bei 17°C 70 Tage gelagert wurden, dienten zur Bestimmung der Esterase-Aktivität und für die Zymogramme.Die Golden Delicious-Esterase-aktivität blieb bis zum 152. Tag der Lagerung konstant und nahm dann ab. Die Cox-Esterase-aktivität blieb 39 Tage konstant und stieg danach an. Die Zymogramme beider Äpfelsorten wiesen während der Lagerung keine Veränderungen auf, ungeachtet der wesentlich ungleichen Lagerungsbedingungen.Eine Incubation mit Di-isopropyl-fluorophosphat (DFP, 10^–4 mol/1) und mit p-Chlormercuribenzoat (PCMB, 10^–3 mol/1) zeigte, daß Golden Delicious-Esterase gegenüber DFP-Hemmung empfindlicher ist als Cox. Hinsichtlich der PCMB-Hemmung zeigte sich gerade das Umgekehrte.

     

Composition, solubility and gel properties of salt soluble proteins from two bovine muscle types

The composition, pH solubility profile and thermal gelation behavior of two bovine muscles, vastus intermedius (VI, predominately red fibers) and semimembranosus (SM, predominantly white fibers) were compared. VI had a higher fat content and pH and lower protein content than SM. Between pH 5.2 and 5.8, the salt soluble proteins (SSP) from SM were more soluble than those from VI at the same pH, whereas solubilities above pH 6.0 were similar. Properties of SSP gels were measured at pH 5.5 and 6.1, the ultimate pH for SM and VI, respectively. Water lost from the VI gels due to syneresis was about 3 times greater than that lost from SM gels. VI gels prepared at pH 5.5 were firmer (p<0.05) than at pH 6.1, whereas deformability of SM gels at pH 6.1 were greater (p<0.05) than at pH 5.5. No differences (p>0.05) were observed between the firmness or deformability of VI or SM gels when compared at the same pH. Results suggest that ultimate muscle pH and fiber type do influence the properties of bovine SSP gels, although the effect is not as great as that previously reported for poultry muscle proteins.     

两种大豆蛋白分级方法的比较研究

以低温脱脂豆粉为原料,比较大豆蛋白经Nagano法和Samoto法分级所得组分在蛋白质含量、得率、SDS-PAGE、热力学性质和溶解度等方面的异同。研究表明,两种方法所得11S和7S组分的蛋白质含量均高于IM和LP组分,Nagano三种组分的蛋白质含量均高于Samoto相应组分。Samoto的11S和7S组分以及总蛋白得率较高。两种方法所得11S组分的纯度相近,7S组分中Nagano的纯度明显低于Samoto。IM和LP组分中11S亚基均多于7S亚基,LP组分中储藏蛋白所占比例低于IM。两种11S组分中的7S球蛋白几乎完全变性,Samoto的LP组分中蛋白变性程度较Nagano的IM高。pH7.0条件下,LP组分的溶解性最差,其它组分的溶解度相对较高。     

不同解冻方式对鲣鱼鱼肉蛋白及组胺变化的影响

以冷冻鲣鱼为研究对象,探究不同解冻方式(自然空气解冻、静水解冻、流水解冻、冷藏库解冻)对其高铁肌红蛋白(metmyoglobin,met Mb)、可溶性肌原纤维蛋白(soluble myofibrillar proteins,SMP)、可溶性肌浆蛋白(soluble sarcoplasmic proteins,SSP)、Ca~(2+)-ATPase活性、活性巯基(reactive sulfhydryl,A-SH)及组胺含量的影响,并结合解冻汁液流失率、色泽、质构评价。结果表明,解冻汁液流失率和咀嚼性与肌原纤维蛋白变化指标(SMP含量、Ca~(2+)-ATPase活性、A-SH含量)之间,Ca~(2+)-ATPase活性与A-SH含量之间分别极显著相关(P0.01)。相比其他3种解冻方式,冷藏库解冻显著(P0.05)的抑制组胺的生成及氧合肌红蛋白的氧化,保持色泽。此外,冷藏库解冻较好地保持了肌原纤维蛋白的结构和功能特性,汁液流失率最低,质构较好。因此,冷藏库解冻适合作为鲣鱼罐头生产的解冻方式。     

Quantitative structure-activity relationship modelling of ACE-inhibitory peptides derived from milk proteins

The potential of Lactobacillus plantarum, Pediococcus acidilactici, Pediococcus pentocaceus, Lactobacillus cellobiosus, different mixtures of these lactic acid bacteria and backslop starter cultures to acidify and form flavour compounds in uji was investigated. The bacteria chosen are the most prevalent species in fermented uji. Flavour compounds were analysed using GC-MS and GC-FID with HP5 non-polar column and DB-Wax polar columns respectively. Use of pure single or mixed cultures did not improve the flavour profile of fermented uji. On the basis of peak areas of unfermented and fermented uji aromagrams, pentanal, hexanal and hexadecanoic, 9,12-octadecadienoic, oleic and octadecanoic acids were found to be native to the flours, while 3-methyl-1-butanol, octanoate, nonanoate, hexadecanoate, linoleate, oleate and hexanoic, heptanoic, octanoic and nonanoic acids were synthesised during submerged culture fermentation. Ethanol, 1-pentanol, 1-hexanol, lactic acid and ethylacetate were synthesised prior to fermentation and synthesis of these compounds continued during fermentation.     

Migration kinetics of mineral oil hydrocarbons from recycled paperboard to dry food: monitoring of two real cases

Mineral oil hydrocarbons present in printing inks and recycled paper migrate from paper-based food packaging to foods primarily through the gas phase. Migration from two commercial products packed in recycled paperboard, i.e. muesli and egg pasta, was monitored up to the end of their shelf life (1 year) to study the influence of time, storage conditions, food packaging structure and temperature. Mineral oil saturated and aromatic hydrocarbons (MOSH and MOAH, respectively), and diisopropyl naphthalenes (DIPN) were monitored using online HPLC-GC/FID. Storage conditions were: free standing, shelved, and packed in transport boxes of corrugated board, to represent domestic, supermarket and warehouse storage, respectively. Migration to food whose packs were kept in transport boxes was the highest, especially after prolonged storage, followed by shelved and free-standing packs. Tested temperatures were representative of refrigeration, room temperature, storage in summer months and accelerated migration testing. Migration was strongly influenced by temperature: for egg pasta directly packed in paperboard, around 30 mg kg^?1 of MOSH migrated in 8 months at 20°C, but in only 1week at 40°C. Muesli was contained into an internal polyethylene bag, which firstly adsorbed hydrocarbons and later released them partly towards the food. Differently, the external polypropylene bag, containing pasta and recycled paper tray, strongly limited the migration towards the atmosphere and gave rise to the highest level of food contamination. Tests at increased temperatures not only accelerated migration, but also widened the migration of hydrocarbons to higher molecular masses, highlighting thus a difficult interpretation of data from accelerated simulation.     

Optimisation of the addition of carrot dietary fibre to a dry fermented sausage (sobrassada) using artificial neural networks

An optimisation problem was formulated to maximise the amount of carrot dietary fibre (CDF) in a dry fermented sausage, while maintaining product quality, by using 0–12% CDF as the decision variable, and limiting values of several physico-chemical and textural parameters (moisture content, water activity, pH, colour, non-protein nitrogen, free fatty acid, compression work and hardness) as constraints.     

Comparison of immunohistochemical,histochemical and immunochemical methods for the detection of wheat protein allergens in meat samples and cooked,dry, raw and fermented sausage samples

Nowadays is it a common practice to add vegetable protein in the production of meat products. Because of the possible substitution of high-quality raw meat with vegetable protein without the labelling the product package and because of the allergenic potential of many vegetable proteins, it is important to develop accurate methods for its detection. The objective of the study was to compare histochemical, immunochemical (ELISA, ALERT gliadin screening test) and immunohistochemical methods for the detection of wheat protein in meat samples and sausages. Histochemical methods were useful for the detection of flour in meat samples, but the immunohistochemical method was better for the detection of wheat protein. ALERT gliadin screening test detected gliadin from 10?mg?kg^?1, while an immunohistochemical method detected wheat protein concentrations from 1?g?kg^?1 and an ELISA method detected wheat protein concentrations from 4?g?kg^?1. ALERT gliadin screening test showed results within 1 day, whilst an ELISA detection method took 2 days, and an immunohistochemical procedure took 5 days at the soonest, all including sample preparation. This study also focused on optimisation of an immunohistochemical method for samples of cooked sausage. In addition, three samples were sufficient for wheat protein detection at a concentration of 1?g?kg^?1 (and greater) with a confidence level greater than 95%.     

Effect of brine salting at different pHs on the functional properties of cod muscle proteins after subsequent dry salting

Fillets of Atlantic cod (Gadus morhua) were wet-salted in brines of pH 6.5 and 8.5 containing different combinations of NaCl, KCl, MgCl₂ and CaCl₂, then dry-salted in NaCl. Proximate analyses, functional properties (water holding capacity and protein solubility) and hardness were determined in the dry-salted cod. The compositions of the protein fractions soluble in water and in 0.86 M sodium chloride were determined by SDS–PAGE. The composition and pH of the brines slightly affected the protein composition of the major extract constituents and the functional properties of the muscle after dry-salting. Brining at alkaline pH produced a larger variety of water-soluble proteins, particularly actin, than at pH 6.5. Furthermore, the compositions of the protein fractions extracted with 0.86 M NaCl were very similar for both pHs, irrespective of the composition of the brine; in this case, myosin heavy chains were absent in both extracts due to aggregation caused by a massive uptake of salt by the muscle.     

Production of a dry sausage from African catfish (Clarias gariepinus, Burchell, 1822): microbial, chemical and sensory evaluations

Production of a dry sausage from African catfish and determination of its microbial, chemical and sensory properties during a 70‐day storage at both 4 and 22 °C were prompted. pH of the samples at 4 and 22 °C did not significantly change during the storage (P > 0.05). Moisture content of the samples was 74%, and reduced to 45% at 4 °C and to 22% at 22 °C. Protein content of the samples was 20.71%, and increased to 42.5% at 4 °C and to 57.99% at 22 °C. Total lipid content was 4.5%, and increased to 10.98% at 4 °C and to 15.68% at 22 °C (P < 0.05). Microbial analyses showed that there was a significant reduction in total aerobic mesophilic and psychrotrophilic bacteria, total mould and yeast, total lactic acid bacteria, total Enterobacteriaceae and Staphylococcus aureus counts at both 4 and 22 °C (P < 0.05). Samples stored at 4 °C had significantly higher sensory ratings than that of the samples stored at 22 °C (P < 0.05).     

Application of high hydrostatic pressure to eliminate Listeria monocytogenes from fresh pork sausage.

Ground pork patties were inoculated separately with 10(9) CFU/g each of three strains of Listeria monocytogenes obtained from the National Animal Disease Center (NADC). Inoculated patties were packaged under vacuum and treated at 414 megapascals (60,000 lb/in2) for up to 60 min by high hydrostatic pressure (HHP). Survivors were determined by surface plating onto modified Oxford agar and trypticase soy agar with yeast extract, as well as by the most probable number method using Listeria enrichment broth. Average D values ranged from 1.89 to 4.17 min, depending on the strain, with the most virulent strain (reported by the NADC) having the highest D value. We tested the usefulness of applying a mild heat treatment at 50 degrees C, simultaneously with HHP, to lower these values. Average D values ranged from 0.37 to 0.63 min, depending on the strain. Thus, a 10-log10 reduction could be achieved even in the most pressure-resistant strain of L. monocytogenes by a 6-min application of heat and HHP. Shelf life studies were also conducted, with spoilage levels reached after 5 days of storage at 4 degrees C for controls versus 28 days for treated samples. Sensory evaluation of uninoculated grilled patties showed that panelists could not distinguish between those treated by heat and HHP and untreated controls (P<0.05). Thus, treatment by HHP in combination with mild heating can be used successfully to produce safer, longer-lasting fresh pork without affecting quality.     

Application of high pressure processing to reduce verotoxigenic E. coli in two types of dry-fermented sausage

The effect of high pressure processing (HPP) on the survival of verotoxigenic Escherichia coli (VTEC) in two types of Norwegian type dry-fermented sausages was studied. Two different types of recipes for each sausage type were produced. The sausage batter was inoculated with 6.8 log₁₀ CFU/g of VTEC O103:H25. After fermentation, drying and maturation, slices of finished sausages were vacuum packed and subjected to two treatment regimes of HPP. One group was treated at 600 MPa for 10 min and another at three cycles of 600 MPa for 200 s per cycle. A generalized linear model split by recipe type showed that these two HPP treatments on standard recipe sausages reduced E. coli by 2.9 log₁₀ CFU/g and 3.3 log₁₀ CFU/g, respectively. In the recipe with higher levels of dextrose, sodium chloride and sodium nitrite E. coli reduction was 2.7 log₁₀ CFU/g in both treatments. The data show that HPP has a potential to make the sausages safer and also that the effect depends somewhat on recipe.     

芦笋老茎中皂苷两种提取工艺的比较

研究比较浸提法和超声法中温度、料液比、乙醇浓度、提取时间对芦笋老茎中皂苷提取量的影响,并进一步采用正交实验获得两种方法的最佳提取条件。结果表明,超声法最佳提取条件为温度50℃,料液比1∶35,乙醇浓度60%,提取时间50min,其最高提取量为5.01%,比浸提法最高提取量提高了29.3%,同时超声法提取时间显著低于浸提法的提取时间。因此,超声法适用于芦笋老茎中皂苷的提取。     

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.     

Comparison of two methods to assess the intake of flavouring substances

It is important to assess the intake of flavouring substances in order to be confident that exposure to the substance from its intended use presents no significant risk. A number of methods exist to estimate intake of food ingredients. Two such methods, one using a detailed dietary analysis based on food consumption and composition and one using 10 times the annual volume of use on a per capita basis (per capita x 10), were compared for their precision and practicality in assessing the intake of 10 flavouring substances. The detailed dietary analysis method of determining exposure resulted in good estimates of the distribution of intakes across the population, as well as patterns of intake of individuals. This method is both expensive and labour intensive. The per capita x 10 method yields results that, compared with those obtained by detailed dietary analysis, tend consistently to overstate exposure. Thus, this method is a conservative and practical approach to assessing exposure to flavouring substances and other food ingredients.     

Populations of Vibrio parahaemolyticus in retail oysters from Florida using two methods

Vibrio parahaemolyticus is a naturally occurring estuarine bacterium that is often associated with gastroenteritis in humans following consumption of raw molluscan shellfish. A number of studies have investigated the environmental distribution of V. parahaemolyticus, but little is known about the levels of this organism during distribution of oysters or at the point of consumption. Duplicate samples of shellstock oysters were collected monthly (September 1997 to May 1998) from the same four restaurants and three wholesale seafood markets in the Gainesville, Fla. area and analyzed for total V. parahaemolyticus densities using two methods: a standard MPN method (BAM-MPN) and a new direct plating procedure (direct-VPAP). Both methods employed an alkaline phosphatase-labeled DNA probe (VPAP) targeting the species-specific thermolabile hemolysin (tlh) gene to confirm suspect colonies as V. parahaemolyticus. The highest monthly geometric mean V. parahaemolyticus density was observed in October of 1997 (approximately 3,000/g) with similarly high values during September and November of 1997. From December 1997 to May 1998 mean densities were generally less than 100/g, falling to approximately 10/g in February and March. A strong correlation (r = 0.78) between the direct-VPAP and BAM-MPN methods for determining V. parahaemolyticus densities in market-level oysters was observed. The direct-VPAP method was more rapid and precise while the BAM-MPN was more sensitive and may better recover stressed cells. The utilization of the VPAP probe for identification of V. parahaemolyticus sharply reduced the labor for either method compared to biochemical identification techniques used in earlier V. parahaemolyticus surveys.     

Production and characterization of monoclonal antibodies specific to chicken muscle soluble proteins

Three stable hybridoma cell lines (AH4, BC9 and CF2) have been produced which secrete monoclonal antibodies specific for chicken and turkey muscle proteins. Partial characterization by ELISA and SDS-PAGE immunoblotting indicated that the antibodies failed to cross-react with similar extracts of pork, beef, lamb, horse or rabbit. One of the cell lines (AH4) secreted a monoclonal antibody that was also capable of distinguishing between chicken and turkey by indirect ELISA.