Effect of irradiation and other processing methods on in-vitro digestibility of rapeseed protein

Abstract. Effect of irradiation (1 kGy), autoclaving (121°C at 103.5 kPa for 5, 10, 15, 20, 25 and 30 min), dry heating (121°C for 5, 10, 15, 20, 25, 30 and 60 min), sprouting (36 h) and their combination on in-vitro digestibility of rapeseed protein was studied. Digestibility was significantly affected by processing methods (P < 0.05). Digestibility of untreated rapeseed protein was 85.7%. Irradiation alone and irradiation plus dry heating showed no effect on the digestibility, while irradiation plus autoclaving markedly improved (88.9%) the digestibility. The digestibility was influenced by the time of autoclaving and dry heating. Maximum value for in-vitro digestibility was recorded for 60 min of dry heating (91.8%). Sprouting of rapeseed exhibited a significant decrease (82.8%) in the digestibility.     

Active packaging of ground beef patties by edible zein films incorporated with partially purified lysozyme and Na2EDTA

In this study, antimicrobial activity of zein films incorporated with partially purified lysozyme and disodium ethylenediaminetetraacetic acid (Na₂EDTA) has been tested on selected pathogenic bacteria and refrigerated ground beef patties. The developed films containing 700 μg cm^?2 lysozyme and 300 μg cm^?2 Na₂EDTA showed antimicrobial activity on Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella typhimurium. The application of lysozyme and Na₂EDTA incorporated zein films on beef patties significantly decreased total viable counts (TVC) and total coliform counts after 5 days of storage compared to those of control patties (P < 0.05). Zein films incorporated with lysozyme and Na₂EDTA or Na₂EDTA alone significantly slowed down the oxidative changes in patties during storage (P < 0.05). Redness indices of patties coated with zein films were significantly lower than those of uncoated control patties during storage (P < 0.05). This study demonstrated the potential usage of zein films containing lysozyme and Na₂EDTA for active packaging of refrigerated meat products.     

Proteolysis in goat cheese made from raw,pasteurized or pressure-treated milk

Primary and secondary proteolysis of goat cheese made from raw (RA), pasteurized (PA; 72 °C, 15 s) and pressure-treated milk (PR; 500 MPa, 15 min, 20 °C) were examined by capillary electrophoresis, nitrogen fractionation and HPLC peptide profiles. PA milk cheese showed a more important hydrolysis (P<0.05) of α_s1-casein than RA milk cheese at the first stages of ripening (15 days), while PR milk cheese had a level between those seen in PA and RA milk cheeses. Degradation of β-casein was more important (P<0.05) in PA and PR than in RA milk cheeses at 15 days of ripening. However, from thereon β-casein in PR and RA milk cheeses was hydrolyzed at essentially similar rates, but at lower rates (P<0.05) than in PA milk cheeses. Pressure treatment could induce proteolysis of β-casein in a way, which is different from that produced by heat treatment. There was an increase in 4.6-soluble nitrogen (WSN) and in trichloroacetic acid (TCASN) throughout ripening in cheeses, but higher contents (P<0.05) in PA and PR milk cheeses at the end of ripening were observed. PR milk cheeses contained considerably higher content (P<0.05) of free amino acids than RA or PA milk cheeses. In general, heat and pressure treatments had no significant effect on the levels of hydrophobic and hydrophilic peptides.     

Effect of flaxseed processing on its true metabolizable energy values for adult chicken

The objective of the present experiment was to study the effect of flaxseed processing on nitrogen corrected true metabolizable energy (TME_n) values for adult roosters. Flaxseed was processed as pelleted, autoclaved or microwave roasted. Leghorn roosters were used for the TME determination procedure. The TME_n value of flaxseed batch A, 14.48 MJ kg^?1 DM, was significantly (P < 0.05) increased to 17.89 MJ kg^?1 DM by three‐time repeat‐pelleting, or to 18.07 MJ kg^?1 dry matter (DM) by autoclaving, respectively. Microwave roasting also significantly (P < 0.05) increased the TME_n value of flaxseed batch B by 22%. The TME_n improvement observed due to processing was accompanied by increased ether extract utilization. The apparent ether extract digestibility of flaxseed batch A, 61.2%, was very significantly (P < 0.01) increased to 81.5 and 83.2% by processing as repeat‐pelleting and autoclaving, respectively. Microwave roasting also significantly (P < 0.05) increased the apparent digestibility of ether extract for flaxseed batch B from 49.1 to 64.4%. Proper flaxseed processing as pelleting, autoclaving and microwave roasting led to higher TME_n values for Leghorn roosters, mainly as the result of increased ether extract utilization. Copyright © 2004 Society of Chemical Industry     

Physical properties and hypoglycaemic activity of biscuits as affected by the addition of stigma maydis extract

The study aimed to evaluate the potential ingredient of stigma maydis (S.M.) as a hypoglycaemic functional food. In the present study, waxy corn flour and corn-resistant starch were used to make biscuits; the influence of S.M. extracts (aqueous extract, SMA; ethanol extract, SME; mixed solvent extract, SMM) on the physical features and in vitro digestibility of biscuit were surveyed. In the meantime, the α-amylase and α-glucosidase inhibition of different S.M. extracts were analysed. Compared with the control dough, 5% ethanol S.M. extract (SME2) dough was observed to have the lowest storage modulus (G'), loss modulus (G"), hardness, water absorption capacity (P < 0.05), while creep strain was the highest (P < 0.05). Adding S.M. extracts could significantly reduce the L*, b* value and increase the a* value of biscuits. Besides, the S.M. extracts could decrease the glycaemic index (G.I.) of biscuits and reduce postprandial blood glucose levels. The GI of SMA1, SMA2, SME1, SME2, SMM1 and SMM2 was decreased to 62.47, 55.17, 51.46, 44.89, 53.05 and 50.11 respectively. Further, the addition of S.M. extract could show a certain inhibitory rate of α-amylase and α-glucosidase when added to biscuits. The inhibition ratio of 5% extract (SMA2, SME2 and SMM2) biscuit was higher than that of 1% extract (SMA1, SME1 and SMM1) biscuit (P < 0.05). As a natural functional component, S.M. extract could be a potential food supplement for type II diabetic mellitus.     

Short communication: Genetic parameters for milk protein composition predicted using mid-infrared spectroscopy in the French Montbéliarde,Normande, and Holstein dairy cattle breeds

Genetic parameters for the major milk proteins were estimated in the 3 main French dairy cattle breeds (i.e. Montbéliarde, Normande, and Holstein) as part of the PhénoFinlait program. The 6 major milk protein contents as well as the total protein content (PC) were estimated from mid-infrared spectrometry on 133,592 test-day milk samples from 20,434 cows in first lactation. Lactation means, expressed as a percentage of milk (protein contents) or of protein (protein fractions), were analyzed with an animal mixed model including fixed environmental effects (herd, year × month of calving, and spectrometer) and a random genetic effect. Genetic parameter estimates were very consistent across breeds. Heritability estimates (h²) were generally higher for protein fractions than for protein contents. They were moderate to high for α_S1-casein, α_S2-casein, β-casein, κ-casein, and α-lactalbumin (0.25 < h² < 0.72). In each breed, β-lactoglobulin was the most heritable trait (0.61 < h² < 0.86). Genetic correlations (r_g) varied depending on how the percentage was expressed. The PC was strongly positively correlated with protein contents but almost genetically independent from protein fractions. Protein fractions were generally in opposition, except between κ-casein and α-lactalbumin (0.39 < r_g < 0.46) and κ-casein and α_S2-casein (0.36 < r_g < 0.49). Between protein contents, r_g estimates were positive, with highest values found between caseins (0.83 < r_g < 0.98). In the 3 breeds, β-lactoglobulin was negatively correlated with caseins (?0.75 < r_g < ?0.08), in particular with κ-casein (?0.75 < r_g < ?0.55). These results, obtained from a large panel of cows of the 3 main French dairy cattle breeds, show that routinely collected mid-infrared spectra could be used to modify milk protein composition by selection.     

Effects of moist heat treatment on ruminal nutrient degradability of sunflower seed

A study was conducted to determine the effects of moist heat treatment (autoclaving at 127 °C with a steam pressure of 117 kPa for 10, 20 and 30 min) of sunflower seed on crude protein (CP) fractions, ruminal dry matter (DM) and CP degradabilities, and ruminal disappearance of amino and fatty acids. Two ruminally fistulated cows were used in a randomised complete block design. Heating of sunflower seed decreased soluble protein and increased neutral detergent‐insoluble protein, with little effect on acid detergent‐insoluble protein. Results of the in sacco study showed that moist heat treatment decreased (cubic effect, P < 0.05) ruminal degradability of DM and CP of sunflower seed. Ruminal undegraded CP of raw sunflower seed was low (84 g kg^?1 of CP) and increased (cubic effect, P < 0.05) by 139, 143 and 164% as the heating time increased from 0 to 10, 20 and 30 min respectively. Ruminal disappearance of all amino acids (following 12 h of incubation) was greater (P < 0.05) for raw than for heated sunflower seed. Similar results were also observed for ruminal disappearance of fatty acids. It was concluded that moist heat treatment decreased ruminal DM and CP degradability of sunflower seed (by 17 and 19% respectively) and thus increased the concentrations of amino acids and polyunsaturated fatty acids available for digestion in the small intestine. Copyright © 2003 Society of Chemical Industry     

Characteristics of edible films made from dairy proteins and zein hydrolysate cross-linked with transglutaminase

The main objectives of this research were to develop whey protein or casein films incorporating zein hydrolysate and also cross‐linked by transglutaminase as to well as characterize the physical and mechanical properties of the film. Zein hydrolysate decreased the solubility of the whey protein film (P < 0.05), while treatment with transglutaminase did not change the solubility of the film significantly. Electrophoresis patterns demonstrated that casein molecules were cross‐linked by transglutaminase and the extent of this cross‐linkage was further increased when zein hydrolysate was added. In addition, the use of zein hydrolysate decreased the tensile strength of the whey protein film by 35–45%. The elongation of the casein film was increased by 41% because of the action of transglutaminase and zein hydrolysate (P < 0.05). The water vapour permeability of the films was not significantly different. As the addition of zein hydrolysate and treatment with transglutaminase improved the flexibility of the films, the level of plasticizer required to maintain film flexibility could be reduced without sacrificing their water vapour permeability.     

Different oilseed supplements alter fatty acid composition of different adipose tissues of adult ewes

Twenty-five mature Small Tail Han ewes were used to investigate the effects of supplemental oilseeds in the diet (sunflower seed, safflower seed, rapeseed, and linseed) on fatty acid composition in different tissues (longissimus lumborum muscle, tail fat, subcutaneous back fat and kidney fat). Averaged over tissue, safflower and sunflower seed was most effective (P < 0.05) in enhancing the concentration of conjugated linoleic acid compared to rapeseed, linseed, and control (1.35% and 1.15% vs. 0.80%, 0.80%, and 0.75%, respectively). Linseed supplemented ewes had lesser n−6/n−3 value (2.48, P < 0.05) compared to sunflower and safflower supplemented ewes (6.12 and 3.90, respectively). Fatty acid composition for most major fatty acids differed among tissues (P < 0.05) but tissue differences varied depending on oilseed supplement (P < 0.05). Proportions of conjugated linoleic acid were greatest in tail fat (1.54% vs. 0.82%, 0.79% and 0.70% for kidney, back, and muscle fat, P < 0.05) as were total unsaturated fatty acids (49.1% vs. 42.4%, 36.7% and 33.4% for muscle, back, and kidney fat, P < 0.05) and tail fat was the most responsive tissue to improvement in fatty acid profile through supplementation. Beneficial fatty acid content of tissues can be increased by oilseed supplementation, but the magnitude of increase varies according to tissue.     

Effects of exogenous fibrolytic enzymes on epiphytic microbial populations and in vitro digestion of silage

Epiphytic microbial populations, reducing sugar (RS) concentrations and in vitro fermentation were measured in unsterilised and sterilised barley silage and corn silage treated with an exogenous enzyme preparation. Enzyme treatments comprised spraying silages (10 ml kg^?1 DM) with a xylanase/β‐glucanase enzyme preparation or with water or autoclaved enzyme (controls). In Experiment 1, autoclaving the silages increased (P < 0.05) concentrations of RS present 24 h after treatment. Enzymes increased (P < 0.05) RS in both fresh and autoclaved silages, more so (P < 0.05) with autoclaving than without. Autoclaved enzymes did not affect RS concentrations relative to the (water) controls. Aerobic exposure of corn silage numerically increased microbial numbers; no microbial viability was detected in autoclaved silages. Enzymes increased (P < 0.05) total bacterial counts in all silage types, and this effect was more pronounced on aerobically exposed silage. In Experiment 2, RS concentrations were determined 0 and 24 h after enzyme treatment of silages unsterilised or sterilised with ethylene oxide (EO). Irrespective of EO or silage type, RS concentrations were higher (P < 0.05) 24 h after enzyme treatment than immediately after (0 h). In enzyme‐treated silages, 24 h RS concentrations were higher (P < 0.05) with EO than without. Reducing epiphytic microbiota by sterilisation conserved enzyme‐liberated RS in the silages. Aerobic exposure before applying enzymes enhanced RS‐associated increases in microbial numbers. Enzymes effectively released RS from silages, but utilisation of the RS by inherent epiphytic micro‐organisms may limit their availability to the ruminant. By releasing RS, exogenous enzymes may encourage silage deterioration if the interval between treatment and feeding is excessive. During in vitro incubation of freeze‐dried silages (Experiment 3), incorporation of ¹⁵N into microbial N was decreased by enzyme applied to fresh silage (before drying), but increased by enzyme applied after the silage had been dried. Moisture level of feeds and epiphytic microbial populations may influence the effectiveness of enzyme treatment for enhancing utilisation of feeds by ruminants. For the Department of Agriculture and Agri‐Food, Government of Canada. © Minister of Public Works and Government Services Canada 2002. Published for SCI by John Wiley & Sons, Ltd     

Proteomic and peptidomic study of proteolysis in quarter milk after infusion with lipoteichoic acid from Staphylococcus aureus

Mastitic milk is associated with increased bovine protease activity, such as that from plasmin and somatic cell enzymes, which cause proteolysis of the caseins and may reduce cheese yield and quality. The aim of this work was to characterize the peptide profile resulting from proteolysis in a model mastitis system and to identify the proteases responsible. One quarter of each of 2 cows (A and B) was infused with lipoteichoic acid from Staphylococcus aureus. The somatic cell counts of the infused quarters reached a peak 6 h after infusion, whereas plasmin activity of those quarters also increased, reaching a peak after 48 and 12 h for cow A and B, respectively. Urea-polyacrylamide gel electrophoretograms of milk samples of cow A and B obtained at different time points after infusion and incubated for up to 7 d showed almost full hydrolysis of β- and α_S1-casein during incubation of milk samples at peak somatic cell counts, with that of β-casein being faster than that of α_S1-casein. Two-dimensional gel electrophoretograms of milk 6 h after infusion with the toxin confirmed hydrolysis of β- and α_S1-casein and the appearance of lower-molecular-weight products. Peptides were subsequently separated by reversed-phase HPLC and handmade nanoscale C₁₈ columns, and identified by matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry. Twenty different peptides were identified and shown to originate from α_s1- and β-casein. Plasmin, cathepsin B and D, elastase, and amino- and carboxypeptidases were suggested as possible responsible proteases based on the peptide cleavage sites. The presumptive activity of amino- and carboxypeptidases is surprising and may indicate the activity of cathepsin H, which has not been reported in milk previously.     

Effects of variousMicrococcus strains on the ripening and organoleptic characteristics of Arzúa cow's-milk cheese

Ten batches of Arzúa, a soft cow's-milk cheese produced in northwest Spain, were prepared from pasteurized milk. Two (control) batches (CB) were made with a commercial starter containingLactococcus lactis subspecieslactis andcremoris. Another eight batches (MB) were made with the commercial starter plus one of eightMicrococcus spp. strains previously isolated from raw-milk Arzúa cheeses. In all MB, β-casein degradation over the 30-day ripening period was more pronounced (mean 31%) than in the CB (mean 12%). α_S1-Casein degradation was highly variable in the MB, though mean degradation over the ripening period (75%) was similar to that observed in the CB (73%). Similarly, volatile fatty acid (VFA) content was highly variable in the MB, with the mean content at 30 days (3.8 mEq per 100 g) being higher than in the CB (1.6 mEq per 100 g). Rheological characterization of the cheeses (by uniaxial compression) revealed significant differences between batches, with some samples fracturing under the compression pressure applied and others not. Sensory evaluation also revealed significant differences. “Non-milk” aromas were more frequently detected in batches made with lipolytic micrococcal strains. Betweenbatch differences in tastes and texture were also detected. Multiple correlation analysis of the data obtained at day 15 of ripening revealed statistically significant positive correlations (r>0.70) between α_S1-casein content and dry matter content, between α_S1-casein content and sensorially evaluated firmness, and between VFA content and sensorially evaluated rancidity. Statistically significant negative correlations between sensorially evaluated firmness and the ratio of α_S1-I content to α_S1-casein content were detected. The results of this study suggest a need for further studies aimed at selecting those strains which could be most suitable for the production of Arzüa cheeses; due to their effects on texture, α_S1-caseinolytic strains seem to be more appropriate than β-caseinolytic ones.     

水解反应对菜籽蛋白生物利用度的影响研究

研究了菜籽蛋白经酶解后在生物体内的生物利用,考察了水解度对菜籽蛋白生物利用度的影响。将雄性SD大鼠64只,随机分成8组,即无氮组、酪蛋白组、菜籽蛋白组、水解度(DH)为4%、8%、12%、16%、20%的水解组,每组8只。大鼠在膳食平衡3 d之后,开始进行代谢试验,测其真消化率、表观消化率、净蛋白利用率、生物价指标。连续饲喂21 d之后,记录SD大鼠的体重变化和日粮消耗量,计算蛋白功效比值和净蛋白比。结果表明,真消化率、表观消化率、蛋白功效比值、净蛋白比和SD大鼠体重随水解度的增大有降低的趋势,DH 4%组与菜籽蛋白组相比无显著差异(P0.05)。菜籽蛋白水解之后的净利用率要高于未水解的蛋白,但差异不显著(P0.05)。与菜籽蛋白组相比,DH 4%组的生物价就已经有了显著的提高(P0.05);而与水解度更高的组相比,DH 4%组生物价无显著变化(P0.05)。综合考虑,说明DH 4%组具有较高的生物利用度,是适合人类食用的优质蛋白。     

Whole-genome association study for milk protein composition in dairy cattle

Our objective was to perform a genome-wide association study for content in bovine milk of α_S1-casein (α_S1-CN), α_S2-casein (α_S2-CN), β-casein (β-CN), κ-casein (κ-CN), α-lactalbumin (α-LA), β-lactoglobulin (β-LG), casein index, protein percentage, and protein yield using a 50K single nucleotide polymorphism (SNP) chip. In total, 1,713 Dutch Holstein-Friesian cows were genotyped for 50,228 SNP and a 2-step association study was performed. The first step involved a general linear model and the second step used a mixed model accounting for all family relationships. Associations with milk protein content and composition were detected on 20 bovine autosomes. The main genomic regions associated with milk protein composition or protein percentage were found on chromosomes 5, 6, 11, and 14. The number of chromosomal regions showing significant (false discovery rate <0.01) effects ranged from 3 for β-CN and 3 for β-LG to 12 for α_S2-CN. A genomic region on Bos taurus autosome (BTA) 6 was significantly associated with all 6 major milk proteins, and a genomic region on BTA 11 was significantly associated with the 4 caseins and β-LG. In addition, regions were detected that only showed a significant effect on one of the milk protein fractions: regions on BTA 13 and 22 with effects on α_S1-CN; regions on BTA 1, 9, 10, 17, 19, and 28 with effects on α_S2-CN; a region on BTA 6 with an effect on β-CN; regions on BTA 13 and 21 with effects on κ-CN; regions on BTA 1, 5, 9, 16, 17, and 26 with effects on α-LA; and a region on BTA 24 with an effect on β-LG. The proportion of genetic variance explained by the SNP showing the strongest association in each of these genomic regions ranged from <1% for α_S1-CN on BTA 22 to almost 100% for casein index on BTA 11. Variation associated with regions on BTA 6, 11, and 14 could in large part but not completely be explained by known protein variants of β-CN (BTA 6), κ-CN (BTA 6), and β-LG (BTA 11) or DGAT1 variants (BTA 14). Our results indicate 3 regions with major effects on milk protein composition, in addition to several regions with smaller effects involved in the regulation of milk protein composition.     

Effect of radiation and other processing methods on protein quality of sunflower meal

The effects of gamma irradiation from a ⁶⁰Co source (10 and 20 kGy), dry heating (121 °C for 10, 20 and 30 min), autoclaving (121 °C at 103.5 kPa for 10, 20 and 30 min) and their combination on chlorogenic acid, soluble protein, available lysine and in-vitro protein digestibility of sunflower meal were studied. The moisture content of the raw sample was 78 g kg⁻¹ as is and on a dry matter basis. The meal contained 26.7 g kg⁻¹ chlorogenic acid, 330 g kg⁻¹ crude protein, 78.5% soluble protein and 2.63 g 16 g N⁻¹ available lysine. Digestibility of raw meal was 81.5%. Chlorogenic acid, soluble protein and available lysine of raw meal decreased during dry heating, autoclaving and radiation processing. The digestibility was significantly affected by processing method (P < 0.05), as well as by the time of dry heating and autoclaving. The influence of combination methods revealed that irradiation alone had a little effect on chlorogenic acid and in-vitro protein digestibility. Autoclaving plus irradiation up to 20 kGy markedly improved the digestibility (90%). Therefore, the results suggested that the combination of autoclaving for 10 min plus irradiation up to 20 kGy has a beneficial effect on the protein quality of sunflower meal with little effect on its content of soluble protein, available lysine and markedly reduced chlorogenic acid by 87%, more than other processing methods. © 1999 Society of Chemical Industry     

Lipolysis and proteolysis profiles of fresh artisanal goat cheese made with raw milk with 3 different fat contents

The objective of this study was to describe the proteolysis and lipolysis profiles in goat cheese made in the Canary Islands (Spain) using raw milk with 3 different fat contents (0.5, 1.5, and 5%) and ripened for 1, 7, 14, and 28 d. β-Casein was the most abundant protein in all cheeses and at all ripening times. Quantitative analysis showed a general decrease in caseins as ripening progressed, and degradation rates were higher for α_S1-casein than for β-casein and α_S2-casein. Furthermore, the degradation rate during the experimental time decreased with lower fat contents. The α_S2-casein and α_S1-casein levels that remained in full-fat and reduced-fat cheeses were less than those in low-fat cheese. In contrast, β-casein also showed degradation along with ripening, but differences in degradation among the 3 cheese types were not significant at 28 d. The degradation products increased with the ripening time in all cheeses, but they were higher in full-fat cheese than in reduced-fat and low-fat cheeses. The free fatty acid concentration per 100 g of cheese was higher in full-fat cheese than in reduced- and low-fat cheese; however, when the results were expressed as milligrams of free fatty acids per gram of fat in cheese, then lipolysis occurred more rapidly in low-fat cheese than in reduced- and full-fat cheeses. These results may explain the atypical texture and off-flavors found in low-fat goat cheeses, likely the main causes of non-acceptance.     

Compositional and nutritional studies on edible wild mushroom from northeast India

Two species of mushrooms Schizophyllum commune and Lentinus edodes from Northeast India were assessed for their nutritive value. Protein contents of S. commune (16%) and L. edodes (23%) were high, but fat content was low (2%) in both the mushrooms. Oleic and linoleic acids accounted for 72–77% of the total fat in both the mushrooms. Essential amino acid contents of S. commune and L. edodes were 34% and 39%, respectively. The chemical scores of S. commune (28) and L. edodes (29) were low compared to whole egg protein. Methionine was the limiting amino acid in both the mushrooms. Protein quality evaluation by NPR (net protein ratio), NPU (net protein utilization) and TDP (true digestibility of protein), showed that the mushrooms were comparatively much lower then casein in all the parameters examined. Animals on L. edodes showed significantly (p < 0.05) higher NPR, RNPR, and NPU than animals on the S. commune diet. True protein digestibility of the L. edodes diet was also significantly (p < 0.05) higher than the S. commune diet.     

QUALITY PRESERVATION OF COMMERCIAL FISH BALLS WITH ANTIMICROBIAL ZEIN COATINGS

ABSTRACT

To enhance the practical application of active edible coatings in the food industry, edible zein coatings incorporated with nisin (54.4 AU/cm²) or nisin/ethylenediaminetetraacetic acid (EDTA; 568 µg/cm²) were used to preserve the quality of commercially manufactured fish balls. The microbial load, total basic volatile nitrogen (TVB‐N) content and weight loss were served as quality indicators. The increase of microbial load of fish balls coated with antimicrobial zein during a 15‐day refrigeration storage period was less than 1 log cfu/g, while the microbial load increased about 3 log cfu/g for the control group without the coating treatment. The formation of TVB‐N was significantly (P < 0.05) reduced when fish balls were coated with antimicrobial zein. With or without antimicrobial agent, coated fish balls exerted significantly (P < 0.05) less weight loss than uncoated fish balls.

PRACTICAL APPLICATIONS

Although edible coatings or films containing bioactive substance have been intensively studied over the last few decades, most of these, still, have not had widespread commercial applications because the majority of studies were conducted with food‐simulated systems or food samples produced in laboratory. The fish balls commercially manufactured in a fishery product factory was used to demonstrate the efficacy of antimicrobial edible coating will enhance the confidence of food manufactures to apply the technology in their products.     

Short communication: Milk protein genetic variation and casein haplotype structure in the Original Pinzgauer cattle

Milk protein genetic polymorphisms are often used for characterizing domesticated mammalian species and breeds, and for studying associations with economic traits. The aim of this work was to analyze milk protein genetic variation in the Original Pinzgauer, a dual-purpose (dairy and beef) cattle breed of European origin that was influenced in the past by human movements from different regions as well as by crossbreeding with Red Holstein. A total of 485 milk samples from Original Pinzgauer from Austria (n = 275) and Germany (n = 210) were typed at milk proteins α_S1-casein, β-casein, κ-casein, α-lactalbumin, and β-lactoglobulin by isoelectrofocusing to analyze the genetic variation affecting the protein amino acid charge. The Original Pinzgauer breed is characterized by a rather high genetic variation affecting the amino acid charge of milk proteins, with a total of 15 alleles, 12 of which were found at a frequency >0.05. The most polymorphic protein was β-casein with 4 alleles detected. The prevalent alleles were CSN1S1*B, CSN2*A², CSN1S2*A, CSN3*A, LGB*A, and LAA*B. A relatively high frequency of CSN1S2*B (0.202 in the whole data set) was found, mainly occurring within the C-A²-B-A haplotype (in the order CSN1S1-CSN2-CSN1S2-CSN3), which seems to be peculiar to the Original Pinzgauer, possibly because the survival of an ancestral haplotype or the introgression of Bos indicus.     

The effect of dephosphorylation and succinylation on the properties of casein proteins adsorbed to the surface of latex particles

Dephosphorylation decreased the absolute zeta potential and diameters of α_S1-casein-coated latex particles. Similar effects were observed for α_S1-casein dephosphorylated prior to or after adsorption. If α_S1-casein adopts a loop arrangement at hydrophobic surfaces, then it appears that dephosphorylation causes the loop to move closer to the surface. Dephosphorylation caused a larger change for particles coated with α_S1-casein than β-casein, whereas small changes were observed for κ-casein, consistent with the phosphorylation levels of these caseins. Succinylation increased the absolute value of zeta potential and the diameters of α_S1-casein-coated latex particles. A higher level of succinylated α_S1-casein was required to saturate the particle surface. It is proposed that succinylated α_S1-casein has the C-terminal region adsorbed to the particle surface and N-terminal region extending from the surface as a hair. Results of this study help explain the effect of dephosphorylation and succinylation on the functional properties of the caseins, particularly in stabilising emulsions.