Rennet-Induced Aggregation and Curd Formation from Skimmed Milk Powders Prepared under Different Sterilizing Conditions

Heat treatment during the production of skimmed milk powder causes denaturation of proteins, thereby affecting the physicochemical properties of the skimmed milk powder. To understand the effects of heat treatment on the sensitivity of the casein micelles in skimmed milk powders, low heating type (L), normal heating type (N), high heating type (H), and super-high heating type (SH), to reaction with rennet, rennet-induced curd formation was investigated. A well-developed network structure with wide spaces was observed only in the curd derived from the solution of type L skimmed milk powder. SDS–PAGE suggested that there was no difference in the amount of glycomacropeptide generated from κ-casein in the four types of skimmed milk powder, but casein micelles in the solution of type L skimmed milk powder formed aggregates most effectively. These results are discussed with respect to the thermal denaturation of proteins in skimmed milk powder.     

Immunodetection of added glycomacropeptide in milk formulas and milk powders

The present study aimed the detection of fraudulent manipulation of milk powder with a low cost component--whey powder, by applying the immunochromatographic assay to identify glycomacropeptide. Five commercial milk powder samples of various brands from the national market were analyzed: lactose enriched milk powder type 26, two whole milk powders, vitamin enriched milk powder and full cream milk powder. Our results showed additional whey (1-2%) in 60% of the selected samples after casein removal by precipitation with 20% trichloracetic acid. Another investigated sample--the enriched UHT milk for children aged 4-12 years--proved addition of whey. Other two commercial toddler formula milk powder samples of different brands were used for comparison for the presence of glycomacropeptide. The first sample which was regularly labeled as containing whey protein concentrate was found positive for glycomacropeptide in accordance with the label information, while the second one not containing whey proteins as specified by the product label, was found negative for glycomacropeptide, these two samples being in accordance with the actual legislation.     

阪崎肠杆菌能力验证样品均匀性和稳定性的研究

目的制备出以脱脂奶粉为基质的均匀性好、稳定性强的阪崎肠杆菌(Enterobacter sakazakii)能力验证样品。方法研究奶粉基质的粒度、奶粉和菌粉的混合比例,得到阪崎肠杆菌能力验证样品的最佳均匀性条件;研究包装形式及贮存温度对样品稳定性的影响,得到阪崎肠杆菌能力验证样品的最佳稳定性条件。结果要保证样品足够均匀,奶粉最佳粒径范围为120μmD180μm,1 g菌粉最多与300 g奶粉进行混合;贮存温度对样品稳定性有较大影响,高温明显降低样品稳定性;真空包装可以显著提高样品稳定性。结论以奶粉为基质的阪崎肠杆菌能力验证样品的制备能够更准确地考查乳品微生物检验人员的检测水平,为国内微生物能力验证水平的提高奠定了基础。     

Concentration of the proteins of skimmed milk by membraneless,isobaric osmosis

The concentration of skimmed milk proteins by polysaccharides such as gum arabic, arabinogalactan and apple pectin with a high content of methoxyl groups was studied. Investigation of the thermodynamic compatibility of skimmed milk proteins with these polysaccharides at different NaCl concentrations and pH has shown that above a certain polysaccharide concentration termed the ‘threshold of complete incompatibility’ the protein is almost completely excluded from the polysaccharide phase. Phase diagrams obtained for the systems: water-skimmed milk proteins-arabinogalactan, water-skimmed milk proteins-gum arabic and water-skimmed milk proteins-pectin, indicate that highly esterified apple pectin is superior to the other polysaccharides for concentrating skimmed milk proteins.The proposed method of concentration which may be called ‘membraneless isobaric osmosis' has a higher productivity and lower energy consumption than other methods of biopolymer concentration.     

A highly stable Yarrowia lipolytica lipase formulation for the treatment of pancreatic exocrine insufficiency

Yarrowia lipolytica lipase has been assumed to be a good candidate for the treatment of fat malabsorption in patients with pancreatic insufficiency. Nevertheless, no systematic studies on its stability under physiological conditions pertaining to the human GI (gastrointestinal) tract have been published. Stability of various Y. lipolytica lipase powder formulations at various physiological pH values as well as the effect of digestive proteases and bile salts on enzyme activity were investigated. Results were compared with those obtained from another competing fungal lipase sourced from Candida rugosa. Among the studied formulations, Y. lipolytica lipase stabilized with gum arabic and skimmed milk powder was the most promising powder formulation. Under acidic conditions (pH 3-5), this formulation showed higher stability than those observed with the other Y. lipolytica lipase formulations and C. rugosa lipase. In addition, in the presence of gum arabic and skimmed milk powder as additives, Y. lipolytica lipase exhibited markedly higher resistance to pepsin, trypsin and chymotrypsin actions. Resistance to proteolytic degradation by digestive proteases was also by far higher than that observed with C. rugosa lipase. Similar behaviour was, however, observed when these two fungal lipases were incubated with increased concentrations of bile salts. Residual lipase activity of both fungal lipases showed a slight decrease in NaTDC (sodium taurodeoxycholate) concentration above 4 mM. Consequently, Y. lipolytica lipase formulated with gum arabic and milk powder seemed to have great potential for use as a therapeutic tool for patients with pancreatic insufficiency.     

SENSORY PROFILING AND PRODUCT POSITIONING OF ROASTED AND GROUND (BREW) COFFEE AND SOLUBLE (INSTANT) COFFEE WITH AND WITHOUT ADDED FLAVOR

Coffee powders available commercially are of different qualities. The quality variations may be due to inherent quality of coffee beans, storage time and packaging materials used. Sensory profiles of brewed and soluble coffees were studied through profiling. Canonical discriminant analysis (CDA) used for positioning the different coffee samples showed that freshly made coffee from plantation arabica (PA), Pea berry (PB), PA with chicory (PAC), PB with chicory (PBC) and their blends viz. PA + PB and PAC + PBC occupied the quadrant where coffee aroma and overall quality rated higher. Other roasted & ground (R&G) coffee (market) samples were positioned where oily, fermented, musty, stale and caramelized notes dominated. In case of soluble coffee, the flavored coffee procured from the western market (S3, S6, S9 and S8) dominated the quadrant where other added flavor and oily notes dominated. The typical soluble (instant) coffee without any added flavor S10, S12 and S13 occupied another quadrant. The soluble coffee powder with spice incorporation took a separate quadrant where other added flavor and bitter taste dominated. The dominant quality attributes for the groups are different and are discussed in relation to the directional vectors.     

Genotyping of present-day and historical geobacillus species isolates from milk powders by high-resolution melt analysis of multiple variable-number tandem-repeat Loci

Spores of thermophilic Geobacillus species are a common contaminant of milk powder worldwide due to their ability to form biofilms within processing plants. Genotyping methods can provide information regarding the source and monitoring of contamination. A new genotyping method was developed based on multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) in conjunction with high-resolution melt analysis (MLV-HRMA) and compared to the currently used method, randomized amplified polymorphic DNA PCR (RAPD-PCR). Four VNTR loci were identified and used to genotype 46 Geobacillus isolates obtained from retailed powder and samples from 2 different milk powder processing plants. These 46 isolates were differentiated into 16 different groups using MLV-HRMA (D = 0.89). In contrast, only 13 RAPD-PCR genotypes were identified among the 46 isolates (D = 0.79). This new method was then used to analyze 35 isolates obtained from powders with high spore counts (>10(4) spores · g(-1)) from a single processing plant together with 27 historical isolates obtained from powder samples processed in the same region of Australia 17 years ago. Results showed that three genotypes can coexist in a single processing run, while the same genotypes observed 17 years ago are present today. While certain genotypes could be responsible for powders with high spore counts, there was no correlation to specific genotypes being present in powder plants and retailed samples. In conclusion, the MLV-HRMA method is useful for genotyping Geobacillus spp. to provide insight into the prevalence and persistence of certain genotypes within milk powder processing plants.     

A medium for the detection of Lancefield Group D cocci in skimmed milk powder by measurement of conductivity changes

A selective medium for the detection of Lancefield Group D cocci in skimmed milk powder by conductivity measurements was developed and evaluated using the Bactometer M123 and Malthus 128H systems. This medium promoted large changes in conductance and capacitance. The calibration curve of detection times vs concentration of Lancefield Group D cocci showed a linear correlation coefficient of 0.93 and the method gave comparable results in both conductivity instruments. Naturally contaminated samples containing c. 10(3) cfu/g of Lancefield Group D cocci gave detection times within 16-18 h which was sufficiently rapid for the medium to be used for the routine screening of skimmed milk powder.     

A New Criterion by Which to Distinguish Aspergillus sojae,a Koji-mold,from Related Taxa Producing Echinulate Conidia

Milk powders (commercial skim milk and modified milk powders) were stored at 30°C and 40°C for one month under various water activities (Aw), 0.23~0.82. After storage under Aw 0.57 and 0.80, they turned a dark brown color, and the contents of methionine and lysine had significantly decreased: methionine had been oxidized to methionine sulfoxide and lysine had changed to an unavailable form. The contents of arginine, tyrosine and tryptophan had also decreased, as had the contents of leucine and histidine in the skim milk powder. The tryptic digestibility of the milk powders had markedly decreased, and both the chymotryptic and peptic digestibilities of the skim milk powder had also decreased. The samples lost the property of being clotted by chymosin treatment.

No significant change was observed with casein under these conditions, nor with milk powders under dry conditions and Aw 0.23.     

A medium for the detection of Lancefield Group D cocci in skimmed milk powder by measurement of conductivity changes

A selective medium for the detection of Lancefield Group D cocci in skimmed milk powder by conductivity measurements was developed and evaluated using the Bactometer M123 and Malthus 128H systems. This medium promoted large changes in conductance and capacitance. The calibration curve of detection times vs concentration of Lancefield Group D cocci showed a linear correlation coefficient of 0.93 and the method gave comparable results in both conductivity instruments. Naturally contaminated samples containing c. 10³ cfu/g of Lancefield Group D cocci gave detection times within 16–18 h which was sufficiently rapid for the medium to be used for the routine screening of skimmed milk powder.     

Potato powders prepared by successive cooking-process depending on resistant starch content affect the intestinal fermentation in rats

The effects of resistant starch (RS) in dry potato powders prepared by various processes on intestinal fermentation in rats were assessed. Rats were fed raw potato powder (RP), blanched potato powder (BP), steamed potato powder (SP), or drum-dried potato powder (DP) for 4 weeks. The cecal RS content was significantly higher in the RP group than in the control diet (CN) group and other dry potato powder groups. Cecum pH was significantly lower in the RP group compared to the CN group, and was also significantly lower than that in the SP, BP, and DP groups. Lactic acid bacteria levels in the RP group were significantly higher than those in the CN group, and levels in the SP group also increased relative to the control group. Lactobacillus levels in the RP group were higher than in the CN and other dry potato powder groups. Cecal short-chain fatty acid (SCFA) concentrations in the RP group followed by the SP group exhibited significantly higher levels relative to the control levels. Dry potato powders containing RS produced during the cooking process may represent a useful food material that increases intestinal concentrations of SCFA and enhances the growth of certain lactic acid bacteria.     

嗜卷书虱的实验生态研究

在8种温度(17.5～35℃)及5种相对湿度(50%、60%、70%、80%和90%)条件下,以全麦粉、酵母粉、脱脂奶粉(10∶1∶1)为食料,系统研究了嗜卷书虱Liposcelis bostrychophila Badonnel实验种群生态学特性。获得了该虫在不同温、湿度条件下生长发育、生存和繁殖的一系列特性和参数,包括各虫态发育历期、存活率、发育起点温度、有效积温和平均繁殖力等,并建立了发育速率、存活率及繁殖力的理论模型。     

不同食物对嗜卷书虱发育和繁殖的影响

通过单头饲养方法综合比较了嗜卷书虱取食９种基本食物或食物组合的发育和繁殖情况,结果表明全麦粉最有利于该虫的发育和繁殖;在全麦粉中加入少量酵母粉和脱脂奶粉后,该虫发育明显加快、存活率及繁殖力均显著提高。此外还就该虫嗜食不同食物的原因进行了探讨。     

FUZZY MULTIATTRIBUTE DECISION MAKING APPROACH FOR DEVELOPMENT AND COMPARISON OF SOY FORTIFIED PANEER

Soyfortified paneer (SFP) samples prepared from blends containing different proportions of buffalo milk of varying fat content and soy milk (7.5 °B) were evaluated organoleptically for assessing the quality attributes like body and texture, flavor and taste, color and appearance and the overall acceptability. Sensory data were analyzed using fuzzy logic approach, which addresses the problem of data classification in a unified qualitative and quantitative manner. Results of the study indicated that the fuzzy multiattribute decision making approach provide an adequate and reliable system for product formulation and comparison, based on sensory data. The developed fuzzy mathematical model performed remarkably well in the evaluation and ranking of various SFP samples. The SFP sample made from blend of buffalo milk (4.5% fat) and soy milk (7.5 °B) in the proportion of 90:10 was found to be the most acceptable one for different classes of consumers irrespective of their preferences for a particular sensory quality attribute.     

Influence of bulk and tapped density on the determination of the thermal conductivity of powders and blends

The aim of this study was to evaluate a non-steady-state needle sensor to determine the thermal conductivity (lambda) of powders and their blends. It was investigated how lambda of different powders was influenced by (1) bulk vs tapped density, (2) moisture content of the powders, and (3) blending time of the powders. Different powders were evaluated: 2 lactose powders with different properties, a microcrystalline cellulose powder, a cornstarch powder, and 3 herbal extracts. The results show that the values of lambda are highly dependent on the bulk and tapped density of the powders. Bulk density measurements were generally not sensitive enough to detect the moisture content within a powder. The tapped density measurements were reliable and highly reproducible and could differentiate between the nature of a powder and the powder moisture content. Measurements of lambda were able to be used to monitor the powder blending process. To be able to use thermal conductivity measurements to characterize powder properties in quality control, the powder density must be defined because changes in density affect lambda. Using thermal conductivity as a measure for process analytical technology seems to be feasible and can add valuable information to the process under investigation.     

Silkworm pupae (Bombyx mori) and locusts as alternative protein sources for high-energy biscuits

This study explored the possibility of replacing skimmed milk – a core ingredient of High-energy biscuit (HEB), with edible-insects as inexpensive and sustainable alternative sources. HEB was formulated to meet the USAID 2016 (STD) nutritional standards and powdered locust and mulberry silkworm pupae (LP and SWP) at 15% inclusion, were used as alternative protein sources. Preliminary nutrients composition of the insect powders were examined. Physicochemical, sensory and microbial qualities of insect-enriched biscuits (LPB and SWPB) were evaluated and compared with that of skimmed milk (SMB) and STD. Spread ratios of the biscuits were between 7.8 and 11.6 – a technically acceptable range for biscuits. SWP possessed impressive amounts of protein (60.7 g/100 g), fat (23.5 g/100 g) and energy contents (498.93 kcal/100 g), while LP had slightly more fibre (1.4 g/100 g), ash (2.1 g/100 g) and carbohydrate (31.5 g/100 g). LPB and SWPB had relatively similar proximate compositions as SMB with slight variations, and all the HEBs were above USAID minimum standard. SWPB was marginally below requirements for Ca and Mg minerals, but both (SWPB and LPB) had more than twice the recommended pro-vitamin A (918.44 and 957.65 µg/100 g) and vitamin C contents (102.17 and 98.51 mg/100 g). All the samples received reasonably good sensorial rankings; but SMB’s aroma was preferred. Similarly, microbial quality assessment of the products reflected remarkable hygienic sample preparation. These results demonstrated that HEB of significant nutritional, sensorial and microbial qualities could be developed using edible-insects as alternative protein sources.     

Marine Fat Digestibility of its Fatty Acids in Young Calves

This paper describes the results from an experiment with four Jersey calves. The calves were bucket fed with a milk substitute consisting of skimmed milk powder and marine fat, supplemented with soyalecithin, vitamins and minerals. They were slaughtered after 30–32 days of such feeding. During the last two weeks a balance study was performed with a collection period of two days. Hay was given ad lib., and during the balance period the calves took between 125–150 g per day. The lipid content of the hay was considered negligible. Total content and distribution of fatty acids in the milk substitute are shown in Table 1. Table 2 shows the age of the calves, the total intake of lipid and fatty acids, and the total amount of fatty acids excreted with feces. The apparent digestibility coefficients of the individual fatty acids in each trial are shown in Table 3.     

冻干高活力纳豆芽胞杆菌菌粉保护剂的筛选和优化

【目的】对冻干高活力纳豆芽胞杆菌菌粉保护剂进行筛选和优化研究,提高菌粉活菌存活率。【方法】采用单因素实验和正交实验设计,通过测定活菌存活率,筛选出最佳保护剂的配方;并研究采用优化后冻干保护剂制备的菌粉在20°C、4°C、25°C下的保存稳定性。【结果】纳豆芽胞杆菌的有效保护剂是:脱脂乳粉、甘露醇、L-抗坏血酸钠。最佳冷冻干燥保护剂配方是:脱脂乳粉10%+甘露醇4%+L-抗坏血酸钠1%,存活率达到91.63%。菌粉在20°C、4°C、25°C下保存12个月后,存活率分别为:88.79%、70.16%和10.52%,说明菌粉在20°C和4°C下保存稳定性较好,25°C下稳定性比较差。【结论】对纳豆芽胞杆菌冻干菌粉保护剂的优化,对纳豆芽胞杆菌的应用、活菌产品的质量稳定及新产品的研发均有一定的指导意义。     

Comparison of different blocking agents and nitrocelluloses in the solid phase detection of proteins by labelled antisera and protein A

Five different brands of nitrocellulose (NC), each of pore size 0.45 micron and without adsorbed antigen, bound different amounts of two labelled antisera and labelled protein A. Experiments with some non-ionic surface active agents and proteins showed that milk powder and bovine serum albumin were the most effective agents for blocking non-specific binding of labelled protein to NC. With some of the NCs, Nonidet P-40 (NP-40) and Tween 20 were almost as effective as milk powder. The protein-binding capacity of unblocked NC and the level of protein binding after blocking were found to be inversely proportional to the pore size of the NC. A comparison of blocking agents in an immunoassay with pollen proteins adsorbed to NC discs revealed that the highest specific uptakes of antiserum occurred with NP-40 and Tween and not with any of the protein blocking agents such as milk powder. Hence, for the detection of proteins using NC-based assays (but not necessarily following electroblotting), the best choices would appear to be: NC of pore size 0.45 micron; a brand of NC that provides a suitable balance between protein binding capacity and non-specific uptake of protein after blocking; a non-ionic detergent such as NP-40 or Tween 20.