PROXIMATE AND LIPID COMPOSITION OF NONDAIRY IMITATION MILK IN COMPARISON WITH MILK

Comparative studies of milk and nondairy imitation milks showed that their proximate compositions were similar. Qualitative and quantitative studies revealed that saturated fatty acids were abundant in milk, while unsaturated fatty acids (C _18:1 and C _18:2 ) were predominant in nondairy imitation milks. This was confirmed by the higher melting points of the fat fractions of milk compared with those of nondairy imitation milks. Finally, lipid peroxidation level of samples were low as determined by the 2-thiobarbituric acid test.     

Removal of penicillin G from contaminated milk by ultrafiltration

Penicillin G purposedly added to whole raw milk at concentrations from .05 to .20 IU/ml was removed to undetectable levels by a combination of ultrafiltrations and permeate washes. After penicillin removal, whole milk 3:1 vol/vol concentrated retentates were reconstituted to milk with antibiotic-free permeate with little change in composition and with very good to excellent flavor. Washing 3:1 vol/vol concentrated retentates from penicillin-contaminated milks with water also removed penicillin to an undetectable level but changed the composition of product, which displayed a flat flavor.     

Millet Processing for Improved Stability and Nutritional Quality Without Functionality Changes

Whole millet adjusted to 15% moisture was gradually heated to 97°C over 12 min by passing through a steam-jacketed paddle conveyer to inactive lipid enzymes. Both processed and unprocessed millet were milled to 50% and 80% extraction flours. The 80% flour contained germ fractions, which resulted in much higher protein, lipid, thiamine, riboflavin, niacin, iron, zinc, available lysine, and protein efficiency ratios than the 50% flour. After 49°C storage, peroxide and fat acidity values were lower and flavor scores higher for processed than for unprocessed millet flours. No differences between processed and unprocessed flours were found in birefringence, water absorption and solubility, viscoamylograph values, or in their use in several traditional foods.     

The effect of starch based fat substitutes on the microstructure of set-style yogurt made from reconstituted skimmed milk powder

Seven different types of starch based fat substitutes were used for the production of set-style yogurt from reconstituted skimmed milk powder. The yogurt milks contained 14.0–15.8% total solids, 7.3–9.1% carbohydrates, 5.3–5.6% protein and 1.0–1.2% ash. The fat content of all the batches was 0.1% except the control (1.5%), which was made with anhydrous milk fat. Yogurts made with P-Fibre 150 C and 285 F contained 0.5 and 1.1% fibre respectively. Decrease in whey syneresis and increase in firmness in all the yogurts were observed during 20 days' storage at 5°C. Yogurt made with P-Fibre 150 C had the least amount of whey syneresis. Scanning electron microscopy and transmission electron microscopy revealed subtle differences in the microstructure of set-style yogurts due to the different starch based fat substitute used. 'Spikes' and 'hair' like structures were evident around the casein micelles in the milk base. They were lightly stained when compared with the caseins. Their detection in the yogurt was very difficult and only P-150 C and P-285 F substitutes were visualized whereas the others could not be detected even when their concentration was increased to 5%. Yogurt made with Lycadex® 100 was more porous and had slightly larger void spaces filled with milk serum. The use of a higher concentration (5%) of fat substitutes increased the firmness, but impaired the flavour and mouth feel of the yogurts.     

Concentrations of cadmium and lead in different types of milk

 Concentrations of Pb and Cd were determined in samples of human, raw and pasteurized cow's and goat's milk and powdered infant formula. The following mean Cd concentrations (and ranges) were recorded: in human milk, 2.70 μg/l (0.6–11.3, n=55); in raw cow's milk, 4.88 μg/l (0.7–23.1, n=47); in pasteurized cow's milk, 4.30 μg/l (3.4–5.9, n=6); in goat's milk, 7.81 μg/l (1.0–18.4, n=38); and in powdered, infant formula, 3.81 μg/l (3.4–4.1, n=5). The concentrations (and ranges) of Pb were: in human milk, 8.34 μg/l (0.1–32.3, n=55); in raw cow's milk, 14.82 μg/l (1.3–39.1, n=28); in pasteurized cow's milk, 10.25 μg/l (6.9–19.6, n=6); in goat's milk, 11.86 μg/l (0.4–38.5, n=36); and in powdered, infant formula, 8.30 μg/l (5.1–10.6, n=5). Our data were within the normal ranges for each kind of milk. The Cd and Pb concentrations in goat's milk were significantly higher than the concentrations observed in the other milks, whereas human milk and powdered infant formula presented the lowest Cd and Pb concentrations. A considerable decrease in the concentration of Cd with the stage of lactation was observed. The concentrations of Cd and Pb in human, cow's and goat's milk also varied according to the time of year. The concentrations of Pb and Cd in the different milks did not present any risk to human health (infants or adults). Received: 26 May 1998     

Milk composition and flavor under different feeding systems: A survey of dairy farms

Understanding the influence of regional dietary factors on the flavors of milk and dairy products will provide consumers with more options and promote the conservation of regional resources and the original terroir. The objective of this study was to evaluate the influence of regional differences in feeding systems on the composition, fatty acid content, and flavor of pasteurized milk at the farm level. Nine dairy farms using grass silage (GS), 6 farms using maize silage (MS), and 4 farms using by-products (BP) as the characteristic feed components were chosen for this survey. Fresh milk was sampled once per month from September 2008 to February 2009 at each dairy farm. The percentages of GS, MS, and BP (soybean curd residue or brewer's grain) in the feed were 32.4, 22.1, and 15.1%, respectively. The milk fat, protein, and lactose contents did not differ among the milks from farms with different feeding systems. Fatty acids with chain lengths of less than C16 and saturated fatty acids were present at higher concentrations in the milks from the GS and MS farms than in the milk from the BP farms; conversely, fatty acids with chain lengths greater than C18 and unsaturated fatty acids (UFA), including mono- (MUFA) and polyunsaturated fatty acids (PUFA), were present at higher concentrations in the milks from the BP farms than in the milks from the GS farms. No significant differences were detected in milk flavor, evaluated as sweetness, body, texture, aftertaste, and palatability, between the milks from the farms with different feeding systems. The proportion of BP in the cow's diet was positively correlated with the concentrations of fatty acids with chain lengths greater than C18 and with UFA, MUFA, and PUFA. In contrast, the proportion of GS in the diet was positively associated with the levels of milk fat, protein, fatty acids with chain lengths less than C16, and SFA. The MUFA, PUFA, UFA, and fatty acids with chain lengths greater than C18 were not associated with any of the milk flavors. These results suggest the regional differences in feeding systems contribute to the differences in the fatty acid compositions of milk at the farm level. However, these differences do not influence the flavor of pasteurized milk. Thus, more specific feed profiles will be required to provide a specific regional flavor to pasteurized milk.     

Effect of thermal processing on available lysine,thiamine and riboflavin content in soymilk

Soymilk was heated over a range of temperatures (90–140°C) and times (0–6 h). The available lysine, thiamine and riboflavin content of the soymilk samples were determined. There was no significant change in available lysine during a 3 h heating period at 95°C. At elevated temperatures of 120 and 140°C, optimum heat processed soymilk gave higher measured values of available lysine than did soymilk processed at 95°C. Prolonged heating at 120 and 140°C caused a decline in available lysine. Kinetic data on the thermal degradation of thiamine and riboflavin in soymilk were fitted with first-order kinetics and the kinetic parameters were determined. © 1998 SCI.     

Chemical composition and nutritive value of spray dried permeate powder

Reconstituted skimmed milk (10% TS) was ultrafiltered, and the permeate was concentrated threefold by reverse osmosis and then spray dried at different temperatures (145–195° C). The drying conditions had no effect on the moisture content or the major constituents of permeate powder. The powder was mainly lactose (85%) with 6.35460% ash. A small percentage of the lactose in the permeate powder was present as a-lactose. Sodium, potassium and citrate were present in high concentrations nearly equivalent to their average percentage in skimmed milk. The calcium, magnesium and inorganic phosphorus contents of permeate powder were also determined. The thiamine, riboflavin and niacin contents of permeate powder averaged 0.445, 0.947 and 0.729 mg/100 g respectively. The drying temperatures had no effect on the vitamin contents of the powder. The permeate powder had average Fe, Zn, Mn and Cu contents of 94.7, 21.1, 3.1 and 9.5 Fg/100 g respectively.     

Vitamin profiles of kefirs made from milks of different species

Kefirs were produced under laboratory conditions using 10 different kefir grain cultures from different households, and reconstituted cow, ewe, goat and mare milk as substrates. The base milks and corresponding kefirs were examined for their content of water-soluble vitamins and orotic acid. On average, enrichment of vitamin concentration of>20% was observed with thiamine (only ewe milk kefirs), pyridoxine (kefirs from all milk species except cow milk), and folic acid (kefirs from all milk species except mare milk). Orotic acid content was reduced during fermentation throughout.     

Age gelation in UHT-processed reconstituted concentrated skim milk

UHT reconstituted concentrated skim milks made from high-heat powder had considerably longer gelation times than those made from medium- or low-heat powders. Addition of hexametaphosphate to the concentrated milk before UHT processing markedly delayed the onset of gelation during storage. Sediment formation was greatest in the UHT concentrated skim milk made using high-heat powder followed by samples made using medium- and low-heat powders, respectively. The extent of proteolysis, as measured by 12% TCA-soluble amino groups, increased at a faster rate in the UHT milks stored at 40°C than in those stored at 22°C but decreased with increasing heat treatment of the milk prior to powder manufacture. The electrophoretic patterns of samples stored at 22°C clearly showed the breakdown of β-casein with a corresponding increase in slower moving bands, presumably γ-casein and proteose-peptone components. However, storage of samples at 40°C resulted in diffused 'blurred' protein patterns with some protein material not entering the resolving gel. At 22°C there was some evidence of proteolysis but no evidence of high molecular weight polymer formation, while at 40°C both proteolysis and high molecular weight polymer formation increased with storage time. It appeared that both physico-chemical and proteolytic processes play some part in the mechanism of gelation in UHT reconstituted concentrated skim milk.     

Deterioration of protein fraction by Maillard reaction in dietetic milks.

The development of the Maillard reaction in pasteurized, UHT and in-bottle sterilized dietetic milks was studied. In these products damage caused by heat treatments could increase as a result either of the addition of various ingredients or of manufacturing processes that alter their content of reducing carbohydrates. Protein damage was evaluated by measuring furosine by reversed-phase ion-paired HPLC. The levels of furosine detected made it possible to assess the amounts of biologically unavailable lysine. In all milks analysed blocked lysine values were < 340-350 mg/g total lysine, the level at which lysine becomes the limiting amino acid in milk. Pasteurized dietetic milks had levels of blocked lysine similar to that in ordinary pasteurized cows' milk. In some UHT and in-bottle sterilized dietetic milks their different composition resulted in an increase in the blocked lysine content. In some in-bottle sterilized milks, protein damage greatly reduces the beneficial effects of milk as a dietary supplement. Lactose-free milks, which are more susceptible to protein deterioration because of their higher content of reducing carbohydrates, were also analysed after storage at 20 degrees C and at < or = 4 degrees C. At the end of their recommended storage times, they contained limited amounts of blocked lysine only if they had been stored at < or = 4 degrees C.     

The effect of high pressure-low temperature treatment on physicochemical properties in milk

This study was carried out to investigate the effect of high pressure-low temperature (HPLT) treatment on physicochemical properties and nutrients in milk. The milk was treated at 200 MPa and −4°C for 10, 20, and 30 min. Protease and lipase activities of HPLT-treated milk were highly inactivated compared with that of raw milk. Among time treatments, the 30-min treatment showed the lowest activities compared with others. Absorbance of thiobarbituric acid increased with time in HLPT-treated milks; however, no difference was observed between the raw milk and milk treated for 10 min. The concentrations of short-chain fatty acids except C₄ in HPLT-treated milks increased with time. The total free amino acids in HPLT-treated milks were greater than that of the raw milk for the 30-min treatment. l-Ascorbic acid, niacin, and riboflavin in HPLT-treated milks were significantly lower compared with concentrations in raw milk. For color, the L-value of HPLT-treated milks was significantly lower than that of the raw milk; however, there was no difference in the a-value for 10 min and in the b-value at 20 min between the raw milk and the HPLT-treated milks.     

Age of Ultrafiltered Fresh Farm Milk and Effect on Quality

Nonultrafiltered fresh whole raw and heated milks and their retentates concentrated by ultrafiltration to 2.07:1 volume concentration ratio were stored at 4.5 and −20°C and periodically scored for flavor quality.Nonultrafiltered whole raw milks were unclean, fermented, and rancid after 4 to 5 d. Nonultrafiltered heated milks over a 7 to 8-d period developed strong oxidized flavors. Milk retentates produced at 54°C for 120 min showed little or no flavor deterioration after 7 to 8 d at 4.5°C. In the same period at 4.5°C, raw milks from four trials showed 20 defects, heated milks 11 defects and 2.07:1 retentates 2 defects. Milks and retentates held frozen at −20°C for 2 mo showed greater deterioration than split samples held at 4.5°C, but whole milk retentates ultrafiltered to approximately 2:1 volume concentration ratio and stored frozen for 2 mo still displayed good to very good flavor.Thiobarbituric acid values of milks and retentates of ultrafiltration held 4 d at 4.5°C confirmed the presence of strong oxidized flavor in nonultrafiltered heated milks and its virtual absence in whole milk retentates.     

Effect of roasting on some nutrients of hazelnuts (Corylus Avellena L.)

Changes in total amino acid composition, thiamine and riboflavin contents, peroxide value and free fatty acid contents were determined in roasted Giresun and Akçakoca hazelnuts. The results showed that roasting significantly affected peroxide value, free fatty acids, thiamine, riboflavine and total amino acid composition of Akçakoca and Giresun hazelnuts. Riboflavin level decreased by almost 30% in Akçakoca hazelnuts and 18% in Giresun hazelnuts. Above 120°C, more than 50% of thiamine was lost. Amino acid levels in Akçakoca and Giresun hazelnuts generally decreased as the roasting temperature increased. Lysine diminished <6% in samples of roasted Giresun hazelnuts. In Akçakoca hazelnuts, a higher lysine loss was observed (31%) in the sample roasted at 126°C for 45 min.     

Production and evaluation of some physicochemical parameters of peanut milk yoghurt

The peanut milk for yoghurt production was prepared by fortifying peanut milk (∼12 g/100 g total solids) with 4 g/100 g skimmed milk powder. The final product was subjected to physicochemical analysis using cow milk yoghurt (CMY) as a control throughout the study. Peanut milk yoghurt (PMY) had higher protein content, fat, water holding capacity and lower susceptibility to Syneresis than CMY. PMY had lower lactose level (1.73 g/100 ml) compared to CMY (4.93 g/100 ml). Generally both PMY and CMY had high mineral composition and contained high amounts of essential amino acids. PMY also contained a higher proportion of unsaturated fatty acids than saturated fatty acids as compared to CMY. Therefore, in terms of fatty acid composition, PMY could be considered to be more health promoting than CMY. Sensory evaluation revealed that though PMY had better sensory texture scores than CMY, its sensory appearance, flavor and overall acceptability scores were lower than those of CMY.     

The microstructure of set-style, natural yogurt made by substituting microparticulate whey protein for milk fat

The effect of a protein based fat substitute (Simplesse® 100) incorporated at a 1.5% level (w/w) in set-style yogurt on its microstructure, syneresis and firmness was compared with the effect of anhydrous milk fat (AMF) used at the same concentration. The fat substitute was used in both commercial forms available, ie, as a dry or a wet ingredient. The yogurt bases consisted of reconstituted skimmed milk powder including the added ingredients and contained 14.3–15.5% total solids. Electron microscopy revealed that homogenization of AMF produced fat globules which interacted with milk proteins present in the yogurt base and thus the fat became an integral part of the yogurt microstructure. Similar integration was observed with the fat substitute, the particles of which (0.1–3 μm in diameter) were found to be parts of the casein micelle chains or spanned adjacent chains. These chains were found to be somewhat shorter (no statistical assessment was carried out) in the yogurts made with the fat substitute in wet or dry forms than in the yogurt made with AMF. Yogurts with the fat substitute were softer than the yogurts containing AMF, although their composition was similar except for the fat which was replaced with the fat substitute .     

Flavor and flavor chemistry differences among milks processed by high-temperature,short-time pasteurization or ultra-pasteurization

Typical high-temperature, short-time (HTST) pasteurization encompasses a lower heat treatment and shorter refrigerated shelf life compared with ultra-pasteurization (UP) achieved by direct steam injection (DSI-UP) or indirect heat (IND-UP). A greater understanding of the effect of different heat treatments on flavor and flavor chemistry of milk is required to characterize, understand, and identify the sources of flavors. The objective of this study was to determine the differences in the flavor and volatile compound profiles of milk subjected to HTST, DSI-UP, or IND-UP using sensory and instrumental techniques. Raw skim and raw standardized 2% fat milks (50 L each) were processed in triplicate and pasteurized at 78°C for 15 s (HTST) or 140°C for 2.3 s by DSI-UP or IND-UP. Milks were cooled and stored at 4°C, then analyzed at d 0, 3, 7, and 14. Sensory attributes were determined using a trained panel, and aroma active compounds were evaluated by solid-phase micro-extraction or stir bar sorptive extraction followed by gas chromatography-mass spectrometry, gas chromatography-olfactometry, and gas chromatography-triple quad mass spectrometry. The UP milks had distinct cooked and sulfur flavors compared with HTST milks. The HTST milks had less diversity in aroma active compounds compared with UP milks. Flavor intensity of all milks decreased by d 14 of storage. Aroma active compound profiles were affected by heat treatment and storage time in both skim and 2% milk. High-impact aroma active compounds were hydrogen sulfide, dimethyl trisulfide, and methional in DSI-UP and 2 and 3-methylbutanal, furfural, 2-heptanone, 2-acetyl-1-pyrroline, 2-aminoacetophenone, benzaldehyde, and dimethyl sulfide in IND-UP. These results provide a foundation knowledge of the effect of heat treatments on flavor development and differences in sensory quality of UP milks.     

Buffalo vs. cow milk fat globules: Size distribution,zeta-potential,compositions in total fatty acids and in polar lipids from the milk fat globule membrane

Although buffalo milk is the second most produced milk in the world, and of primary nutritional importance in various parts of the world, few studies have focused on the physicochemical properties of buffalo milk fat globules. This study is a comparative analysis of buffalo and cow milk fat globules. The larger size of buffalo fat globules, 5 vs. 3.5 μm, was related to the higher amount of fat in the buffalo milks: 73.4 ± 9.9 vs. 41.3 ± 3.7 g/kg for cow milk. Buffalo milks contained significantly lower amount of polar lipids expressed per gram of lipids (0.26% vs. 0.36%), but significantly higher amount of polar lipids per litre of milk (+26%). Buffalo and cow milk fat globule membranes contain the same classes of polar lipids; phosphatidylethanolamine, sphingomyelin (SM) and phosphatidylcholine (PC) being the main constituents. A significant higher percentage of PC and lower percentage of SM were found for buffalo milks. The fatty acid analysis revealed that saturated fatty acids, mainly palmitic acid, trans fatty acids, linolenic acid (ω3) and conjugated linolenic acid were higher in buffalo milk than in cow milk. Such results will contribute to the improvement of the quality of buffalo milk-based dairy products.     

Relationship of Protease Activity to Shelf-Life of Skim and Whole Milk

This study was to investigate causes of a possible difference in shelf-life of pasteurized skim milk and whole milk. Samples of skim and whole milk were obtained the day of processing, in 235 ml containers, from commercial dairies throughout South Carolina. They were stored at 4.5°C for 0,4,8,10,12,14, and 16 days; 7°C for 0,4,6,8,10, and 12 days; and 10°C for 0,1,2,3,4,5, and 6 days. On each sampling day milks were tested for coliform count, psychrotrophic count, flavor score, and relative protease activity. The shelf-life of skim milk was significantly less than that of whole milk when both were stored at 4.5°C and 7°C, but not at 10 C. Bacteria counts were not significantly different; thus, they were of no predictive value as anticipated changes in flavor score. Relationship between flavor score and relative protease activity of skim and whole milk was linear. Also, relative protease activity was significantly higher in skim milk as compared to whole milk stored at 4.5 and 7° C. Therefore, a higher protease activity in skim milk may account partially for its decreased shelf-life.