Sensory characteristics of human milk: Association between mothers' diet and milk for bitter taste

It is unknown how consumption of bitter foods and beverages in the maternal diet influences sensory properties of fresh human milk. The aims of this study were (1) to determine the sensory characteristics of fresh human fore and hind milk, (2) to establish relationships between sensory properties and composition of fresh human milk, and (3) to assess the relationship between bitterness of the maternal diet and human milk. Twenty-two lactating mothers generated sensory terms to describe perception of their milk and received training on sensory attribute intensity rating. Mothers kept a 24-h food diary followed by a sensory self-assessment of their fore and hind milks. The odor of human fresh milk was described as neutral, creamy, and sweet, taste as sweet and bitter, and mouthfeel as thin, watery, smooth, and fatty. Sweetness was equivalent to 1.53 g of sucrose/100 mL and was not significantly different between fore and hind milk. Fore milk was significantly less creamy, less fatty, thinner, more watery, and lower in vanilla flavor intensity than hind milk. Carbohydrate content of human milk was positively correlated with sweetness and glutamic acid content with umami. The bitterness of the diet consumed 24 h before lactation was moderately positively correlated with bitterness of fore milk, but not hind milk. We conclude that the consumption of bitter foods may influence the bitterness of human fore milk, which may be another way for?breastfed children to learn to accept bitter vegetables and, hence, develop healthier food preferences.     

A 100-Year Review: Sensory analysis of milk

Evaluation of the sensory characteristics of food products has been, and will continue to be, the ultimate method for evaluating product quality. Sensory quality is a parameter that can be evaluated only by humans and consists of a series of tests or tools that can be applied objectively or subjectively within the constructs of carefully selected testing procedures and parameters. Depending on the chosen test, evaluators are able to probe areas of interest that are intrinsic product attributes (e.g., flavor profiles and off-flavors) as well as extrinsic measures (e.g., market penetration and consumer perception). This review outlines the literature pertaining to relevant testing procedures and studies of the history of sensory analysis of fluid milk. In addition, evaluation methods outside of traditional sensory techniques and future outlooks on the subject of sensory analysis of fluid milk are explored and presented.     

Sensory evaluation of ovine milk yoghurt with inulin addition

The purpose of this study was to elaborate prebiotic yoghurt using ovine milk and different inulin concentrations (0, 2 and 6%). Samples were submitted to laboratory analysis and two sensory tests with 100 consumers. The results of apparent viscosity and firmness determined by instrumental analysis of each yoghurt and control differed significantly. Just‐About‐Right showed consistency as the main attribute that varied in treatments. According to penalty analysis, prebiotic yoghurt containing 6% inulin had minor penalties, which indicates its advantage in the quest to better consumer demands. Hence, this treatment demonstrated better results as well as the many prebiotic benefits associated with an adequate fibre amount.     

Sensory evaluations and stability determinations of goat milk containing galactooligosaccharides

The objectives of this study were to evaluate the feasibility of producing goat milk containing galactooligosaccharides (GOS) by β‐galactosidase and to determine the sensory attribute and stability of goat milk containing GOS. The results indicated that the maximum GOS obtained were approximately 13.9% of total sugars at pH 4.5 and temperature 40 °C. The sensory attribute of the obtained GOS was determined using a 5‐point hedonic scale in terms of taste, flavour, appearance and overall acceptability. There were significant increases in taste and overall acceptability of goat milk containing higher GOS concentration when compared to regular goat milk (control). Also, goat milk containing GOS presented a good stability over the acidic conditions. GOS in goat milk were also stable after the high heat treatment and shelf life conditions.     

Sensory and molecular characterisation of human milk odour profiles after maternal fish oil supplementation during pregnancy and breastfeeding

The odourant profile of human milk has been proposed to be modulated by the composition of the maternal diet via the transference of specific food aromas to the milk, such that neonates are exposed to these aromas and are prepared for latter acceptance of specific diets. For that reason the aim of the present study was to investigate whether specific fish oil odour constituents translate into human milk. To achieve this goal, human sensory analyses and qualitative and quantitative instrumental determination of fish oil odourants were performed on the fish oil, as well as on human milk obtained from mothers after long-term fish oil supplementation in comparison to a control group. Sensory and analytical data showed that no statistically significant modification occurred from fish oil intervention.     

Sensory threshold of off-flavors caused by proteolysis and lipolysis in milk

The objective of this study was to determine the sensory threshold of off-flavor caused by lipolysis in 2% fat milk and to establish the relationship between increased proteolytic activity in milk and the detection of bitter off-flavor. Homogenized raw milk was held at room temperature for 100 min to allow the native milk lipase to release free fatty acids from the triglycerides. Low and high lipolysis pasteurized milk containing 2% fat were blended together in varying amounts to create a series of six milks with increasing free fatty acid (FFA) concentration for sensory evaluation. Sensory threshold for lipolysis in 2% fat milk was determined by ascending forced-choice procedure, with a series of triangle tests in four sessions with 25 panelists in each session. The group best estimated threshold was the geometric mean of the individual thresholds within each of four panel sessions. The geometric mean best estimated detection thresholds for off-flavors caused by lipolysis in 2% fat milk carried out by native milk lipases were 0.320, 0.322, 0.351, and 0.316 meq of FFA/kg milk for panels 1 to 4, respectively. One third of the panelists detected an off-flavor at or below 0.250 meq of FFA/kg milk. To establish the relationship between proteolysis and detection of off-flavor in pasteurized skim milk, 2800 ppm of CO2 were added to pasteurized skim milk, and it was stored for 27 d at 6 degrees C. Another portion of the same milk was frozen on d 1 at -40 degrees C for use as a low proteolysis portion of the same milk. Decrease in casein as a percentage of true protein (CN/TP) was used as an index of proteolysis. After 27 d at 6 degrees C the milk had a decrease in CN/TP of 4.76% and a standard plate count of 430 cfu/ml. The novel approach of storing milk at 6 degrees C for 27 d with added CO2 blocked microbial growth but allowed proteolytic degradation by milk enzymes to proceed. Before sensory analysis, CO2 was removed by vacuum from the high proteolysis milk and the low proteolysis milk was given the same heat and vacuum. Two triangle tests were performed to determine whether panelists could detect off-flavors caused by proteolysis in milk. The threshold detection of off-flavor in skim milk produced by the action of native milk proteases was less than a decrease of CN/TP of 4.76%, but this value is probably near the threshold.     

Physico-chemical characterization of phosphate-added skim milk

The addition of potassium phosphate (KH₂PO₄) to milk is a common practice in the dairy industry but the changes resulting from such addition have not been fully elucidated. Physico-chemical changes were evaluated after addition of KH₂PO₄ at concentrations from 0 to 160 mm with or without adjustment of pH. At pH adjusted to 6.8, the addition of phosphate to milk-induced formation of insoluble calcium phosphate salt, decrease in lightness and solubilization of casein molecules. As a result of these biochemical changes, especially at high phosphate concentrations (about 120 mm and more), the formation of large aggregates occurred. At the same time, the amount of water combined with the modified casein strongly increased. When the pH was not adjusted, the same biochemical changes occurred but they were quantitatively lower. In this case, no destabilization of casein micelles occurred.     

人母乳源乳酸菌的筛选、鉴定及益生活性的初步研究

本研究从人母乳中分离乳酸菌。采用透明圈法从产后10³0 d的人母乳样品中筛选到一株产酸能力较强的乳酸菌。对筛选菌株进行形态学观察、生理生化实验及16S r DNA序列鉴定。结果发现,该菌株为革兰氏阳性,短杆状,无芽孢;生理生化特性符合鼠李糖乳杆菌的基本特征;16S r DNA序列及进化树分析进一步确认该菌株为鼠李糖乳杆菌,命名为鼠李糖乳杆菌Z5。在p H3.0的条件下模拟人工胃肠液共消化6 h后该菌存活率仍达90%以上,在0.15 g/L胆盐质量浓度培养6 h,菌株存活率为76.14%;抑菌实验发现,菌株培养液对沙门氏菌及大肠杆菌的生长有明显的抑制作用,抑菌圈直径达20 mm以上。细胞黏附实验发现,该菌株可有效黏附到Caco-2细胞表面,对Caco-2细胞的平均黏附数为7.54×105cfu/m L。从人母乳中获得了这株具有潜在益生性质的鼠李糖乳杆菌,为明确母乳中益生菌的功效及开发新型益生菌产品研究提供了良好的实验材料。      

Sensory stability and oxidation of fish oil enriched milk is affected by milk storage temperature and oil quality

The experiments evaluated the influence of fish oil quality and cold storage temperature on the oxidative stability of milk emulsions containing 1.0% w/w milk fat and 0.5% w/w of either a pure fish oil or a fish oil:rapeseed oil mixture. The results showed that it was possible to produce a pasteurised milk product enriched with the important n-3 PUFA from fish oil with acceptable sensory characteristics if (1) the emulsions were based on a mixture of fish oil and rapeseed oil and (2) the initial peroxide value (PV) of the added oil blend was below 0.5 meq kg⁻¹. The sensory analysis showed a clear distinction between emulsions based on oil with PV 0.1 and 0.5 meq kg⁻¹, whereas the PV and the gas chromatographic (GC) analysis of volatile oxidation products were not sensitive enough to reveal these differences clearly. The GC analyses showed that the onset of formation of the volatiles was earlier with increased storage temperature in the range of 2–9 °C.     

Sensory properties of kishk: comparison of products containing bovine and caprine milk

There is growing consumer interest in fermented milk and in products containing fermented milk because of their nutritional value and healthy image. Kishk, a traditional product of Middle Eastern origin, has been examined with a view to developing its potential for a wider market. Kishk is traditionally made from a dough, containing yogurt, parboiled cracked wheat and salt, which is sun dried then ground to a flour. The flour may be consumed in a variety of ways, but one popular use is in the preparation of a hot, porridge like gruel. This paper describes the sensory profiles of gruel made from 15 samples of kishk and compares them with those of two traditional Scottish oatmeal porridges. Substantial differences were noted between kishk and the oat based products. In addition, there was evidence that the origin of the fermented milk component of the kishk was important. Kishk made from fermented caprine milk was clearly distinguished from that made with yogurt of bovine origin. It was noted that many of the kishk samples were rated highly for bitterness and for cardboard character. Such attributes are believed to be disliked by consumers in the United Kingdom .     

基于人乳脂肪组成的酶法人乳脂肪替代物的构建

为了开发新型高相似性人乳脂肪替代物,依据中国人乳脂肪的脂肪酸组成和甘油三酯结构,以巴沙鱼油、樟树籽仁油、亚麻籽油、微生物油(富含ARA)及DHA藻油(质量比为153.81∶15.16∶62.33∶7.89∶10.81)为原料油脂,以固定化脂肪酶Lipozyme RM为催化剂,在60℃下酯交换反应8 h制备人乳脂肪替代物,测定其脂肪酸、sn-2位脂肪酸及甘油三酯组成及含量,分析其红外光谱图、熔融性质、结晶性质及流变学性能。结果表明,构建的人乳脂肪替代物中链脂肪酸含量为12%、亚油酸和亚麻酸总含量为19.53%且比例约为1∶1.5,ARA含量为1.17%,DHA含量为1.11%,其sn-2位富含棕榈酸(43.10%),结构甘油三酯含量高(58.75%),无反式脂肪酸生成,熔融温度低于人体温度且在20℃下仍能保持18.7%的固体脂肪含量,结晶形态细腻且流变性能优异。制备的人乳脂肪替代物具有应用于婴幼儿配方奶粉、婴幼儿米糊和婴幼儿饼干等各种婴幼儿食品的潜力。     

Purification and characterization of bovine milk fibronectin

Fibronectins were isolated from both bovine colostrum and fresh milk, and they were found to be very similar to plasma fibronectin. The concentration of fibronectin in milk decreased post partum: 30 micrograms/ml after 0 d and 2 micrograms/ml after 7-851 d. No fibronectin could be detected in any brands of ultra heat treated liquid milk on the market (less than or equal to 0.006 micrograms/ml).     

Nitrate-reducing microorganisms in milk products and human milk

The quantitative determination of nitrate-reducing microorganisms in food is important because of their role in the formation of N-nitroso compounds and methemoglobin. The total counts of microorganisms and the counts of nitrate-reducing microorganisms were assayed in various milk products and in human milk by the method of the most probable numbers using nitrate broth medium. The mean value and standard deviation of the nitrate-reducing microorganisms were the following: in pasteurized milk 3.4 +/- 1.1 log/ml (in spring and summer 4.2 +/- 1.1, and in winter 2.8 +/- 0.6 log/ml), in kefir "Tallinn' 2.9 +/- 1.1 log/ml, in fat kefir 2.9 +/- +/- 0.7 log/ml, in sour milk 3.9 +/- 0.5 log/ml, in fresh milk 4.6 +/- 0.6 log/ml and in human milk 2.7 +/- +/- 1.1 log/ml. The amount of nitrate-reducing microorganisms in pasteurized milk of the spring-summer period and in fresh milk was significantly higher than in human milk. The mean count of nitrate-reducing microorganisms in human milk is regarded as a maximum permitted count of these organisms in milk for bottle-fed sucklings. For them and for atrophic gastritis patients pasteurized or fresh milk should be boiled.