Microstructure and rheological properties of whipped cream as affected by heat treatment and addition of stabilizer

Whipping cream, 36% fat, was processed at 75°C for 16 s (high-temperature short time, HTST), and 140°C for 4 s, (ultra-high temperature, UHT) with and without added stabilizer. Following heat treatment and chilling for 24 h (5°C), cream samples were whipped to maximum overrun. Structural properties were assessed through low-temperature scanning electron microscopy (LTSEM) and dynamic oscillatory testing, using a controlled stress rheometer, immediately after the cream was whipped, and again after the foam was stored for 24 h at 5°C. No differences between fresh foam treatments were observed. However, aged foams exhibited changes in microstructure because of destabilization of the foam. Differences between aged foams resulted from the addition of stabilizers and the choice of heat treatment. Microstructural differences correlated well with measured changes in rheological properties.     

Effect of seasonal variation on the properties of whipping cream,soft cheese and skim milk powder in the UK

Whipping cream, skim milk powder and soft cheese were produced throughout the year. Whipping cream manufactured in spring and winter produced significantly higher overrun and better serum stability, and whipping time was related to buffering capacity of raw milk. Heat stability of reconstituted skim milk powder (RSMP) at 9% total solids (TS) was greater in summer and autumn, and >25% TS throughout the year. It was positively related to the protein content of raw milk, but negatively with fat. In contrast to other dairy products, no significant effect of season on the properties of soft cheese was found.     

Influence of whipping temperature on the whipping properties and rheological characteristics of whipped cream

The effects of whipping temperature (5 to 15°C) on the whipping (whipping time and overrun) and rheological properties of whipped cream were studied. Fat globule aggregation (aggregation ratio of fat globules and serum viscosity) and air bubble factors (overrun, diameter, and surface area) were measured to investigate the mechanism of whipping. Whipping time, overrun, and bubble diameters decreased with increasing temperature, with the exception of bubble size at 15°C. The aggregation ratio of fat globules tended to increase with increasing temperature. Changes in hardness and bubble size during storage were relatively small at higher temperatures (12.5 and 15°C). Changes in overrun during storage were relatively small in the middle temperature range (7.5 to 12.5°C). From the results, the temperature range of 7.5 to 12.5°C is recommended for making whipped creams with a good texture, and a specific temperature should be decided when taking into account the preferred overrun. The correlation between the whipped cream strain hardness and serum viscosity was high (R² = 0.906) and persisted throughout the temperature range tested (5 to 15°C). A similar result was obtained at a different whipping speed (140 rpm). The multiple regression analysis in the range of 5 to 12.5°C indicated a high correlation (R² = 0.946) in which a dependent variable was the storage modulus of whipped cream and independent variables were bubble surface area and serum viscosity. Therefore, fat aggregation and air bubble properties are important factors in the development of cream hardness. The results of this study suggest that whipping temperature influences fat globule aggregation and the properties of air bubbles in whipped cream, which alters its rheological properties.     

Producing ice cream using a substantial amount of juice from kiwifruit with green,gold or red flesh

Ice cream prepared using a substantial amount of juice from kiwifruit with green, gold or red flesh may have consumer appeal, through the combination of kiwifruit's unique color, natural flavor and health-promoting constituents. The aqueous fractions from purees of kiwifruit with green, gold and red flesh (AFKWs) were added at 49% v/v to a basic low-fat ice cream mix that contained no commercial flavoring and coloring agents. The resultant ice creams were subjected to comparative product evaluation (e.g. overrun, melting behavior and rheological properties) and chemical analyses of bioactives (e.g. total extractable polyphenol content (TEPC), vitamin C, antioxidant capacity, polyphenol (PP) and carotenoid composition). Results revealed that both the pH pre-adjustment and pre-heating of the AFKW played critical roles in ice cream making. The ice creams retained the PP and vitamin C contents as well as natural color flavor of the kiwifruit used. The rheological properties of all ice creams showed non-Newtonian flow behavior, and the storage modulus G′ decreased in the same pattern following the order of green > gold > red. The melting rate, overrun and vitamin C content of the ice cream with green AFKW were the fastest, lowest and least, respectively. The TEPC and antioxidant capacity in the ice cream with red AFKW were the highest. The amounts of PPs and vitamin C were encouragingly high. Health beneficial compounds, dimethyl-caffeic acid hexoside, caffeic acid derivatives, protocatechuic acid, syringic acid, salicylic acid/ο-coumaric acid, lutein and beta-carotene, were detected in the final products. Thus, there are commercial possibilities for using AFKW which should be further evaluated.     

Influence of Cape gooseberry (Physalis peruviana L.) addition on the chemical and sensory characteristics and mineral concentrations of ice cream

In this research, the influence of Cape gooseberry (CG) addition at different concentrations (5, 10 and 15%) on the physical, chemical and sensory properties and mineral contents of ice cream was investigated. The increment of CG concentration caused the decrease of fat, protein, pH and overrun values in ice cream, on the contrary it increased the total solid, ash, titratable acidity, viscosity values and first dripping and complete melting times. S contents of ice creams significantly increased with the CG addition. Moreover, CG increased K, and Na concentrations of ice cream, while lowered Ca and P contents. Mg contents of ice creams didn't change with CG addition (P > 0.05). Fe, Zn, Mn and Ni were determined as minor elements in ice cream samples and a significant increase was observed in Fe, Zn and Mn values (P < 0.05). The addition of CG did not affect Ni content of ice creams. The sensory results indicated that the ice cream containing 15% CG was the highest-scored by the panelists.     

High hydrostatic pressure modification of whey protein concentrate for use in low-fat whipping cream improves foaming properties

Whey is the inevitable by-product of cheese production. Whey can be incorporated into a variety of foods, but little has been done to investigate its suitability in whipping cream. The objective of this work was to evaluate the foaming properties of selected low-fat whipping cream formulations containing whey protein concentrate (WPC) that did or did not undergo high hydrostatic pressure (HHP) treatment. Fresh whey was concentrated by ultrafiltration, pasteurized, and standardized to 8.23% total solids and treated with HHP at 300 MPa for 15 min. Viscosity, overrun, and foam stability were determined to assess foaming properties. Sensory evaluation was conducted with 57 panelists using a duo-trio difference test. The optimal whipping time for the selected formulations was 3 min. Whipping cream containing untreated WPC and HHP-treated WPC resulted in greater overrun and foam stability than the control whipping cream without WPC. Panelists distinguished a difference between whipping cream containing untreated WPC and whipping cream containing HHP-treated WPC. High hydrostatic pressure-treated WPC can improve the foaming properties of low-fat whipping cream, which may justify expansion of the use of whey in whipping cream and application of HHP technology in the dairy industry.     

Effect of whey protein concentrate addition on the physical properties of homogenized sweetened dairy creams

The influence on their whipping properties of homogenization at first and second stage pressures of 3.5/1.5 MPa and addition of whey protein concentrate (WPC) powder at three different (0.7, 1.4, and 2.1 wt percentage) concentrations to sweetened and homogenized creams was studied. Homogenization of cream significantly decreased maximum overrun and made the foam microstructure less open, while increasing whipping time, cream and foam lightness (Hunter L -value) and apparent viscosity. It also resulted in a less elastic foam structure with an increased drainage. Addition of WPC decreased the amount of maximum overrun, foam drainage and its lightness in parallel with developing a more compact microstructure. It increased the whipping time, apparent viscosity of unwhipped creams and foams, and resulted in a less elastic foam structure. The apparent viscosity of whipped cream with 2.1 wt percentage WPC, however, was lower than that of whipped cream with 1.4 wt percentage WPC, due most probably to the start up of gel formation at 2.1% WPC concentration in sweetened cream when it was sheared. Fresh foam whipped from sweetened cream with 2.1 wt percentage WPC also tended to have a slightly but not statistically significant lower elastic modulus (G') than fresh foam whipped from sweetened cream with 1.4 wt percentage WPC. This concentration can be considered as the critical value for gel formation in sweetened creams enriched by whey proteins when sheared. This study indicated the potential of WPC powder for reducing foam drainage from whipped homogenized sweetened cream.     

Native milk fat globule size and its influence on whipping properties

The objective of this study was to investigate the influence of native milk fat globule size on the aeration of high fat dairy products with regard to maximum firmness time, gas inclusion and foam stability. The results showed that whipping time to maximum firmness was inversely proportional to mean fat globule size for both unhomogenised and slightly homogenised (2 MPa) creams. Additionally, increasing native mean fat globule size of the creams resulted in increased overrun. No significant differences in serum drainage were found between creams with different native milk fat globule size. Furthermore, when creams with native large mean fat globules were homogenised, the results showed that the maximum firmness time was in accordance with the mean fat globule size of non-aggregated creams. In the present study, cream fractionation was achieved by creaming or in a cost effective and fast manner using a modified centrifugal separator.     

搅打稀奶油的乳液特征和打发性能研究

为了对搅打稀奶油的科学应用提供参考,以19款市售代表性搅打稀奶油（常温型、冷藏型和冷冻型产品）为研究对象,通过分析乳液的离心乳析率、黏度、粒径和微观结构研究其乳液的质量,通过分析打发时间、起泡率、泄漏率和裱花性能研究其打发性能。结果显示：常温型产品的离心乳析率为22.17%～32.68%,显著高于冷藏型产品的离心乳析率(1.36%～13.09%)和冷冻型产品的离心乳析率(2.97%～12.87%);常温型和冷藏型产品的黏度、粒径分布特征接近,呈流动性较好且脂肪球分布较均匀的乳液,而冷冻型产品相对黏稠且乳液中无明显脂肪球结构;常温型产品和冷藏型产品的打发时间在13244～291.28 s之间（只有1款冷藏型产品打发时间为79.49 s）,起泡率在111.49%～202.50%之间（只有2款冷藏型产品起泡率分别为92.30%、328.25%）,部分有泡沫泄漏,裱花维持能力较弱;而冷冻型产品打发时间为89.91～158.52 s,起泡率在240.39%～27815%,无泡沫泄漏,裱花维持能力强。综合而言,常温型搅打稀奶油的乳液相对不稳定,打发性能与冷藏型搅打稀奶油接近,而冷冻型搅打稀奶油的打发性能最强。     

Proteolysis and storage stability of UHT milk produced in Turkey

The effect of raw milk quality (total and psychrotrophic bacterial and somatic cell counts, proteinase and plasmin activity) and UHT temperature (145 or 150 °C for 4 s) on proteolysis in UHT milk processed by a direct (steam-injection) system was investigated during storage at 25 °C for 180 d. High proteinase activity was measured in low-quality raw milk, which had high somatic cell count, bacterial count and plasmin activity. The levels of 12% trichloroacetic acid–soluble and pH 4.6-soluble nitrogen in all milk samples increased during storage, and samples produced from low-quality milk at the lower UHT temperature (145 °C) showed the highest values. Bitterness in UHT milk processed from low-quality milk at 145 °C increased during storage; gelation occurred in that milk after 150 d. The RP-HPLC profiles of pH 4.6-soluble fraction of the UHT milk samples produced at 150 °C showed quite small number of peaks after 180 d of storage. Sterilization at 150 °C extended the shelf-life of the UHT milk by reducing proteolysis, gelation and bitterness.     

均质压力对UHT搅打稀奶油品质的影响

以新鲜稀奶油为主要原料,考察了不同的均质压力对UHT搅打稀奶油的脂肪球粒径、流变学特性、搅打特性的影响,分析了各评价指标之间的相关性。结果表明,UHT搅打稀奶油最适均质压力范围为3～5 MPa;随着均质压力的增大(1～9 MPa),脂肪球粒径减小,但打发成型所需时间增加;在α=0.01水平上,粒径与搅打时间、起泡率显著相关;在α=0.05水平上搅打时间与起泡率显著相关。     

Whipping properties of recombined,additive-free creams

There is increasing industrial interest in the use of the milkfat globule membrane as a food ingredient. The objective of this research was to determine whether the aerosol whipping performance of cream separated into butter and buttermilk, and then recombined, would perform in a manner similar to untreated cream. Churning of cream tempered to different solid fat contents was used to separate butter from buttermilk, which were then recombined at the same ratios as the initial extraction yield, or with 25% extra buttermilk. Differences in milkfat globule size distributions among the recombined creams were apparent; however, their whipping behavior and overrun were similar. Importantly, all recombined creams did not yield properties similar to the original cream, indicating that the unique native milkfat globule membrane structure plays a role in cream performance well beyond its simple presence.     

黄油-代可可脂基奶油生产工艺优化及其晶型形成分析

在分析油脂用量对黄油-代可可脂基奶油品质影响的基础上,通过正交试验研究油脂用量、黄油-代可可脂质量比和均质压力对奶油搅打性能、质构特性、脂肪球部分聚结率、结晶特性等的影响。结果表明,在油脂用量30%、黄油-代可可脂质量比2∶3、均质压力60?MPa的条件下,能保证脂肪部分聚结的发生,并保持搅打稀奶油较好的感官特性、起泡性和结晶特性。60?MPa的均质压力保证了体系的稳定性,使大量游离脂肪球产生从而促进脂肪部分聚结。晶型形成分析结果表明,在优化条件下,原料乳浊液X-射线衍射峰峰形由较宽、较尖锐变为峰形适中均匀,适宜搅打稀奶油的β’晶型晶体明显增多,搅打稀奶油乳浊液在低温条件下发生脂肪结晶,表现为脂肪晶体尺寸增大。     

Design and Operation of an Experimental Cheese Processor

The design and operating characteristics of a horizontal cheese cooker, which has a maximum capacity of 4 kg raw material per batch, are described. Considerations for processor design included comparability of experimental results with large commercial units, limitation of batch size to reduce raw material required, accommodation of a wide range of process variables, “sanitary” design, ease of operation, ease and speed of cleaning, and pressurization if desired. A screw speed of 70 rpm, cook temperature of 75 to 82°C, and total residence time of 4 min produced a process cheese of good melting and slicing characteristics. Detailed fabrication drawings may be obtained by writing to the authors.     

Survival of Lactobacillus johnsonii La1 and influence of its addition in retail-manufactured ice cream produced with different sugar and fat concentrations

After several studies have proved the benefits deriving from the ingestion of probiotic bacteria, various dairy products containing lactobacilli and bifidobacteria cultures have been formulated in recent years. A 2⁴ full factorial experimental design was applied to verify the effects of Lactobacillus johnsonii La1 addition in retail-manufactured ice cream stored at two different freezing temperatures and containing two different levels of sugar and fat. Both fresh and frozen–thawed La1 cells underwent preliminary resistance tests to bile, antibiotics, SDS, and acidity. La1 strain proved to be highly resistant to most of stress factors, thus excluding the possibility to find evidence of cell sublethal injuries caused by freezing. When the microorganism was added to ice cream mixes in the quantity of 10⁷ cfu g⁻¹, it did not modify the overrun and firmness of the finished product. Regardless of formulation, no count decay of La1 cells was observed in ice cream stored for up to 8 months.     

Ultra high pressure homogenization of soymilk: Microbiological,physicochemical and microstructural characteristics

The effect of ultra high pressure homogenization (UHPH) at 200 and 300 MPa on soymilk was studied. A soymilk base product (BP) and ultra high temperature (UHT) treated soymilk were compared with UHPH treated soymilk. UHPH at 200 and 300 MPa reduced initial counts, spores and enterobacteria counts. Particle size analysis evidenced the intense reduction of particle size caused by UHPH, although the formation of aggregates was detected at 300 MPa. Colour differences between UHPH and BP or UHT soymilks were found. Treated soymilk (300 MPa) showed the lowest values of L¹, a¹ and b¹ coordinates. UHPH processed samples were more stable (showed less particle settling) than BP and UHT soymilks and these differences were also observed at days 30 and 60 of storage at 4 °C. Differential scanning calorimetry analysis indicated that soymilk proteins were partially denatured by 200 MPa, whereas UHPH treatment at 300 MPa showed the same extent of denaturation as UHT soymilk. Images of transmission electron microscopy showed the distribution and general characteristics of the colloidal particles and structures of UHPH, BP and UHT which were generally in accordance with the physicochemical parameters studied.     

Relating consumer and trained panels’ discriminative sensitivities using vanilla flavored ice cream as a medium

This research investigated the possibility of uncovering a relationship between the sensitivities of trained and consumer panels in three experiments. In Experiment I, five studies were conducted using vanilla flavored ice cream. In each study, two ice cream samples differing in formulation and/or their manufacturing process were used. They were compared by both panels using same–different tests with sureness judgments (degree of difference methodology). Using the appropriate probabilistic Thurstonian model, d′ values, a measure of the underlying sensory difference perceived between the products, were calculated and the underlying relationship between the two panels’ sensitivities uncovered. An additional study was then conducted (Experiment II). A new pair of ice creams differing in fat content was first evaluated by the trained panel. Based on the estimated d′ value (trained panel’s measured d′ = 2.69), the corresponding consumer d′ value was predicted using the relationship uncovered in Part I (consumer panel’s predicted d′ = 1.54). The same pair of ice creams was then evaluated by the consumer panel. The measured d′ value for the consumers was almost identical to that predicted by the uncovered relationship (consumer panel’s measured d′ = 1.56). Along with the discrimination component of these studies, paired preference tests were conducted (Experiment III) in order to study a link between perceived difference and expressed preference. The results give an indication of when a perceived difference might start translating into a change in acceptability of the original product. These results indicate the potential of such an approach to predict consumers’ perceptions from an in-house semi-trained or trained panel, providing a useful predictive tool and a means of reducing repetitive and costly consumer testing.     

搅打稀奶油品质及其影响因素的研究进展

搅打稀奶油是一类可搅打起泡的水包油乳液。作为重要的食品工业原料,搅打稀奶油可作为呈味物质赋予食品良好的感官特性,应用前景广阔。本文首先介绍搅打稀奶油贮藏期内常见的失稳作用,包括乳析、聚集、聚结、部分聚结及奥氏熟化,并阐述界面特性及脂肪球间的交互作如何影响搅打稀奶油的稳定性;其次介绍搅打稀奶油的搅打过程,阐述结晶特性、界面特性和液相蛋白特性如何影响搅打特性。本文可为搅打稀奶油产品的工业化生产提供一定的理论指导。     

麦芽糊精与复配糖比例对降糖植脂奶油搅打性能和品质的影响

本文以麦芽糊精和复配糖（葡萄糖、白砂糖和淀粉糖浆组成）为原料制备总糖浓度为18.60 wt%的降糖植脂奶油,研究了麦芽糊精与复配糖不同的比例（0:20~9:11）对降糖植脂奶油搅打性能和品质的影响。比较了植脂奶油的水分分布、界面蛋白浓度、脂肪部分聚结率、最佳搅打时间、搅打起泡率、硬度、感官评价、储藏稳定性等指标。研究发现,当麦芽糊精与复配糖比例从0:20增加至3:17,植脂奶油的界面蛋白浓度和硬度明显增加,储藏稳定性提高,感官评价稍有降低;进一步增加麦芽糊精与复配糖比例至9:11时,植脂奶油的脂肪部分聚结率、搅打起泡率、感官评价和储藏稳定性明显降低,搅打性能和品质均较差。综合考虑搅打性能和品质的影响,当麦芽糊精与复配糖的比例分别在3:17和5:15时,降糖植脂奶油的搅打起泡率为353.3%和342.2%,硬度为325.6 g和329.1 g,横截面光滑,此时搅打性能和品质更佳。     

Effect of ultra high temperature (UHT) treatment on coffee brew stability

In this work, the influence of an Ultra High Temperature (UHT) treatment on chemical and sensory composition of Arabica coffee brews for a longer shelf-life has been studied. A temperature of 120 °C for 2 s allows to obtain a microbiologically safe coffee brew, good valued from the sensory point of view. The behavior of the UHT vs non UHT treated coffee brew was followed throughout 120 days of storage at 4 °C. The UHT treatment keeps the typical acidity of the brews longer, delaying and softening the pH decrease and the development of sourness, which is one of the main causes for the rejection of stored coffee brews. The UHT treatment hardly affects the concentrations of caffeine and trigonelline, and of some phenolic compounds such as 5-caffeoylquinic (5-CQA), caffeic or ferulic acids. Sixteen key odorants and staling volatiles were analyzed by HS–GC–MS and lower changes were observed in the UHT treated coffee brew throughout storage. Higher DPPH scavenging activity was observed in the UHT treated coffee brew from days 60 to 120. In conclusion, the application of an UHT treatment is proposed to extend the shelf-life (up to 60 days) of stored coffee brews.