Characteristics of biological aerosols in dairy processing plants

The viable aerosol in dairy processing plant environments was characterized by using an Andersen six-stage sieve sampler and a Reuter centrifugal sampler. Artificially introduced Serratia marcescens were detected in the air during drain flooding and after rinsing the floor with a pressured water hose, thus illustrating the ability of a specific microorganism to be disseminated from drains and wet surfaces via physical disruption activities often observed in food plants. Once a high concentration of wet viable aerosol was generated, it took 40 or more min to return to the background level in the absence of forced ventilation or other activity. The greatest reduction in viable particles occurred during the first 10 min. Estimated mean aerosol particle sizes were decreased from approximately 4.6 to 3.2 mu with time lapse. The estimated mean aerosol particle sizes from actual dairy processing plant environments ranged from approximately 4.3 to 5.3 mu. In addition, a more heavily contaminated dairy processing environment contained larger aerosol particles. These results indicate that the RCS sampler will often overestimate the true aerosol concentration in highly contaminated air, because mean particle sizes are over 4 mu in diameter.     

Bulking agents in low calorie frozen dairy desserts

The use of intense sweeteners in the manufacture of low calorie frozen desserts has brought about the need to add bulking agents to replace the sugar omitted in such products. A bulking agent acts as a filler and reproduces the physical properties of sugar, but not its sweetness and caloric content. Careful attention must be paid to combining sweeteners (polyols) with bulking agents in order to regulate the freezing point of the mix, and to restrict the levels to those which do not impart off­flavours or create gastrointestinal distress. Some modifications in the freezing and serving conditions are needed with the addition of bulking agents. The newlmodified bulking agents need to be approved by the regulatory bodies to ensure their safety. There is a need to identify a low or non-caloric bulking agent with little or no laxative effect.     

Structuring dairy systems through high pressure processing

This review highlights the current knowledge on gelation of hydrocolloids induced by high pressure processing (HPP) of dairy products. Pressure-induced gelation of single systems (casein rich, whey protein rich, gelatin, and polysaccharide solutions) as well as rheological and thermo-mechanical effects of HPP on mixture systems are discussed. The mechanism of dairy protein gelation under pressure, their properties and microstructure, and potential application of HPP to improve physical properties of dairy products (cheese, yoghurt, and ice cream) are included. HPP is a promising tool for future manufacturing of structured dairy products with unique sensorial properties.     

Characterization of aerobic spore-forming bacteria associated with industrial dairy processing environments and product spoilage

Due to changes in the design of industrial food processing and increasing international trade, highly thermoresistant spore-forming bacteria are an emerging problem in food production. Minimally processed foods and products with extended shelf life, such as milk products, are at special risk for contamination and subsequent product damages, but information about origin and food quality related properties of highly heat-resistant spore-formers is still limited. Therefore, the aim of this study was to determine the biodiversity, heat resistance, and food quality and safety affecting characteristics of aerobic spore-formers in the dairy sector. Thus, a comprehensive panel of strains (n = 467), which originated from dairy processing environments, raw materials and processed foods, was compiled. The set included isolates associated with recent food spoilage cases and product damages as well as isolates not linked to product spoilage. Identification of the isolates by means of Fourier-transform infrared spectroscopy and molecular methods revealed a large biodiversity of spore-formers, especially among the spoilage associated isolates. These could be assigned to 43 species, representing 11 genera, with Bacillus cereus s.l. and Bacillus licheniformis being predominant. A screening for isolates forming thermoresistant spores (TRS, surviving 100 °C, 20 min) showed that about one third of the tested spore-formers was heat-resistant, with Bacillus subtilis and Geobacillus stearothermophilus being the prevalent species. Strains producing highly thermoresistant spores (HTRS, surviving 125 °C, 30 min) were found among mesophilic as well as among thermophilic species. B. subtilis and Bacillus amyloliquefaciens were dominating the group of mesophilic HTRS, while Bacillus smithii and Geobacillus pallidus were dominating the group of thermophilic HTRS. Analysis of spoilage-related enzymes of the TRS isolates showed that mesophilic strains, belonging to the B. subtilis and B. cereus groups, were strongly proteolytic, whereas thermophilic strains displayed generally a low enzymatic activity and thus spoilage potential. Cytotoxicity was only detected in B. cereus, suggesting that the risk of food poisoning by aerobic, thermoresistant spore-formers outside of the B. cereus group is rather low.     

Current performance of food safety management systems of dairy processing companies in Tanzania

A food safety management system (FSMS)‐diagnostic instrument was applied in 22 dairy processing companies to analyse the set‐up and operation of core control and assurance activities in view of the risk characteristics of the systems' context. Three clusters of companies were identified differing in levels of set‐up and operation of this FSMS and system outputs, but all operated in a similar moderate‐risk context. Microbiological assessment of products, environmental and hand samples indicated a poor to moderate food safety level. A two stage intervention approach has been proposed to enable commitment and sustainable improvement for the longer term.     

Occurrence of aerobic bacterial endospores in dried dairy ingredients

The present study investigated types of bacterial endospores in powdered dairy ingredients. For enumeration, the samples were heat-treated at 80°C/12 min for regular spore type, 100°C/30 min for high-heat-resistant spores (HHRS), and 106°C/30 min for specially thermoresistant spores (STS), followed by incubation for 24 h at 37°C (for mesophiles) and 55°C (for thermophiles). Of the three types, the regular spore type (80°C/12 min) was observed to be the most prominent endospore type, and Bacillus licheniformis as the predominant bacterial species in the tested dairy ingredients. This study would be helpful to utilise dry ingredients based on the potential activation of endospores during the product manufacturing processes.     

超声波在乳品行业中的作用

综述了乳品工业中超声灭菌、超声乳化和均质、超声清洗等方面的进展，同时也介绍了超声波在微生物代谢方面的应用，并分析了目前乳品行业中超声波技术的实际应用问题和解决方法。     

An overview of various technologies for the treatment of dairy wastewaters

Dairy industries have shown tremendous growth in size and number in most countries of the world. These industries discharge wastewater which is characterized by high chemical oxygen demand, biological oxygen demand, nutrients, and organic and inorganic contents. Such wastewaters, if discharged without proper treatment, severely pollute receiving water bodies. In this article, the various recent advancements in the treatment of dairy wastewater have been discussed and the areas where further research is needed have been identified.     

In-line viscometry in the dairy processing industry

The viscosity of a fluid, or fluid like material, is a measure of its resistance to flow. Many foods are fluid in nature, as final products and/or during production. The viscosity of the final product is an indicator of product consistency and can determine consumer preferences. During production a suitable and reliable in-line viscometer can help monitor the process, optimize yield, increase efficiency, reduce costs, enable a degree of automated control and improve final product consistency and quality. Whether such goals can be achieved in practice depends on many factors. This paper gives an overview of these factors.     

牛奶加工系统的卫生保证

<正> 在牛奶的加工过程中,产品会遭受到多方面的污染,包括设备表面、人、空气和水。其中设备表面是最主要的污染源,这包括直接的设备—产品接触对产品本身带来的污染,以及间接的生产环境对产品带来的污染,如地面、排水及清洗等工序。因此,系统的卫生保证,关键在于设备污染源的控制。     

乳扇加工工艺的优化

研究了乳扇的加工工艺.通过单因素实验、响应面优化得到制作乳扇的最佳工艺条件为熟烫温度75℃,酶反应pH值为6.0、凝乳温度34℃.采用优化工艺制作的产品口感、质地及理化指标均优于民间乳扇,为乳扇的产业化提供了基础数据.     

Thermophilic bacilli and their importance in dairy processing

The thermophilic bacilli, such as Anoxybacillus flavithermus and Geobacillus spp., are an important group of contaminants in the dairy industry. Although these bacilli are generally not pathogenic, their presence in dairy products is an indicator of poor hygiene and high numbers are unacceptable to customers. In addition, their growth may result in milk product defects caused by the production of acids or enzymes, potentially leading to off-flavours. Dairy thermophiles are usually selected for by the conditions during dairy manufacture. These bacteria are able to grow in sections of dairy manufacturing plants where temperatures reach 40-65 °C. Furthermore, because they are spore formers, they are difficult to eliminate. In addition, they exhibit a wide temperature growth range, exhibit a fast growth rate (generation time of approximately 15-20 min) and tend to readily form biofilms. Many strategies have been tested to remove, prevent and/or delay the formation of thermophilic bacilli biofilms in dairy manufacture, but with limited success. This is, in part, because little is known about the structure and composition of thermophilic bacilli biofilms in general and, more specifically, in milk processing environments. Therefore, new cleaning regimes often do not target the problem optimally. A greater understanding of the structure of thermophilic biofilms within the context of the milk processing environment and their link with spore formation is needed to develop better control measures. This review discusses the characteristics and food spoilage potential, enumeration and identification methods for the thermophilic bacilli, as well as their importance to dairy manufacture, with an emphasis on biofilm development and spore formation.     

乳品加工中高新技术的应用

介绍了新兴的现代生物技术、膜分离技术、超高压杀菌技术等高新加工技术在传统乳品加工中的应用，展现了良好的处理效果和应用前景。     

乳品加工中的清洗消毒与保鲜技术

主要介绍了乳品加工企业每班必遇的原料乳保鲜、产前消毒、班后清洗与工作环境的杀菌消毒等技术措施。同时,还详细介绍了两种新型高效环保型的消毒剂在乳品加工业中的应用。      

超声波技术在乳品加工中的应用

牛乳及乳制品容易变质,并且易出现分层等不良现象.所以应该对其进行有效的杀菌和均质,从而延长其保质期,提高产品品质.超声波是一种有效的非热力杀菌方法,具有均质和细胞破壁等作用,而且超声波灭菌不仅不会改变食品的色、香、味,而且不会破坏食品的组成成分.本文就超声波在乳品加工中的应用展开论述.     

The effect of treating whole-plant barley with Lactobacillus buchneri 40788 on silage fermentation,aerobic stability,and nutritive value for dairy cows

Chopped barley forage was ensiled untreated or treated with several doses (1 x 10(5) to 1 x 10(6) cfu/g of fresh forage) of Lactobacillus buchneri 40788 in laboratory silos and untreated or treated (4 x 10(5) cfu/g) in a farm silo. Silage from the farm silos was fed to lactating cows. In the laboratory silo, the effects of inoculation on fermentation and aerobic stability were also compared to silage treated with a commercial inoculant and a buffered propionic acid additive. Inoculation with L. buchneri 40788 decreased the final concentrations of lactic acid but increased concentrations of acetic acid and ethanol in silage from laboratory and farm silos. Silages stored in laboratory silos did not heat after exposure to air for 7 d and were then mixed with alfalfa silage and a concentrate to form total mixed rations (TMR) that were further exposed to air. The TMR containing silages treated with L. buchneri 40788 or a buffered propionic-acid-based additive took longer to heat and spoil than the TMR containing untreated silage or silagetreated with the commercial inoculant. Silage stored in a farm silo and treated with L. buchneri 40788 had fewer yeasts and molds than did untreated silage. Aerobic stability was greater in treated silage alone and in a TMR containing treated silage. Dry matter intake (18.6 kg/d), milk production (25.7 kg/d), and milk composition did not differ between cows fed a TMR containinguntreated or treated silage. These findings show that L. buchneri can improve the aerobic stability of barley silage in laboratory and farm silos and that feeding treated silage had no negative effect on intake or performance.     

Water use efficiency of Irish dairy processing

Dairy processing uses a significant amount of water for processing and cleaning. Withdrawing and distributing water and treating wastewater represent significant costs to the Irish dairy processing industry. Stringent discharge limits also add pressure for water use efficiency, particularly during peak production months. Improving water use efficiency is therefore critical for Irish dairy processing. We conducted a detailed analysis of water use efficiency in 4 Irish dairy processing plants. Using farm gate to processor gate (gate-to-gate) life cycle assessment, we assessed on-site water data quality and investigated gate-to-gate volumetric water use and eutrophication potential (EP) for 3 common dairy products. We also benchmarked the on-site water use and water balance, characterized wastewater nutrient load, analyzed the influencers of on-site water use, and identified scope for increased water use efficiency. We found that condensate from evaporation represented a significant input at the site level (0.51 to 1.14 L/L of fresh water purchased or extracted from nature). In terms of gate-to-gate volumetric water use, butter used 1,326 to 1,843 m³/t of solids, with electricity being the largest contributor, whereas milk powders used 3,006 to 3,754 m³/t of solids, with electricity and ingredients being the largest contributors. Eutrophication of butter was found to be 0.51 to 0.77 kg of PO₄ equivalents (eq)/t of solids, with transportation and nutrient emissions from wastewater treatment being the largest contributors. Eutrophication of milk powder was found to be 0.96 to 3.35 kg of PO₄ eq/t of solids, and contributions varied depending on powder specifications. Milk intake water use and various leakages were found to be hotspots that could be managed to reduce water use on site. Comprehensive metering is urgently needed to improve water use efficiency in light of the ongoing expansion of dairy production and hence processing in Ireland. Significant opportunities exist to optimize operator behavior, water reuse, and off-site transportation and energy. This study represents the first attempt to define water efficiency opportunities both at the site level and along the supply chain. Processors need to be aware of off-site contributors that significantly affect both volumetric water use and environmental impacts of processed dairy products.     

The effect of treating alfalfa with Lactobacillus buchneri 40788 on silage fermentation,aerobic stability,and nutritive value for lactating dairy cows

Lactobacillus buchneri 40788 and enzymes (beta-glucanase, alpha-amylase, xylanase, and galactomannase) were applied to chopped alfalfa (39% DM) to study their effects on the fermentation and nutritive value of the silage. Alfalfa was treated with nothing, or L. buchneri 40788, for a final application rate of 1 x 10(5), 5 x 10(5), or 1 x 10(6) cfu/g of fresh forage and ensiled in laboratory silos for 2, 4, 8, and 56 d. Treatment with L. buchneri 40788 had few effects on the end products of fermentation through 8 d of ensiling. However, after 56 d of ensiling, treated silages had a higher pH (4.55 vs. 4.38) and higher concentrations of acetic acid (6.40 vs. 4.24%), propionic acid (0.18 vs. 0.06%), and ammonia-N (0.35 vs. 0.29%) when compared to untreated silage. Lactic acid was also numerically lower in treated (3.51%) than untreated (4.12%). Silages treated with the moderate and highest dose of L. buchneri 40788 also resulted in greater recoveries of DM than did untreated silage. Alfalfa (43% DM) was also untreated or treated with a commercial application of L. buchneri 40788 (4 x 10(5) cfu/g, a commercial dose) in farm-scale bag silo. Holstein cows were fed a diet comprised of 32% untreated or treated alfalfa silage, 11% corn silage, 5% chopped alfalfa hay, and 52% of concentrate (DMB) for a 6-wk treatment period. Dry matter intake and milk composition were unaffected by treatment, but cows fed silage treated with L. buchneri 40788 produced 0.8 kg more milk than did cows fed untreated silage. Treated silage had a higher concentration of acetic acid (5.67 vs. 3.35%) but lower lactic acid (3.50 vs. 4.39%) than untreated silage. When exposed to air, the total mixed ration containing treated alfalfa silage remained stable for 100 h, whereas the ration containing untreated silage spoiled after 68 h. Treating alfalfa silage with L. buchneri 40788 increased the concentration of acetic acid, and when the silage was combined into a total mixed ration and fed to lactating cows, it improved the aerobic stability of the ration and increased milk production.     

Adsorption at interfaces in dairy systems*

Factors affecting the composition of fluid interfaces in dairy systems are assessed from a physicochemical viewpoint. Attention is directed towards recent developments in understanding time-dependent and competitive aspects of the adsorption of milk proteins and small-molecule surfactants at oil-water and air-water interfaces. Experimental results are described for various casein and whey protein systems. The relationship between adsorption behaviour and the ease of formation and stabilization of dairy emulsions and foams is discussed with reference to model systems and commercial dairy products.     

Cold plasma processing of milk and dairy products

BackgroundThermal pasteurization and sterilization are predominantly used in the dairy industry due to their efficacy in improving the product safety and shelf life. However, heat treatment can cause undesirable protein denaturation, non-enzymatic browning, loss of vitamins and volatile flavor compounds, freezing point depression, and flavour changes. Cold plasma is a non-thermal technology that has gained attention in recent years as a potential alternative method for chemical and thermal disinfection in foods using ambient or moderate temperatures and short treatment times.Scope and approachThis review aims to describe the fundamentals, parameters, and technology on cold plasma, discussing the critical processing factors involved in this technology. Also, it describes the mechanisms of microbial inactivation and provides an overview of the effects of non-thermal plasma on the quality of dairy products, considering a physicochemical, sensory and microbiology perspective.Key findings and conclusionsCold plasma uses less aggressive mechanisms of action to the milk matrix when compared to the techniques currently used, and has shown an excellent performance on the elimination of pathogenic and spoilage microorganisms besides maintaining, in many cases, the nutritional, functional, and sensory characteristics of the product.