Major Advances in Fresh Milk and Milk Products: Fluid Milk Products and Frozen Desserts

Mapping the meltdown behavior of frozen dairy desserts

The meltdown test is an efficient tool widely and commonly used to characterize structural changes in frozen desserts resulting from different ingredients and processing conditions. The meltdown is commonly determined by a gravimetric test, and it is used to obtain the onset (Mon), rate (Mrate), and maximum (MMax) meltdown. However, these parameters are calculated ambiguously due to inconsistencies in the methodology. This work aims to model the meltdown curves (weight vs. time) of different commercial frozen dessert samples (36 commercial samples). Samples of commercial frozen desserts (40-60 g) was placed on a 304 stainless wire cloth (1.50 mm opening size and 52% open area) suspended ∼15 cm above an analytical balance, and the dripped portion of the melted sample was continuously recorded throughout the duration of the test. The meltdown test was conducted at room temperature. Each meltdown test generated between 3,000 to 4,000 data points and was modeled using 4 equations: the logistic model, the Gompertz model, the Richard model, and the Hill model. All the meltdown curves were sigmoidal in shape, regardless of the type of frozen dessert. The experimental meltdown curves were adequately represented by the logistic model, judging by several criteria (R2 = 0.999, RAdj2 = 0.999, Akaike information criterion = 6,582, and F-value = 1.88 × 106). Thus, the logistic model was shown to be an effective tool for predicting the meltdown curves of frozen desserts, and it can be used to unambiguously define Mon, Mrate, and MMax. Moreover, a dimensionless response (meltdown behavior, MBe) that combines Mon, Mrate, and MMax was developed and used for mapping the meltdown of different commercial frozen desserts.

NIR Spectroscopy Assessment of Quality Index of Fermented Milk (Laban) Drink Flavored with Date Syrup during Cold Storage

Fermented milk (laban) with added date syrup can be an excellent candidate for a nutritious drink. Modeling with quality index (Qi) can assist in assessing the quality of the drink’s physiochemical properties. The properties of the laban drink fortified with date syrup were measured and modeled with Qi during shelf life (7 days), and then analyzed with near-infrared spectra (NIR). The aim of this study was to develop a quality index model for the laban drink properties (objective and sensory assessments) and then to predict Qi with a non-destructive measurement of NIR (with partial least-square regression (PLSR) and artificial neural network (ANN) analysis). The results revealed that the developed Qi fits well with measured laban drink properties (viscosity, color, total soluble solids, pH, and sensory assessments during the shelf-life period with R2 = 0.977). The NIR spectrum was efficient to estimate the quality index of the fortified laban drink. It was found that ANN is more appropriate than the PLSR model in estimating the Qi of the Laban drink during cold storage. Thus, non-destructive NIR can predict Qi and can be utilized with great success in the whole chain of production, processing, transportation, storage, and retail market to check the “quality” and “shelf life” of the product.

Physicochemical, Microbiological, and Sensorial Quality Attributes of a Fermented Milk Drink (Laban) Fortified with Date Syrup (Dibs) during Cold Storage

This study investigated the nutritional, microbial, and sensory quality attributes of a fermented milk (laban) drink flavored with date syrup (dibs) during cold storage at 4 °C for 7 days. Date syrup was added to laban in specific proportions (2.5, 5, 7.5, 10, 12.5, and 15% date syrup/total weight of flavored laban) and an appropriate percentage (12.5%, 74 °Bx) was selected based on the sensory preference of panelists. The results indicate that flavoring laban with date syrup affected the physicochemical, nutritional, microbial, and sensory quality attributes of the product in different ways. Incorporation of date syrup in fresh laban drink significantly increased the pH, ash, protein, total solids, sugars, and magnesium (p < 0.05). However, acidity, fat, casein, lactose, calcium, total microbial count, and total yeast and molds count were decreased (p < 0.05). During storage, acidity, ash, and microbial load were concomitantly increased, while fat, casein, total solids, and sugars showed a concurrent reduction as the storage period progressed. The panelists preferred the freshly prepared flavored laban drink compared with the stored one, which is not surprising. After 7 days of storage, flavored laban drink was more acceptable than a non-flavored one. The findings of this research will help in fortifying dairy products with dates to create highly nutritious drinks without the addition of artificial additives, refined sweeteners, and preservatives, which at the same time would be accepted by consumers.

Invited review: Controlling dairy product spoilage to reduce food loss and waste

Food loss and waste is a major concern in the United States and globally, with dairy foods representing one of the top categories of food lost and wasted. Estimates indicate that in the United States, approximately a quarter of dairy products are lost at the production level or wasted at the retail or consumer level annually. Premature microbial spoilage of dairy products, including fluid milk, cheese, and cultured products, is a primary contributor to dairy food waste. Microbial contamination may occur at various points throughout the production and processing continuum and includes organisms such as gram-negative bacteria (e.g., Pseudomonas), gram-positive bacteria (e.g., Paenibacillus), and a wide range of fungal organisms. These organisms grow at refrigerated storage temperatures, often rapidly, and create various degradative enzymes that result in off-odors, flavors, and body defects (e.g., coagulation), rendering them inedible. Reducing premature dairy food spoilage will in turn reduce waste throughout the dairy continuum. Strategies to reduce premature spoilage include reducing raw material contamination on-farm, physically removing microbial contaminants, employing biocontrol agents to reduce outgrowth of microbial contaminants, tracking and eliminating microbial contaminants using advanced molecular microbiological techniques, and others. This review will address the primary microbial causes of premature dairy product spoilage and methods of controlling this spoilage to reduce loss and waste in dairy products.

Effect of nisin and lysozyme on bacteriological and sensorial quality of pasteurized milk

Objectives:

The objective of this study was to evaluate the impact of the antimicrobials nisin and lysozyme to control the growth of spoilage bacteria of pasteurized milk during cold storage.

Materials and Methods:

Nisin, lysozyme, and a mixture of them were inoculated into freshly pasteurized milk at 500 IU/ml concentrations each. The acidity, sensory evaluation, and bacteriological quality of the treated pasteurized milk samples were examined at zero time and every 3 days till the samples showed the signs of spoilage, that were checked every day.

Results:

Obtained results showed that there was a slight increase of the titratable acidity of the control and treated samples during refrigerated storage, but the acidity increase was significantly lower in samples containing lysosomes and/or nisin than the control samples. Nisin and lysozyme at 500 IU/ml concentration possessed inhibitory effect on the total bacterial, aerobic spore-formers, and psychrotrophic bacterial counts and extended the shelf-life of the treated samples. The efficacy of nisin 500 IU/ml combined with lysozyme 500 U/ml was assessed and synergistic activity has been detected, that was expressed in the form of higher inhibitory effect and extending the shelf-life of the samples up to 15 days at cold storage. Moreover, the sensory evaluation showed that nisin and lysozyme does not affect the acceptability of the examined samples.

Conclusion:

The obtained data indicate that nisin and lysozyme have the potential to enhance the post-process bacteriological safety of pasteurized milk during the storage period and could aid in the elimination of post-process contamination and prolong its shelf-life.

Physicochemical and sensory properties of milk supplemented with lactase microcapsules coated with enteric coating materials

In this paper, we report the physicochemical and sensory properties of milk supplemented with a powder of microencapsulated lactase. The core material was lactase (β-galactosidase), the primary coating material was medium-chain triglyceride (MCT), and the secondary (enteric) coating material was either hydroxypropyl methylcellulose phthalate (HPMCP) or shellac, comparing both against market milk as a control. The physicochemical properties of both types of microcapsules were analyzed, including the particle size, zeta potential, and in vitro release behavior. To survey the stability of the microcapsules in milk during storage, we studied the residual lactose content and pH. Furthermore, to determine the properties of milk supplemented with the microcapsules, changes in color and sensory properties were evaluated during storage. The particle sizes (volume-weighted mean; D[4,3]) of the microcapsules coated with HPMCP or shellac were 2,836 and 7,834 nm, respectively, and the zeta potential of the capsules coated with shellac was higher than the zeta potential of those coated with HPMCP. The pH levels of milk supplemented with the lactase microcapsules were similar to those of the control (unsupplemented market milk); however, for milk supplemented with HPMCP-coated microcapsules, the pH was slightly lower. The core material, lactase, was released from the microcapsules during 12-d storage, and 18.82 and 35.09% of lactose was hydrolyzed in the samples for HPMCP- and shellac-coated microcapsules, respectively. The sensory characteristics of milk containing microcapsules coated with HPMCP did not show significant differences from the control, in terms of sweetness or off-taste, until 8 d of storage. However, shellac-coated microcapsules showed significant difference in sweetness and off-taste at d 8 and 6 of storage, respectively. The color of milk containing HPMCP-coated microcapsules did not show a significant difference during storage. However, that containing shellac-coated microcapsules was somewhat higher in color values than others. In particular, it showed significance from 0 to 4 d storage in L* and C* values. In conclusion, a powder of lactase microcapsules coated with HPMCP can be suitable as a supplement for milk.

Novel trends in engineered milk products

Food engineering within the dairy sector is an ever developing field of study purely based on the application of engineering principles and concepts to any aspect of dairy product manufacturing and operations. The last 25 years of science and technology devoted to milk and milk products have led to major advances. The purpose of this paper is to review the history and current status of some engineered milk products and to speculate regarding future trends. Much of the advancement has been directed towards production capacity, mechanisation, automation, hygiene within the processing plant, safety, extensions in shelf life, and new product introductions that bring variety and convenience for the consumer. Significant advancements in product quality have been made, many of these arising from improved knowledge of the functional properties of ingredients and their impact on structure and texture. In addition, further improvements focused on energy efficiency and environmental sustainability have been made and will be needed in the future.

Evaluation of different methods to detect microbial hygiene indicators relevant in the dairy industry

It is estimated that 19% of the total food loss from retail, food service, and households comes from dairy products. A portion of this loss may be attributed to premature spoilage of products due to lapses in sanitation and postpasteurization contamination at the processing level. Bacterial groups including coliforms, Enterobacteriaceae (EB), and total gram-negative organisms represent indicators of poor sanitation or postpasteurization contamination in dairy products worldwide. Although Petrifilms (3M, St. Paul, MN) and traditional selective media are commonly used for the testing of these indicator organism groups throughout the US dairy industry, new rapid methods are also being developed. This project was designed to evaluate the ability of different methods to detect coliforms, EB, and other gram-negative organisms isolated from various dairy products and dairy processing environments. Using the Food Microbe Tracker database, a collection of 211 coliform, EB, and gram-negative bacterial isolates representing 25 genera associated with dairy products was assembled for this study. We tested the selected isolates in pure culture (at levels of approximately 15 to 300 cells/test) to evaluate the ability of 3M Coliform Petrifilm to detect coliforms, 3M Enterobacteriaceae Petrifilm, violet red bile glucose agar, and an alternative flow cytometry-based method (bioMérieux D-Count, Marcy-l'Étoile, France) to detect EB, and crystal violet tetrazolium agar to detect total gram-negative organisms. Of the 211 gram-negative isolates tested, 82% (174/211) had characteristic growth on crystal violet tetrazolium agar. Within this set of 211 gram-negative organisms, 175 isolates representing 19 EB genera were screened for detection using EB selective/differential testing methods. We observed positive results for 96% (168/175), 90% (158/175), and 86% (151/175) of EB isolates when tested on EB Petrifilm, violet red bile glucose agar, and D-Count, respectively; optimization of the cut-off thresholds for the D-Count may further improve its sensitivity and specificity, but will require additional data and may vary in food matrices. Additionally, 74% (129/175) of the EB isolates tested positive as coliforms. The data obtained from this study identify differences in detection between 5 microbial hygiene indicator tests and highlight the benefits of EB and total gram-negative testing methods.

Perspective of membrane technology in dairy industry: a review

Membrane technology has revolutionized the dairy sector. Different types of membranes are used in the industry for various purposes like extending the shelf life of milk without exposure to heat treatment, standardization of the major components of milk for tailoring new products as well increasing yield and quality of the dairy products, and concentrating, fractionation and purification of milk components especially valuable milk proteins in their natural state. In the cheese industry, membranes increase the yield and quality of cheese and control the whey volume, by concentrating the cheese milk. With the advancement of newer technology in membrane processes, it is possible to recover growth factor from whey. With the introduction of superior quality membranes as well as newer technology, the major limitation of membranes, fouling or blockage has been overcome to a greater extent.

Computer simulation of energy use, greenhouse gas emissions, and costs for alternative methods of processing fluid milk

Computer simulation is a useful tool for benchmarking electrical and fuel energy consumption and water use in a fluid milk plant. In this study, a computer simulation model of the fluid milk process based on high temperature, short time (HTST) pasteurization was extended to include models for processes for shelf-stable milk and extended shelf-life milk that may help prevent the loss or waste of milk that leads to increases in the greenhouse gas (GHG) emissions for fluid milk. The models were for UHT processing, crossflow microfiltration (MF) without HTST pasteurization, crossflow MF followed by HTST pasteurization (MF/HTST), crossflow MF/HTST with partial homogenization, and pulsed electric field (PEF) processing, and were incorporated into the existing model for the fluid milk process. Simulation trials were conducted assuming a production rate for the plants of 113.6 million liters of milk per year to produce only whole milk (3.25%) and 40% cream. Results showed that GHG emissions in the form of process-related CO₂ emissions, defined as CO₂ equivalents (e)/kg of raw milk processed (RMP), and specific energy consumptions (SEC) for electricity and natural gas use for the HTST process alone were 37.6g of CO₂e/kg of RMP, 0.14 MJ/kg of RMP, and 0.13 MJ/kg of RMP, respectively. Emissions of CO2 and SEC for electricity and natural gas use were highest for the PEF process, with values of 99.1g of CO₂e/kg of RMP, 0.44 MJ/kg of RMP, and 0.10 MJ/kg of RMP, respectively, and lowest for the UHT process at 31.4 g of CO₂e/kg of RMP, 0.10 MJ/kg of RMP, and 0.17 MJ/kg of RMP. Estimated unit production costs associated with the various processes were lowest for the HTST process and MF/HTST with partial homogenization at $0.507/L and highest for the UHT process at $0.60/L. The increase in shelf life associated with the UHT and MF processes may eliminate some of the supply chain product and consumer losses and waste of milk and compensate for the small increases in GHG emissions or total SEC noted for these processes compared with HTST pasteurization alone. The water use calculated for the HTST and PEF processes were both 0.245 kg of water/kg of RMP. The highest water use was associated with the MF/HTST process, which required 0.333 kg of water/kg of RMP, with the additional water required for membrane cleaning. The simulation model is a benchmarking framework for current plant operations and a tool for evaluating the costs of process upgrades and new technologies that improve energy efficiency and water savings.

Uso de microfiltração para melhoria da qualidade e extensão da vida de prateleira de leite pasteurizado

A microfiltração é uma das tecnologias utilizadas para melhorar a qualidade do leite fluido. O objetivo dessa revisão é abordar o uso da microfiltração do leite para estender sua vida de prateleira. A importância da qualidade do leite cru (microorganismos contaminantes e enzimas naturais do leite, provenientes das células somáticas ou do crescimento dos microrganismos psicrotróficos) e as condições de estocagem do leite cru (refrigeração), que são decisivas para a qualidade e vida de prateleira do leite pasteurizado, também serão discutidas. São mencionados os progressos já obtidos e em desenvolvimento da tecnologia de microfiltração para a extensão da vida de prateleira do leite pasteurizado e a importância da microfiltração para manter as características nutricionais do leite. Ainda serão descritos os problemas associados com incrustações da membrana que afetam o seu desempenho.

A risk assessment model for enterotoxigenic Staphylococcus aureus in pasteurized milk: a potential route to source-level inference

This article describes a probabilistic model that quantifies hazards that arise from Staphylococcus aureus in milk that is sold as pasteurized in the United Kingdom. The model is centered on coupled dynamics for S. aureus populations, staphylococcal enterotoxins, and the concentration of alkaline phosphatase throughout the milk chain. The chain includes farm collection and storage of pooled milk, further pooling for off-farm processing, high temperature short time thermal processing, and possible postprocess contamination. The model is implemented as a Bayesian belief network. The results indicate that milk sold as pasteurized is relatively safe with respect to the hazards associated with S. aureus and that most risk is associated with small scale on-farm processing. An additional analysis of likelihood ratios shows that alkaline phosphatase concentrations in filler tank milk are a good indicator of potential hazards and that these concentrations, in conjunction with other measurements, can be used effectively to discriminate over possible failure modes. The ability to discriminate over potential failure modes can support preemptive actions, such as maintenance or hygiene, which assist with milk chain management and, over extended periods, accumulate to drive improved safety, efficiency, and security.

Food safety: unpasteurized milk: a continued public health threat

Although milk and dairy products are important components of a healthy diet, if consumed unpasteurized, they also can present a health hazard due to possible contamination with pathogenic bacteria. These bacteria can originate even from clinically healthy animals from which milk is derived or from environmental contamination occurring during collection and storage of milk. The decreased frequency of bovine carriage of certain zoonotic pathogens and improved milking hygiene have contributed considerably to decreased contamination of milk but have not, and cannot, fully eliminate the risk of milkborne disease. Pasteurization is the most effective method of enhancing the microbiological safety of milk. The consumption of milk that is not pasteurized increases the risk of contracting disease from a foodstuff that is otherwise very nutritious and healthy. Despite concerns to the contrary, pasteurization does not change the nutritional value of milk. Understanding the science behind this controversial and highly debated topic will provide public health care workers the information needed to discern fact from fiction and will provide a tool to enhance communication with clients in an effort to reduce the incidence of infections associated with the consumption of unpasteurized milk and dairy products.

Milk Fat Globule structure & function; nanosciece comes to milk production

The biological process of fat globule assembly and secretion produces highly complex globule compositions and structures with many properties now recognized to be the direct result of these structures. During homogenization, fat globules are broken down and subsequently structures and surfaces different than the native state are formed. This process alters the milk fat globule unique macrostructure and the effects associated to their structure would be expected to be lost. In the present overview, the need for continued research of the fundamental aspects of the mechanism involved in milk fat globules synthesis secretion and size distribution, as well as establishing ways to regulate those processes are highlighted. Ultimately these insights will guide food technology to developing a new generation of structure based functional foods and as highlighted in this overview, dairy functional products should be the pioneering commodity.

Detection of pH 4.6 insoluble beta-lactoglobulin in heat-treated milk and Mozzarella cheese

Different protein aggregates including beta-lactoglobulin (beta lg) were detected in the pH 4.6 insoluble fraction recovered from actual heat-treated milk samples by gel electrophoresis and immunoblotting. A competitive enzyme-linked immunosorbent assay (ELISA) using anti-beta lg polyclonal antibodies was developed to analyze the beta lg partition in the protein fractions obtained upon acidification of both milk and Mozzarella cheese at pH 4.6. According to ELISA determinations, nearly 90% of the pH 4.6 soluble beta lg included in raw milk was found in the pH 4.6 insoluble fraction of ultrahigh temperature (UHT)-treated milk. As concerns Mozzarella cheese analysis, ELISA results indicated that about 36% of the total beta lg milk content was transferred from pasteurized milk to Mozzarella cheese, whereas less than 0.5% was transferred from raw milk. The pH 4.6 insoluble beta lg proved to be a suitable indicator of the intensity of the heat treatment applied to milk. The ELISA-based detection of this parameter was suggested for quality control of both drinking milk and raw milk cheese.

Antimicrobial activity of clove and cinnamon essential oils against Listeria monocytogenes in pasteurized milk

The antimicrobial activity of essential oils (EOs) of cinnamon bark, cinnamon leaf, and clove against Listeria monocytogenes Scott A were studied in semiskimmed milk incubated at 7 degrees C for 14 days and at 35 degrees C for 24 h. The MIC was 500 ppm for cinnamon bark EO and 3,000 ppm for the cinnamon leaf and clove EOs. These effective concentrations increased to 1,000 ppm for cinnamon bark EO, 3,500 ppm for clove EO, and 4,000 ppm for cinnamon leaf EO when the semiskimmed milk was incubated at 35 degrees C for 24 h. Partial inhibitory concentrations and partial bactericidal concentrations were obtained for all the assayed EOs. The MBC was 3,000 ppm for the cinnamon bark EO, 10,500 ppm for clove EO, and 11,000 ppm for cinnamon leaf EO. The incubation temperature did not affect the MBC of the EOs but slightly increased the MIC at 35 degrees C. The increased activity at the lower temperature could be attributed to the increased membrane fluidity and to the membrane-perturbing action of EOs. The influence of the fat content of milk on the antimicrobial activity of EOs was tested in whole and skimmed milk. In milk samples with higher fat content, the antimicrobial activity of the EOs was reduced. These results indicate the possibility of using these three EOs in milk beverages as natural antimicrobials, especially because milk beverages flavored with cinnamon and clove are consumed worldwide and have been increasing in popularity in recent years.