Shelf life of whole pasteurized milk in Greece: effect of packaging material

Evaluation of in vitro bioassays as a screening tool to monitor chemical hazards in cow's milk

Studies on cow's milk have mainly focused on analyzing specific chemical groups and natural components. Therefore, in this study, we evaluated if effect-based in vitro methods could be used as a screening tool to monitor chemical hazards in milk. In total, 32 milk samples were collected from a Swedish dairy company throughout one year. These samples included conventional and organic semi-skimmed as well as raw milk. The milk samples were tested in five in vitro methods covering eight endpoints. These endpoints included cytotoxicity, endocrine disruption (estrogen/androgen induction/inhibition), aryl hydrocarbon receptor activity, oxidative stress and DNA damage. Estrogen and androgen receptor inhibition, in addition to aryl hydrocarbon receptor activity, were the most responsive endpoints, where 10 to 13 out of the 32 milk samples were bioactive. Organic and conventional milk showed no major differences. Overall, no or only low activities were observed in milk samples in the remaining in vitro assays, which is a promising result with regard to applying effect-based methods as a screening tool. Concerning the most responsive assays, more research is needed to understand the normal background variations before they can be used as a screening tool for chemical hazards in milk.

Life cycle assessment (LCA) of bio-based packaging solutions for extended shelf-life (ESL) milk

The dairy market is one of the most important sectors worldwide, and milk packaging contributes to over one-third of the global dairy packaging demand. The end of life of the disposable packages is a critical stage of their life cycle, as demonstrated by the fact that disposable bottles are one of the litter items that are most found on beach shores. The aim of this paper is to analyse the performance of bioplastic bottles compared to other alternatives currently in use in the milk packaging sector, using the life cycle assessment (LCA) methodology. Bio-compostable plastic can be a powerful means to create a circular economy for disposable items. A PLA-based bottle is compared to a PET bottle, a HDPE bottle, a multilayer carton, and a glass bottle. In the analysis, also secondary and tertiary packaging is included. The functional unit chosen is "the packaging needed to contain 1 L of ESL milk and to guarantee a shelf life of 30 days". Two sensitivity analyses are also performed in order to assess the influence of the end-of-life stage on the total impact. The results show that, in accordance with the assumptions of an ideal scenario, bioplastic system has a better performance than fossil-based systems and multilayer carton in the categories of climate change, ozone depletion, human toxicity, freshwater eutrophication, particular matter, and land use. The recycling scenario strongly changes the impact of the glass packaging system in the considered categories.

Invited review: Maintaining and growing fluid milk consumption by children in school lunch programs in the United States

Fluid milk consumption among children has declined for decades. Adequate consumption of milk and dairy products, especially during childhood, has beneficial health outcomes for growth, development, and reduced risk of osteoporosis, hypertension, obesity, and cancer during adulthood. Satisfaction with milk flavor, perceived health benefits derived from milk, and habit are primary drivers of lifelong milk consumption. Child preferences and attitudes for milk may differ from those of adults, and as such, understanding and fulfilling the needs of children is crucial to reverse the decline in milk consumption. School meal programs make fluid milk accessible to millions of children each day; however, regulations and school lunch procurement systems in the United States sometimes make it difficult to provide novel or value-added milk products in these programs. Total consumption of all milk types in US schools declined by 14.2% from 2008 to 2017, and the percentage of children participating in the school lunch program has also declined. This decline has also been driven by declining average daily participation in the school meal program and may also reflect children's dissatisfaction with the sensory characteristics and the form of milk offered in schools. The change in form of milk offered in schools to lower fat and lower added sugar content in the United States has been driven by government-mandated school lunch calorie and fat requirements. This review describes the current milk consumption trends among children; the structure and basic requirements of the school lunch program in total and for milk; and the intrinsic, extrinsic, and environmental factors that influence child perception, preference, and consumption of fluid milk in the US school system.

Effect of HTST Thermal Treatments on End-Use Quality Characteristics of Goat Milk

Goat milk samples were pasteurized at high-temperature (72°C, 75°C, and 81°C) and in short-time (15 s and 25 s) combinations. Physical, chemical and microbial qualities of the pasteurized milk samples were evaluated 0, 2, 3, and 4 weeks of storage at 4°C. Despite the different thermal treatments, specific-gravity and viscosity were comparatively stable immediately after pasteurization (IAP). The viscosity of pasteurized milk at 81°C showed significant increase (P < 0.05) from 1.58 ± 0.18 to 2.30 ± 0.15 mPa s during four weeks of storage. Relative lightness “L” value decreased by about 10% during the storage period of 81°C pasteurization samples. Acidity increased with heat treatment irrespective of holding time, but in 81°C pasteurized sample higher acidity was developed at end of the storage. Fat oxidation 2-3 times higher at 81°C than 72°C pasteurized samples. Total protein (TP%) and nonprotein nitrogen contents were stable IAP but TP reduced significantly (P < 0.05) at two weeks storage. The whey protein denaturation increased with pasteurization treatments and storage time. Antioxidant activity of raw goat milk was 34.8 ± 5.01 μmol l⁻¹ and was decreased by 20–43% IAP compared to raw milk samples, but gradually increased during storage. IAP, mesophilic counts were in the range of 980–110 cfu ml⁻¹ (72°C/15–81°C/25 s) and increased from 2236 to 680 cfu ml⁻¹ samples stored at 4 weeks. Results showed that best quality stability of pasteurized goat milk achieved by heat treatments between 72°C/25 s and 75°C/25 s heat treatments up to 3 weeks of storage under 4°C.

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.

Bactéries sporulées et biofilms : un problème récurrent dans les lignes de production de lait reconstitué ou recombiné pasteurisé

In the dairy industry, bacterial contaminants persist on equipment surfaces due to spore and biofilm formation. These are involved in cross-contamination problems that affect the quality of processed products and limit their life. The pasteurization process, in which milk is submitted to moderate heat treatment, is inefficient against bacterial spores. The most prevalent sporulated bacteria belong to Bacillus and related genera. The situation is more complicated in countries where pasteurized milk is derived from imported milk powder originally contaminated by bacterial spores. Studies have shown biofilm formation on dairy equipment by mesophilic strains from the group Bacillus cereus and thermophilic strains from the genus Geobacillus. These biofilms are resistant to cleaning procedures and are sources of chronic contamination of pasteurized milk. This review analyzes the dairy situation in Algeria exposed to sporulated flora and derived biofilm problems, with the aim of proposing efficient solutions in the light of current knowledge. [Journal translation].

Antioxidant properties of Milk and dairy products: a comprehensive review of the current knowledge

Milk and dairy products are integral part of human nutrition and they are considered as the carriers of higher biological value proteins, calcium, essential fatty acids, amino acids, fat, water soluble vitamins and several bioactive compounds that are highly significant for several biochemical and physiological functions. In recent years, foods containing natural antioxidants are becoming popular all over the world as antioxidants can neutralize and scavenge the free radicals and their harmful effects, which are continuously produced in the biological body. Uncontrolled free radicals activity can lead to oxidative stresses, which have been implicated in breakdown of vital biochemical compounds such as lipids, protein, DNA which may lead to diabetes, accelerated ageing, carcinogenesis and cardiovascular diseases. Antioxidant capacity of milk and milk products is mainly due to sulfur containing amino acids, such as cysteine, phosphate, vitamins A, E, carotenoids, zinc, selenium, enzyme systems, superoxide dismutase, catalase, glutathione peroxidase, milk oligosaccharides and peptides that are produced during fermentation and cheese ripening. Antioxidant activity of milk and dairy products can be enhanced by phytochemicals supplementation while fermented dairy products have been reported contained higher antioxidant capacity as compared to the non-fermented dairy products. Literature review has shown that milk and dairy products have antioxidant capacity, however, information regarding the antioxidant capacity of milk and dairy products has not been previously compiled. This review briefly describes the nutritional and antioxidant capacity of milk and dairy products.

Vitamin Fortification of Fluid Milk

Vitamin concentrates with vitamins A and D are used for fortification of fluid milk. Although many of the degradation components of vitamins A and D have an important role in flavor/fragrance applications, they may also be source(s) of off-flavor(s) in vitamin fortified milk due to their heat, oxygen, and the light sensitivity. It is very important for the dairy industry to understand how vitamin concentrates can impact flavor and flavor stability of fluid milk. Currently, little research on vitamin degradation products can be found with respect to flavor contributions. In this review, the history, regulations, processing, and storage stability of vitamins in fluid milk are addressed along with some hypotheses for the role of vitamin A and D fortification on flavor and stability of fluid milk.

The microbiological quality of pasteurized milk sold by automatic vending machines

The microbiological quality of pasteurized milk samples (n = 39) collected during 13 weekly intervals from three automatic vending machines (AVM) in Greece was investigated. Microbiological counts (total aerobic (TAC), total psychrotrophic (TPC), Enterobacteriaceae (EC), and psychrotrophic aerobic bacterial spore counts (PABSC)) were obtained at the time of sampling and at the end of shelf-life (3 days) after storage of the samples at 4 or 8°C. TAC were found to be below the 10(7 ) CFU ml(-1) limit of pasteurized milk spoilage both during sampling as well as when milk samples were stored at either storage temperature for 3 days. Enterobacteriaceae populations were below 1 CFU ml(-1) in 69·2% of the samples tested at the time of sampling, whereas the remaining samples contained low numbers, typically less than 10 CFU ml(-1) . All samples tested negative for the presence of Listeria monocytogenes. Analogous microbiological data were also obtained by sampling and testing prepackaged, retail samples of pasteurized milk from two dairy companies in Greece (n = 26). From a microbiological standpoint, the data indicate that the AVM milk samples meet the quality standards of pasteurized milk. However, the prepackaged, retail milk samples yielded better results in terms of TAC, TPC and EC, compared to the AVM samples at the end of shelf-life.

SIGNIFICANCE AND IMPACT OF THE STUDY

Recently, Greek dairy farmers organized in cooperatives launched the sale of pasteurized milk via AVM and this study reports on the microbiological quality of this product. The data show that AVM milk is sold at proper refrigeration temperatures and meets the quality standards of pasteurized milk throughout the manufacturer's specified shelf-life. However, based on the microbiological indicators tested, the keeping quality of the tested prepackaged, retail samples of pasteurized milk at the end of shelf-life upon storage under suboptimal refrigeration temperature (8°C) was better.

Quality of sour cream packaged in cups with different light barrier properties measured by fluorescence spectroscopy and sensory analysis

In this study, photooxidation of sour cream packaged in cups with different light barrier properties was investigated. The sour cream was light exposed for 36 h with a standard fluorescent light tube, simulating storage conditions in many Norwegian grocery stores. Three different cups were evaluated: a white cup, a cup with medium light barrier (LB), and a cup with high LB. The quality of the sour cream was evaluated by sensory analysis and front face fluorescence spectroscopy. The sour cream stored in white cups became very rancid during the light exposure, with a rancid flavor score of 7.8 on a scale from 1 to 9, where 9 is the highest intensity. Cups with high LB gave best protection against the light. The sensory assessors could not distinguish between sour cream stored in cups with high LB and sour cream stored in the dark. The rancid flavor intensity for the cups with medium LB was significantly different (P < 0.05) from both the white cup and the cup with high LB. The sensory flavor intensities indicated that with 36 h of light exposure, only a cup with high LB will protect the sour cream sufficiently. The fluorescence measurements corresponded well with the sensory analysis as the photosensitizers were somewhat degraded for sour cream stored in cups with medium LB and most degraded in the white cups. For the cups with high LB, the fluorescence peaks that originated from the photosensitizers were all intact.

PRACTICAL APPLICATION

Dairy products such as sour cream will develop off-odor and taste faults ("sunlight taste") in a few hours if exposed to sufficient fluorescent lightning in the grocery stores. A light barrier can be incorporated in the packaging material to protect the dairy products from the light. Our experiment showed that the incorporation of a black pigment into 1 of the 3 plastic layers in the cup for packaging of sour cream protected the sour cream from degradation when exposed to light.

Attenuated total internal reflection infrared microscopy of multilayer plastic packaging foils

Multilayer plastic foils are important packaging materials that are used to extend the shelf life of food products and drinks. Fourier transform infrared (FT-IR) spectroscopic imaging using attenuated total internal reflection (ATR) can be used for the identification and localization of different layers in multilayer foils. A new type of ATR crystal was used in combination with a linear array detector through which large sample areas (400 x 400 microm(2)) could be imaged with a pixel size of 1.6 microm. The method was tested on laminated plastic packing materials containing 5 to 12 layers. The results of the identification of the different materials using ATR-FT-IR were compared with differential scanning calorimetry (DSC) and the layer thickness of the individual layers measured by ATR-FT-IR was compared with polarized light microscopy (LM) and scanning electron microscopy (SEM). It has been demonstrated that individual layers with a thickness of about 3 microm could be identified in multilayer foils with a total thickness ranging from 100 to 150 microm. The results show a spatial resolution of about 4 microm (measured at wavenumbers ranging from 1000 to 1730 cm(-1)), which is about a factor of two better than can be obtained using transmission FT-IR imaging. An additional advantage of ATR is the ease of sample preparation. A good correspondence was found between visible and FT-IR images. The results of ATR-FT-IR imaging were in agreement with those obtained by LM, SEM, and DSC. ATR-FT-IR is superior to the combination of these techniques because it delivers both spatial and chemical information.