Maillard Reaction Products as Encapsulants for Fish Oil Powders

The use of Maillard reaction products for encapsulation of fish oil was investigated. Fish oil was emulsified with heated aqueous mixtures comprising a protein source (Na caseinate, whey protein isolate, soy protein isolate, or skim milk powder) and carbohydrates (glucose, dried glucose syrup, oligosaccharide) and spray‐dried for the production of 50% oil powders. The extent of the Maillard reaction was monitored using L*, a*, b* values and absorbance at 465 nm. Encapsulation efficiency was gauged by measurement of solvent‐extractable fat and the oxidative stability of the fish oil powder, which was determined by assessment of headspace propanal after storage of powders at 35 °C for 4 wk. Increasing the heat treatment (60 °C to 100 °C for 30 to 90 min) of sodium caseinate‐glucose‐glucose syrup mixtures increased Maillard browning but did not change their encapsulation efficiency. The encapsulation efficiency of all heated sodium caseinate‐glucose‐glucose syrup mixtures was high, as indicated by the low solvent‐extractable fat in powder (<2% powder, w/w). However, increasing the severity of the heat treatment of the sodium caseinate‐glucose‐glucose syrup mixtures reduced the susceptibility of the fish oil powder to oxidation. The increased protection afforded to fish oil in powders by increasing the temperature‐time treatment of protein‐carbohydrate mixtures before emulsification and drying was observed irrespective of the protein (sodium caseinate, whey protein isolate, soy protein isolate, or skim milk powder) and carbohydrate (glucose, glucose/dried glucose syrup, or oligosaccharide/dried glucose syrup) sources used in the formulation. Maillard reaction products produced by heat treatment of aqueous protein‐carbohydrate mixtures were effective for protecting microencapsulated fish oil and other oils (evening primrose oil, milk fat) from oxidation.     

Denaturation of Lactate Dehydrogenase During Spray-Drying of Bovine Plasma

Denaturation kinetics of lactate dehydrogenase (LDH) during spray-drying and heating of bovine plasma showed the free energy of denaturation was constant about 100 kJ/mol. Protein denaturation was investigated by polyacrylamide gel electrophoresis and solubility. At low outlet drying temperatures LDH denaturation was low and powders were completely soluble. At high outlet temperatures LDH denaturation was high and associated with powder insolubility. Electrophoretic patterns of dried samples showed differences from raw plasma at high outlet temperatures, perhaps due to production of soluble aggregates. However, LDH was not a general index of heat denaturation in spray-drying.     

Effects of feed composition,protein denaturation and storage of milk serum protein/lactose powders on lactosylation

During whey powder production, the feed is subjected to several heat treatments which can cause lactosylation of proteins. In this study, lactosylation of whey proteins was evaluated in spray-dried powders before and after storage by varying the native protein fraction as well as the serum protein/lactose ratio in the powders. The lactosylation of native α-lactalbumin and β-lactoglobulin in the powders before storage was not affected to a large extent by the protein denaturation or if the feed had been heat treated in a high or low lactose environment. After storage (relative humidity of 23.5%, 30 °C, 25 days), the kinetic of lactosylation tended to increase with increasing native protein fraction and bulk protein content in the powders. An explanation could be that proteins dissolved in the lactose glassy structure might have a lower reactivity, while proteins present in the protein glassy structure with dissolved lactose may display higher lactosylation reactivity.     

Heat-Induced Aggregation Properties of Whey Proteins as Affected by Storage Conditions of Whey Protein Isolate Powders

The control of storage as any other manufacturing steps of dairy powders is essential to preserve protein functional properties. This study aimed to determine the effects of different storage conditions on both protein denaturation and protein lactosylation in whey protein isolate (WPI) powder, and also on heat-induced aggregation. Two different storage temperature conditions (20 and 40 °C) were studied over 15 months. Our results showed that protein lactosylation progressively increased in WPI powders over 15 months at 20 °C, but heat-induced aggregation properties did not significantly differ from non-aged WPI. On the other hand, powders presented a high level of denaturation and aggregation at 40 °C from the first 2 weeks of storage, involving first protein lactosylation and then aggregation in the dry state. This was correlated with an increasing Browning Index from 15 days of storage. These changes occurred with a decrease in aggregate size after heat treatment at 5.8?≤?pH?≤?6.6 and modification of heat-induced aggregate shapes.     

High-performance liquid chromatographic determination of furfural compounds in infant formulas during full shelf-life

In order to evaluate the extent of the Maillard reaction in adapted and follow-up infant formulas (IF), a study was made of the evolution of furfural compound (2-furaldehyde, 5-hydroxymethyl-2-furfuraldehyde, 2-furylmethylketone and 5-methyl-2-furaldehyde) in these products, along with their relation to available lysine during the shelf-life period (two years at 20 and 37 °C).Total and free furfural contents were measured by RP-HPLC and UV detection, heating or not the sample in boiling water to free the furfurals bound to proteins and the furfurals formed from precursors. Only 2-furylmethylketone and 5-hydroxymethyl-2-furfuraldehyde were detected. Adapted and follow-up IF showed similar behaviour during shelf-life, with a significant increase in furfural compound contents at the end of the storage period that was more marked at 37 °C than at 20 °C. In both IF, a correlation was obtained between furfural contents and the cubic time variable, which explains the irregular increase of these compounds over time, and between available lysine and furfural compounds in the second storage year – indicating the Maillard reaction to be in an advanced stage.Results obtained indicate that under storage conditions furfural content is a useful indicator of advanced Maillard reaction stages.     

Enhancement of emulsifying properties of whey proteins by controlling spray-drying parameters

Whey protein concentrate is the main source of globular proteins in food products which are principally used as emulsifying, foaming and gelling ingredients. These whey proteins are commonly used in powder form obtained by a spray-drying process. It is well known that β-lactoglobulin, the major protein component in whey, is greatly affected by heat treatments, with consequences on its adsorption properties at fluid–fluid interfaces. This study concerned four whey protein powders obtained using spray-drying at four different air inlet temperatures (from 170 to 260 °C), leading to different levels of protein solubility, denaturation and end-use properties. After evaluation of the protein denaturation by HPLC, the emulsifying properties were studied through particle size parameters and rheological properties in relation with spray-drying parameters. Our results indicated that oil-in-water emulsions, stabilized by 5% (w/w) protein samples, exhibited a shear-thinning flow behaviour, and the harsher the spray-drying conditions (the higher the protein denaturation), the less viscous were the emulsions. The apparent viscosity of emulsions measured at 20 °C and 50 s⁻¹ shear rate was around 0.08 Pa s when containing whey proteins before drying, and around 0.05–0.018 Pa s after drying at air inlet temperatures from 170 to 260 °C. These differences in emulsion rheological properties were related to particle size effects, in regards to analysis of particle size distributions which showed a finer emulsion according to spray-drying intensity. Our results will be presented and discussed in terms of optimization of spray-drying process relative to globular protein surface activity.     

Effects of heating on the secondary structure of proteins in milk powders using mid-infrared spectroscopy

Milk powder is an important source of protein for adults and children. Protein is very sensitive to heat, which may influence people’s usage of nutrients in milk powder. In this study, we describe the temperature-induced secondary structure of protein in milk powders. In this study, whole milk powder containing 24% protein and infant formula containing 11% protein were heated from 25 to 100°C. Attenuated total reflectance (ATR) spectra in the mid-infrared range 400–4,000 cm^?1 were used to evaluate the heat effect on the secondary structure of protein in these 2 milk powders. The spectral changes as a function of temperature were maintained by difference spectra, second-derivative spectra and Gauss curve-fitted spectra. The secondary structures of protein in the whole milk powder began to change at 70°C and in the infant formula at 50°C. The β-sheet and β-turn structures in the whole milk powder both decreased in the range of 70 to 85°C, whereas α-helix structures increased. The loss of β-sheet and β-turn may contribute to the formation of α-helix in the whole milk powder. In infant formula powder, the β-sheet structure showed a decrease and then increase, whereas the β-turn structure showed an increase and then decrease in the range of 50 to 75°C, and no change was found for α-helix structures. This implies that heating may induce the transformation from β-sheet to β-turn. Overall, whole milk powder had better temperature stability than infant formula powder, probably because of the lower content of lipid in the former than in the latter. These results help us understand the thermal stability of protein in milk powder.     

Optimising water activity for storage of high lipid and high protein infant formula milk powder using multivariate analysis

High lipid and high protein infant formula milk powders were stored at water activity of 0.11, 0.33 and 0.53 for up to fourteen weeks at 40 °C to investigate the effect of storage water activity on physicochemical properties and formation of volatiles to thereby recommend optimal storage water activity conditions. Water activity of the powders was determined during storage together with surface colour, glass transition temperature combined with dynamic headspace sampling followed by gas chromatography/mass spectrometry. The principal component analysis (PCA) showed that the optimal water activity for storage of high lipid infant formula milk powder, for which lipid oxidation was found to be the critical quality parameter, is a_w = 0.33 with lowest lipid oxidation, while for high protein infant formula milk powder, for which protein degradation was found to be the critical quality parameter, a_w = 0.11 is optimal to limit formation of Maillard reaction products.     

Storage stability,color kinetics and morphology of spray-dried soursop (Annona muricata L.) powder: effect of anticaking agents

Soursop is a tropical fruit that undergoes postharvest deterioration rapidly. Conversion into powder is an ave nue to value-add the fruit as it helps to reduce postharvest losses. Although powder production is not complicated, studies have shown that caking is a common problem often associated with fruit powders. Thus, an addition of a food additive is needed to improve the storage stability of powders. In this study, soursop powder was produced by spray-drying an enzyme-liquefied soursop puree incorporated with either tricalcium phosphate (TCP) or calcium silicate (CS), at three different concentrations (0.5, 1.0, and 1.5% w/w). The control was considered powder without the addition of anticaking agent. Storage stability of the powder packed in aluminum-laminated polyethylene (ALP) pouches was examined at conventional (25 ± 1°C) and accelerated (38 ± 1°C) temperatures for 91 days until lumpiness was observed. Statistical analysis showed that the addition of anticaking agent significantly (p ≤ 0.05) improved the process yield of powder (7.2%). The moisture content, water activity, density, and water solubility index of the powder were significantly affected by storage time, storage temperature, and concentration of the anticaking agents. The critical moisture content, X_c, for control and powder incorporated with either TCP or CS was 0.07 g H₂O/g ds. The total color difference (ΔE) of the powder increased throughout the storage period, followed by a zero-order kinetic reaction. Kinetics-derived Arrhenius model showed that the activation energy (Ea) of color change ranged between 6.5 and 17.3 kJ/mol. Scanning electron microscopy showed that the freshly spray-dried powder was composed of spherical particles with smooth surfaces but these particles tended to agglomerate and form liquid bridges after storage for 91 days. Overall, TCP and CS exhibited a protective effect by lowering moisture adsorption and improved the glass transition temperature of the powder.     

Quality Assurance of Model Infant Milk Formula Using a Front-Face Fluorescence Process Analytical Tool

Front-face fluorescence spectroscopy (FFFS) was evaluated as a quality assurance process analytical technology (PAT) tool for infant milk formula (IMF) manufacture. Batches of first-stage IMF (60:40 whey protein:casein ratio) powder were produced with protein:fat:lactose ratios of 1.3:3.6:7.3, differing only in heat treatment applied prior to spray drying (72, 95, or 115 °C for 15 s). Each IMF powder was stored at 15?±?2 °C and 37?±?2 °C and analyzed at months 0, 3, 6, and 12. Partial least squares (PLS) models were developed for IMF in both powder and liquid states using FFFS spectra to predict pre-drying heat treatment temperature, soluble protein content, and storage time. Models developed using tryptophan emission spectra for IMF powder predicted storage time, pre-drying heat treatment temperature, and soluble protein content with RMSECV values of 0.3 months, 8.3 °C, and 1.01 g protein/100 g powder, respectively. IMF powders were rehydrated to 13% total solids and analyzed using the vitamin A emission spectra. Models developed for rehydrated IMF predicted storage time and pre-drying heat treatment temperature with RMSECV values of 1.5 months and 6.7 °C, respectively. Surface free fats were predicted with an RMSECV range of 0.12–0.20% (w/w of powder) in rehydrated IMF. PLS discriminant analysis models developed for both powder and liquid IMF samples successfully discriminated for storage temperature. This preliminary study demonstrates the strong potential of FFFS as a PAT tool for IMF quality assurance.     

Effects of the repair treatment on improving the heat resistance of Lactiplantibacillus plantarum LIP-1

To improve the heat resistance of lactobacilli during spray-drying, we first investigated the effect of heat shock and repair treatment on the heat resistance of Lactiplantibacillus plantarum LIP-1, and the specific cell repair mechanism. Compared with control group, the reduction of the strain after the heat treatment (75 °C for 40 s) decreased from 1.05 to 0.36 log CFU/mL (initial cell counts 9.30 log CFU/mL) by heat shock (44 °C for 10 min). The residuals of the strain after heat-treated increased by 0.90 log CFU/mL by heat shock firstly, and then the repair treatment (30 °C for 10 min).During recovery period, the relative content of unsaturated long-chain fatty acids (C18:1n9 & C18:2n6) induced by heat shock proteins increased by 7.0%, and the amount of DnaK protein anchored on the cell membrane increased by 0.17 pg/mL. Cell membrane damage caused by heat shock was reduced and strain heat resistance was improved.Industrial relevanceOur research found that the repair treatment after heat shock reduced cell membrane damage caused by heat shock, which is a very promising technology for improving the heat resistance of L. plantarum LIP-1. This technology is also expected to be widely used in the preparation of LAB powders by spray-drying technology.     

The influence of enzymatic cross‐linking of proteins on the Maillard reaction in milk

The influence of transglutaminase (TGase) on the Maillard reaction was investigated in skimmed milk samples during heat treatment. TGase‐treated and control samples were heated at 80, 120 and 140 °C for 1, 5, 15, 30, 40 and 60 min. Compared with the TGase‐treated samples heated at 80 and 120 °C, the sample heated at 140 °C showed a larger decrease in furosine concentration. It was also found that TGase did not affect the formation of hydroxymethylfurfural and lactulose at 120 °C, whereas their concentrations increased in the presence of TGase at 140 °C. It was concluded that blockage of lysine residues via enzymatic cross‐linking of milk proteins had a limited effect on the Maillard reaction.     

Spray-Drying of Antioxidant-Rich Blueberry Waste Extracts; Interplay Between Waste Pretreatments and Spray-Drying Process

This study aimed to establish an efficient route for converting blueberry waste material (BWM) into antioxidant-rich powders. Extracts were produced from BWM by an aqueous method using water acidified with citric acid, in the absence or presence of Pectinex Ultra SP-L and Cellubrix. All BWM extracts contained antioxidants including phenolic acids, anthocyanins, and flavonoids (total phenolic content (TPC) 3655–4369 mg gallic acid equivalent (GAE) and total anthocyanin content (TAC) 219–296 mg cyanidin-3-glucoside equivalents (CyGE) per 100 g dry extract). Extractions at 50 °C yielded higher TPC and TAC but lower vitamin C and pectin contents than extractions at 20 °C. Spray-drying BWM extracts produced at 50 °C (no enzymatic treatments) and an encapsulant (alginate or inulin) at an inlet temperature 150 °C and feed temperature 50 °C yielded powders with desired dark purplish blue color, water activity (0.25–0.33), flowability, reconstitution time (23–46 s in water or milk), TPC (25–30 mg GAE/g), TAC (17–20 mg CyGE/g), storage stability, and Bifidobacterium-boosting properties. Enzymatic pretreatments of BWM did not confer any advantages in preserving antioxidants in powder products, suggesting that some intrinsic BWM components (e.g., pectins) may play an important role in the encapsulating process. The use of alginate as the encapsulant/drying aid afforded higher powder yields, superior protection of antioxidants, better stability over a prolonged storage or elevated temperature storage, greater retention of TPC/TAC under simulated gastrointestinal conditions, and greater Bifidobacterium-boosting effects, compared to powders prepared using inulin. Thus, simple aqueous extraction methods and spray-drying technology hold enormous promise for producing antioxidant-rich powders from blueberry processing by-products or waste.     

Evolution of available lysine and lactose contents in supplemented microencapsulated fish oil infant formula powder during storage

In this work we report the evolution of available lysine, lactose and lipid hydroperoxide contents as indicators of food quality and stability of two types of infant formula powder stored at 25° and 37 °C for 12 months. The first type was supplemented with microencapsulated fish oil (MFO), made of little powder particles in a food starch‐coated matrix of caseinate and saccharose to prevent the oxidation of polyunsaturated fatty acid (PUFA). The second type was not supplemented and was used for reference. MFO might not be stable during storage and affect negatively the quality of the formula in two ways: by oxidation of PUFA, which may also easily react with lysine upon oxidation, blocking lysine, or by hydrolysis of saccharose, producing reducing sugars and increasing the Maillard reaction. Slight changes were observed in lysine and lactose evolution. By comparing the two formulae, this study shows that the MFO material did not negatively affect the studied parameters, indicating therefore acceptable stability in the conditions tested.     

Effects of milk heat treatment and solvent composition on physicochemical and selected functional characteristics of milk protein concentrate

Milk protein concentrate (MPC) powders (～81% protein) were made from skim milk that was heat treated at 72°C for 15 s (LHMPC) or 85°C for 30 s (MHMPC). The MPC powder was manufactured by ultrafiltration and diafiltration of skim milk at 50°C followed by spray drying. The MPC dispersions (4.02% true protein) were prepared by reconstituting the LHMPC and MHMPC powders in distilled water (LHMPC_w and MHMPC_w, respectively) or milk permeate (LHMPC_p and MHMPC_p, respectively). Increasing milk heat treatment increased the level of whey protein denaturation (from ～5 to 47% of total whey protein) and reduced the concentrations of serum protein, serum calcium, and ionic calcium. These changes were paralleled by impaired rennet-induced coagulability of the MHMPC_w and MHMPC_p dispersions and a reduction in the pH of maximum heat stability of MHMPC_p from pH 6.9 to 6.8. For both the LHMPC and MHMPC dispersions, the use of permeate instead of water enhanced ethanol stability at pH 6.6 to 7.0, impaired rennet gelation, and changed the heat coagulation time and pH profile from type A to type B. Increasing the severity of milk heat treatment during MPC manufacture and the use of permeate instead of water led to significant reductions in the viscosity of stirred yogurt prepared by starter-induced acidification of the MPC dispersions. The current study clearly highlights how the functionality of protein dispersions prepared by reconstitution of high-protein MPC powders may be modulated by the heat treatment of the skim milk during manufacture of the MPC and the composition of the solvent used for reconstitution.     

The Influence of Drying Process Conditions on the Physical Properties,Bioactive Compounds and Stability of Encapsulated Pumpkin Seed Oil

In this study, the influence of encapsulation process conditions on the physical properties and chemical composition of encapsulated pumpkin seed oil was investigated. Four variants of encapsulated oil were prepared: spray-dried non-homogenized emulsions at the inlet temperatures of 180 and 130 °C, spray-dried homogenized emulsion at the inlet temperature of 130 °C, and freeze-dried homogenized emulsion. The emulsion was prepared by mixing 10.6% oil with 19.8% wall materials (15.9% maltodextrin + 0.5% guar gum + 3.9% whey protein concentrate) and 69.6% distilled water. The quality of encapsulated pumpkin seed oil was evaluated by encapsulation efficiency, surface oil, total oil and moisture contents, flowing properties, color, and size. Additionally, fatty acid composition, pigment characteristics, and the content of bioactive compounds (tocopherols, squalene, and sterols) were determined. Changes of these components after the encapsulation process in comparison to the control pumpkin seed oil were considered as stability parameters. The highest encapsulation efficiency was obtained by spray-drying at the inlet temperature of 130 °C. Generally, the spray-drying process had a positive effect upon the physical parameters of encapsulated pumpkin seed oil but results were dependent on process conditions. The higher inlet temperature generated more surface oil, but capsules obtained at the lower temperature were greater in size and more deformed. Although freeze-drying proceeded at a very low temperature, the powder obtained with this technique was characterized by the highest bioactive compound losses (with the exception of sterols) and the lowest stability. The homogenization process applied before spray-drying affected greater polyunsaturated fatty acid, squalene, and pigment degradation. In conclusion, results of the study showed that the spray-drying non-homogenized emulsion was a more recommendable technique for the encapsulation of pumpkin seed oil because of smaller changes of native compounds and better oxidative stability.     

Immunochemical Studies on the Denaturation of Ovalbumin Stored with Glucose

The ovalbumin denaturation induced by Maillard reaction with glucose was investigated by immunochemical methods. The storage for either 2 or 10 days at 50°C and 65% relative humidity decreased the maximum immunoprecipitation to 90 and 80% of that by native protein, respectively. Ten day-stored ovalbumin was separated into two fractions with antigenicity (fr-II) and without (fr-I) by the immunoaffinity chromatography of antiovalbumin-coupled Sepharose 4B. The circular dichroism (CD) analysis showed that fr-II, containing amino groups in almost the same amount as fr-I, retained a large amount of ordered structure. Ovalbumin molecules were presumably not denatured by only the modification of amino groups with glucose in an early stage of Maillard reaction.     

Application of front-face fluorescence spectroscopy as a tool for monitoring changes in milk protein concentrate powders during storage

This study investigated the feasibility of front-face fluorescence spectroscopy (FFFS) to predict the solubility index and relative dissolution index (RDI) of milk protein concentrate (MPC) powders during storage. Twenty MPC powders with varying protein contents from 4 different commercial manufacturers were used in this study. The MPC powders were stored at 2 temperatures (25 and 40°C) for 0, 1, 2, 4, 8, and 12 wk. The front-face fluorescence spectra of tryptophan and Maillard products were recorded and analyzed with chemometrics to predict solubility of MPC powders. The similarity maps showed clear discrimination of the MPC samples stored at 25 and 40°C. Partial least squares regression models were developed using the fluorescence spectra of tryptophan and Maillard products to predict the solubility index and RDI measurements of MPC powders, and the prediction models were validated using an independent test set. Coefficients of determination (R²) of 0.76, 0.84, and 0.68 were obtained between fluorescence spectra (tryptophan emission, Maillard emission, and Maillard excitation, respectively) and solubility index. The R² values for the RDI predictions were 0.58 and 0.60 for the data set of tryptophan emission and Maillard emission, respectively. The ratio of prediction error to standard deviation was >2 for Maillard emission fluorescence spectra and solubility index measurements, indicating good practical utility of the partial least squares regression prediction models. The results indicated that the solubility and dissolution behavior of MPC powders were related to their protein content and storage conditions that could be measured using FFFS. Hence, FFFS can be used as a rapid nondestructive analytical technique to predict the solubility and dissolution characteristics of MPC powders.     

A standard set of testing methods reliably enumerates spores across commercial milk powders

Contamination of dairy powders with sporeforming bacteria is a concern for dairy processors who wish to penetrate markets with stringent spore count specifications (e.g., infant powders). Despite instituted specifications, no standard methodology is used for spore testing across the dairy industry. Instead, a variety of spore enumeration methods are in use, varying primarily by heat-shock treatments, plating method, recovery medium, and incubation temperature. Importantly, testing the same product using different methodologies leads to differences in spore count outcomes, which is a major issue for those required to meet specifications. As such, we set out to identify method(s) to recommend for standardized milk powder spore testing. To this end, 10 commercial milk powders were evaluated using methods varying by (1) heat treatment (e.g., 80°C/12 min), (2) plating method (e.g., spread plating), (3) medium type (e.g., plate count milk agar), and (4) incubation time and temperature combinations (e.g., 32°C for 48 h). The resulting data set included a total of 48 methods. With this data set, we used a stepwise process to identify optimal method(s) that would explain a high proportion of variance in spore count outcomes and would be practical to implement across the dairy industry. Ultimately, spore pasteurized mesophilic spore count (80°C/12 min, incubated at 32°C for 48 h), highly heat resistant thermophilic spore count (100°C/30 min, incubated at 55°C for 48 h), and specially thermoresistant spore enumeration (106°C/30 min, incubated at 55°C for 48 h) spread plating on plate count milk agar were identified as the optimal method set for reliable enumeration of spores in milk powders. Subsequently, we assessed different powder sampling strategies as a way to reduce variation in powder spore testing outcomes using our recommended method set. Results indicated that 33-g composite sampling may reduce variation in spore testing outcomes for highly heat resistant thermophilic spore count over 11-g and 33-g discrete sampling, whereas there was no significant difference across sampling strategies for specially thermoresistant spore enumeration or spore pasteurized mesophilic spore count. Finally, an interlaboratory study using our recommended method set and a modified method set (using tryptic soy agar with 1% starch) among both university and industry laboratories showed increased variation in spore count outcomes within milk powders, which not only was due to natural variation in powders but also was hypothesized to be due to technical errors, highlighting the need for specialized training for technicians who perform spore testing on milk powders. Overall, this study addresses challenges to milk powder spore testing and recommends a method set for standardized spore testing for implementation across the dairy industry.     

Accurate quantification of thermophilic spores in dairy powders

Internationally, there are no official guidelines for the quantification of thermophilic spores in dairy products, which leads to variations in applied methodology. In this study, we assess the heat sensitivity of thermophilic spores, vegetative cells grown under laboratory conditions and spores in German dairy powders to determine appropriate heating conditions for accurate quantification of total thermophilic spores. The heat inactivation effect (80–95 °C) is limited for spores of Anoxybacillus flavithermus and Geobacillus stearothermophilus grown under laboratory conditions. However, for spores originating from whey, whey powder and skimmed milk powder (mostly identified as A. flavithermus), a different trend was observed; spore counts continuously reduced when heating time and temperature increased (80–98 °C, 10–30 min). The results indicate that data obtained using laboratory cultures cannot be extrapolated to commercial powders, and in this case, applying temperatures above 80 °C leads to an underestimation of spore counts in dairy powders.