Reconstituted Infant Formula Research Articles

Rapid safety assessment of reconstituted infant formula using electrical impedance analysis

A rapid method to assess freshness is crucial for the safe handling of reconstituted infant formula (RIF) and prevention of food-borne illnesses in infants. This study explored the use of electrical impedance measurement (EIM) at a constant frequency for real-time freshness evaluation of RIF. Initial electrical impedance of 89.16 ± 0.47 Ω decreased to 74.29 ± 0.23 Ω within 48 h at room temperature (20 °C) storage. Under temperature abuse conditions (30 °C), the electrical impedance rapidly dropped from 75.48 ± 0.52 Ω to 60.15 ± 4.76 Ω within 18 h, indicating more rapid spoilage. Notable changes in the electrical impedance were observed during temperature abuse. Empirical model analysis revealed a strong positive correlation between electrical impedance and conventional freshness parameters such as pH, protein, and microbial growth. This study demonstrates the potential of EIM for the rapid detection of freshness changes in RIF, offering valuable insights into the prevention of food-borne illnesses in infants.

Transcriptomic analysis reveals antibacterial mechanism of probiotic fermented Portulaca oleracea L. against Cronobacter sakazakii and application in reconstituted infant formula

Cronobacter sakazakii is a foodborne pathogen, and the use of effective and non-hazardous bacteriostatic agents to manage C. sakazakii infection has garnered attention. Portulaca oleracea L. is a food plant with several pharmaceutical properties. However, the products of kombucha-fermented P. oleracea (FP) have been scarcely studied with respect to their metabolite profiles and for their effects against food-borne pathogens. Therefore, in this study, the chemical and microbiological composition and inhibitory effects of FP against C. sakazakii were evaluated. The activities and molecular mechanisms of FP against C. sakazakii were investigated for the first time using transcriptomic and physiological experiments. Komagataeibacter was the most abundant bacterium in fermentation broth (>79%), and chlorogenic and acetic acids were the most abundant phenolics and organic acids in fermentation products. Transcriptomic analysis showed that FP induced significant changes in C. sakazakii as demonstrated by the differential expression of 506 genes. The genes that exhibited differential expression were primarily involved in ATP-related energy metabolism, cell membrane structure, protein biosynthesis, amino acid transport, and metabolism. These roles suggest multifaceted potential effects including cell membrane damage, protein synthesis limitation, metabolism disorder, reduced virulence factor expression, and reduced cell mobility. FP addition significantly inhibited C. sakazakii growth in PIF. These results provide insights into the anti-C. sakazakii mechanism of FP, which is valuable for its development and application in food safety.

Modelling growth of Bacillus cereus in paneer by one-step parameter estimation.

Bacillus cereus phylogenetic group III and IV strains are commonly associated with food products and cause toxin mediated foodborne diseases. These pathogenic strains have been identified from milk and dairy products, such as reconstituted infant formula and several cheeses. Paneer is a fresh, soft cheese originating from India that is prone to foodborne pathogen contamination, such as by Bacillus cereus. However, there are no reported studies of B. cereus toxin formation in paneer or predictive models quantifying growth of the pathogen in paneer under different environmental conditions. This study assessed enterotoxin-producing potential of B. cereus group III and IV strains, isolated from dairy farm environments, in fresh paneer. Growth of a four-strain cocktail of toxin-producing B. cereus strains was measured in freshly prepared paneer incubated at 5-55°C and modelled using a one-step parameter estimation combined with bootstrap re-sampling to generate confidence intervals for model parameters. The pathogen grew in paneer between 10 and 50°C and the developed model fit the observed data well (R2=0.972, RMSE=0.321 log10CFU/g). The cardinal parameters for B. cereus growth in paneer along with the 95% confidence intervals were: μopt 0.812 log10CFU/g/h (0.742, 0.917); Topt is 44.177°C (43.16, 45.49); Tmin is 4.405°C (3.973, 4.829); Tmax is 50.676°C (50.367, 51.144). The model developed can be used in food safety management plans and risk assessments to improve safety of paneer while also adding to limited information on B. cereus growth kinetics in dairy products.

Selenium in selected samples of infant formulas and milk commercialized in Belgium and Brazil: Total content, speciation and estimated intake

Total selenium (Se) and Se species concentrations were determined in 50 infant formulas and milk samples commercialized in Brazil and Belgium. Infant formula categories were starter, follow-up, specialized and plant-based (soy and rice), while milk samples included whole, skimmed, semi-skimmed and plant-based products. Total Se content was determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), after microwave digestion. An enzymatic extraction method was applied to evaluate the Se species, mostly selenomethionine (SeMet), Se(IV) and Se(VI), through High Performance Liquid Chromatography coupled to ICP-MS (LC-ICP-MS). Starters and follow-up samples presented the highest total Se concentrations and values up to 30 µg/kg were observed in the reconstituted product. The lowest level (below the LOQ = 10 µg/kg) was verified in an anti-regurgitation specialized formula. The relative agreement between the measured total Se and the Se content declared on the label varied from 55 % to 317 %. Concentrations in infant formulas were not markedly different from concentrations in milk except for rice and oat milk samples that showed values below the LOQ. SeMet was the main species found in milks, while in infant formulas the species concentrations varied according to the product. The daily intake (DI) of Se via infant formula consumption was calculated and compared with the Adequate Intake (AI) value and the Dietary Reference Intake (DRI) established by the EFSA NDA Panel and ANVISA, respectively. Estimated maximum intakes of total Se obtained for reconstituted infant formula were 40.6 mg/day, corresponding to 400 % and 202 % of the DRI and AI, respectively.

Characterization of the nitrite production of mesophilic spore-forming bacteria during the handling of reconstituted infant formula

The microbiological safety of reconstituted infant formula (RIF) has focused on infectious pathogens, whereas the risk of spore-forming bacteria (SFB) has been limited to spoilage and toxin production. This study suggests an underrecognized niche of SFB as nitrite producers during the handling of RIF. The production of nitrite along with the bacterial growth of 133 nitrite-producing SFB isolated from infant formula processing environments and end-products (70 mesophiles and 63 thermophiles) under RIF handling conditions were analysed. Most mesophiles (68 out of 70) and two thermophiles showed nitrite production during growth at 30 °C or 40 °C. Vigorous producers of nitrite [Bacillus sp. strains (FHS-PPBM449, 481, 236, 237)] showed a rapid onset of nitrite production (within 4 h). In particular, FHS-PPBM449 (2–3 log CFU/mL) exhibited the shortest onset time (210 min) and a nitrite production level up to 521 µM in RIF with 100 ppm nitrate at 40 °C. Overall, the results of the maximum level of nitrite produced by vigorous nitrite producers indicate that infants can consume more than seven times the acceptable daily intake of nitrite (0.74 mg for 12-month-old infants with an average body weight), even via a single feeding of RIF. An analysis of the relationship of the onset time of nitrite production with the bacterial concentration based on predictive models suggests that the growth of SFB up to 5–6 log CFU/mL is regarded as a prerequisite for nitrite production. This study revealed an underreported source of nitrite from RIF handling conditions, and the rapid onset of a high level of nitrite production from SFB should be the major target in the establishment of intervention strategies against nitrite as a microbial risk.

Impact of bovine lactoferrin fortification on pathogenic organisms to attenuate the risk of infection for infants

Cronobacter and Pseudomonas spp. are pathogenic organisms that are associated with neonatal morbidities such as bacteremia, sepsis, necrotizing enterocolitis (NEC), and infant meningitis. Lactoferrin (Lf) is a known bactericidal component of fresh human milk. Infants receiving formula or pasteurized donor milk however may not be receiving lactoferrin at same concentration as mother's own milk, so it is beneficial to understand an exogenous role for dairy bovine lactoferrin (bLf). Our aim was to investigate the potential for bLf to provide a novel way to inhibit the growth of these harmful organisms in infant feeding. Subinhibitory doses, Disc-diffusion assay, Minimum Inhibitory Concentrations (MIC), Minimum Bactericidal Concentrations (MBC), and challenge experiments in powder formula were used to investigate the effects of bLf on sepsis-causing bacteria such as C. muytjensii (ATCC-51329), C. sakazakii (ATCC-12868), C. sakazakii (ATCC-9027), P. aeruginosa (ATCC-19429), and P. aeruginosa (ATCC-9027). MIC and MBC of bLf in the range of 12.5–31.25 μM were sufficient to achieve a 3 log reduction of Cronobacter in nutrient broth (P < 0.0001). Similarly, minimum concentrations of 43.75–118.75 μM bLf against Pseudomonas (P < 0.0001) were demonstrated. After bactericidal concentrations were determined, higher resistant strains such as C. sakazakii (ATCC-12868) and P. aeruginosa (ATCC-19429) were chosen as ideal candidates for the bLf supplementation challenge studies. The bLf reduced the C. sakazakii (ATCC-12868) by 3.3 log at 35 °C, 2.8 log at 23 °C, and 1.9 log at 4 °C (P < 0.0001), whereas P. aeruginosa (ATCC-19429) showed 2.4 log reduction at 35 °C, 2.8 log at 23 °C (P < 0.0001), and 1.8 log at 4 °C (P < 0.01). Results indicated that bLf could effectively inactivate the sepsis-causing organisms in reconstituted infant formula and in bacterial growth media. Fortification of infant formula with bLf may address the problems of spoilage/contamination issues and provide a safety measure for feeding infants without mother's own milk.

Inactivation of Shigella flexneri by 405-nm Light-Emitting Diode Treatment and Possible Mechanism of Action.

Shigella flexneri, a common Gram-negative foodborne pathogen, is widely distributed in fresh-cut fruits and vegetables, unpasteurized milk, and food processing environments. The aims of this study were to evaluate the antibacterial effects of 405-nm light-emitting diode (LED) treatment on S. flexneri and to investigate the possible mechanism. The results showed that LED irradiation (360 min) reduced the number of S. flexneri in phosphate-buffered saline by 3.29 log colony-forming unit (CFU)/mL (initial bacterial count: 6.81 log CFU/mL). The cells in reconstituted infant formula, cells on fresh-cut carrot slices, and biofilm-associated cells on stainless steel surfaces were reduced by 1.83 log CFU/mL, 7.00 log CFU/cm2, and 4.35 log CFU/cm2 following LED treatment for 360, 120, and 120 min, respectively. LED treatment damaged both DNA and cell wall of S. flexneri and changed cell morphology and cell membrane permeability. In addition, LED treatment decreased total cell protein concentration of S. flexneri. These results indicated that 405-nm LED treatment effectively controlled S. flexneri contamination of foods and food contact surfaces and that the bacterial inactivation may be the result of damage to multiple cellular components. These findings highlight the potential of LED technology in controlling S. flexneri during food processing, storage, and preparation.

Antimicrobial Activity and Action Mechanism of Thymoquinone against Bacillus cereus and Its Spores.

In this study, thymoquinone (TQ), a natural active substance, was investigated for its antibacterial activity against Bacillus cereus, and its inhibitory effect on B. cereus in reconstituted infant formula (RIF) was evaluated. In addition, the inhibitory effect of TQ on B. cereus spore germination was explored. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of TQ against eight B. cereus strains ranged from 4.0 to 8.0 μg/mL, whereas B. cereus treated with TQ displayed a longer lag phase than the untreated control. TQ exerted a good bactericidal effect on B. cereus in Luria–Bertani broth. In addition, TQ obviously reduced the intracellular ATP concentration of B. cereus, which caused depolarization of the cell membrane, increased the intracellular reactive oxygen species level, impaired the cell morphology, and destroyed proteins or inhibited proteins synthesis. This provides a mechanism for its bacteriostatic effect. TQ also inactivated B. cereus growth in RIF. Moreover, reverse transcription–quantitative polymerase chain reaction illustrated that TQ downregulated the transcription of genes related to hemolysin, non-hemolytic enterotoxin, enterotoxin, and cytotoxin K. Meanwhile, TQ displayed the ability to inhibit the germination of B. cereus spores. These findings indicate that TQ, as an effective natural antimicrobial preservative, has potential applications in controlling food contamination and foodborne diseases caused by B. cereus.

SdiA plays a crucial role in stress tolerance of C. sakazakii CICC 21544

This study aimed to select for the quorum sensing receptor protein of C. sakazakii CICC 21544, and then evaluate the role of the receptor protein in stress tolerance. SdiA was identified as the receptor by sequence alignment. C. sakazakii CICC 21544 wild type (WT), the sdiA mutant strain (ΔsdiA), and the sdiA complemented strain (sdiA+) were subjected to heat treatment at 55 °C in tryptic soy broth (TSB) or reconstituted infant formula (RIF) and the results suggested that sdiA facilitated C. sakazakii to withstand thermal stress both in TSB and RIF. Similarly, the survival rate of ΔsdiA was significantly lower than that of WT and sdiA+ under osmotic pressure of 12% NaCl or desiccation conditions. Acid tolerance assay showed that loss of sdiA decreased the ability of C. sakazakii to grow in simulated gastric fluid. The survivability of the three strains under combined stress conditions was also evaluated in this study. After heating, evaporation, and drying stresses, ΔsdiA was undetectable, while WT and sdiA+ survived the treatments. This study demonstrates that sdiA contributes to the survival of C. sakazakii under different environmental stresses, and provides a basis for the sdiA-targeted inhibition of C. sakazakii in food.

Synergistic effect of citral and carvacrol and their combination with mild heat against Cronobacter sakazakii CICC 21544 in reconstituted infant formula

The combined effects of four substances, carvacrol, citral, thymol and caprylic acid, on the growth of Cronobacter sakazakii CICC 21544 were evaluated. Among the six combinations, only the combination of citral and carvacrol demonstrated a synergistic effect. This combination had a stronger growth inhibition effect than treatment with citral or carvacrol alone, which led to more portions of cells in the propidium iodide (PI) fluorescent region and caused more severe cell damage. Citral and carvacrol also showed promising and potent antibiofilm activity against C. sakazakii, which was evaluated using crystal violet assay, field emission scanning electron microscopy (FESEM) and qRT-PCR. Mild heat treatment combined with citral and carvacrol at a concentration of 2 or 3 MIC completely eradicated C. sakazakii in reconstituted infant formula. Moreover, the combination at 2 MIC had no significant effect on the color and aroma scores of reconstituted infant formulae. The combination of citral and carvacrol could potentially be developed as an alternative or supplemental agent to reduce infections caused by C. sakazakii in reconstituted infant formula.

Use and understanding of labelling information when preparing infant formula: Evidence from interviews and eye tracking

There are various risks associated with incorrect preparation and storage of infant formula, including microbiological hazards. Preparing and storing reconstituted infant formula correctly can reduce potential risks. The product label on infant formula is often the main source of information for caregivers on the correct handling of infant formula. Caregivers’ ability to understand and follow preparation and storage instructions is, therefore, of high importance in the safe use of infant formula. This study aims to increase understanding of how Australian caregivers perceive, interpret and use mandatory and voluntary “on-pack” label information when preparing and storing infant formula. An eye-tracking task requiring caregivers (n = 30) to prepare an unfamiliar infant formula product while wearing Tobi Pro 2 Glasses revealed that almost all caregivers look at the preparation instructions (93%), though fewer look at the warning advice (43%) and storage instructions (27%). Findings from retrospective think-aloud and in-depth interviews conducted immediately after the eye-tracking task, revealed that while preparation instructions are generally understood, they are not always adhered to, with most caregivers making modifications for convenience. Lack of awareness and low perceived risk to the infant’s health were other reasons for non-adherence. These findings suggest that mandated food-safety elements on infant formula products need to be more noticeable, clearer and more specific with respect to potential infant health risks associated with non-adherence, to ensure safe preparation and storage by all caregivers. These findings will be used to inform a review of the labelling requirements for infant formula products.

Inhibition of Cronobacter sakazakii in reconstituted infant formula using triglycerol monolaurate and its effect on the sensory properties of infant formula

Cronobacter sakazakii (C. sakazakii) is an opportunistic foodborne pathogen in infant formula. This study was designed to explore the inhibitory effect of TGML on C. sakazakii in reconstituted infant formula (RIF). Firstly, the growth curve of C. sakazakii in RIF treated by TGML and the effect of different temperatures (4, 10, 21, 30 and 37 °C), pH values (5, 6, 7, 8 and 9) and ionic strengths (25, 50, 100, 200, 400 and 800 mM) on its activity were assessed. The results showed that the inhibitory effect of TGML on C. sakazakii was dose-dependent, and 1, 2 and 5 μg/mL TGML delayed the visible growth of pathogen by 4, 12 and 24 h, respectively. Storage temperature above or below room temperature enhanced the bioactivity of TGML. And a decrease in pH also increased the antibacterial effect of TGML. However, the effect of ionic strength on its activity was not obvious. Subsequently, the antibacterial effect of TGML in physiological gastric acid and simulated gastric juice in vitro was further explored. We found that only 5 μg/mL TGML could inhibit the growth of pathogen below the infectious dose (10,000 CFU in total) in simulated gastric juice during the whole gastric emptying period (3.5–21 h), weaker than its antibacterial effect in physiological gastric acid and room temperature culture. Finally, the effect of TGML and the above environmental factors on the color and aroma of infant milk was evaluated by a 12-person panel. The results revealed that TGML did not affect the sensory flavor of milk, and the color and odor scores of infant milk under different environmental conditions did not show any significant differences. Therefore, it is concluded that TGML has a good inhibitory effect on C. sakazakii in RIF and a high sensory acceptability for consumers. Adjusting the temperature or lowering the pH enhances its bacteriostatic activity. However, the presence of infant gastric juice can impair the bioactivity of TGML. Overall, this study will provide some new ideas for controlling and eliminating the potential risk of C. sakazakii infection during infant feeding.

Evaluation of the GENE-UP®Cronobacter Method for the Detection of Cronobacter Species in Select Foods and Environmental Surfaces: Collaborative Study, First Action 2019.01.

The GENE-UP®Cronobacter assay (Performance Tested MethodSM 081801) is a real-time PCR technology for the rapid detection of Cronobacter species in select foods and environmental surfaces. The purpose of this validation was to evaluate the method's interlaboratory performance and submit the result to AOAC INTERNATIONAL for adoption as a First Action Official MethodSM for the detection of Cronobacter species in select foods and environmental surfaces. The GENE-UP method was evaluated in a multilaboratory study as part of the AFNOR NF VALIDATION certification process (NF102) following ISO 16140-2:2016 using unpaired test portions for one food matrix, reconstituted infant formula containing probiotics. The candidate method was compared to the ISO 22964:2017 reference method. Sixteen participants from fifteen laboratories throughout the European Union participated. Three levels of contamination were evaluated: a noninoculated control level (0 CFU/target test portion), a low contamination level (approximately 2 CFU/target test portion), and a high contamination level (approximately 10 CFU/target test portion). Data from that study were analyzed according to the probability of detection (POD) statistical model as presented in the AOAC validation guidelines. The difference in laboratory POD (dLPODC) values with 95% confidence intervals across collaborators was calculated for each level between the candidate and reference method results and between the candidate presumptive and confirmed results. The dLPODC values with 95% confidence intervals were 0.00 (-0.03, 0.03), -0.08 (-0.19, 0.02), and 0.00 (-0.03, 0.03) for the noninoculated, low, and high contamination levels, respectively. The dLPODC results indicate no significant difference between the candidate method and the reference method or between presumptive and confirmed results for all three levels of contamination. The GENE-UP Cronobacter assay provides industry with a rapid, easy to use method for the rapid detection of Cronobacter in a wide range of products and environmental samples.

Nucleic acid lateral flow immunoassay (NALFIA) with integrated DNA probe degradation for the rapid detection of Cronobacter sakazakii and Cronobacter malonaticus in powdered infant formula

A novel nucleic acid lateral flow immunoassay (NALFIA) system for Cronobacter (C.) sakazakii and C. malonaticus is based on amplification of the rpoB gene in the presence of a heterobifunctional, Cronobacter-specific DNA probe. Partial degradation of this probe during amplification is then detected by lateral flow immunoassay. The NALFIA detected all of the 22 C. sakazakii and 8 C. malonaticus isolates under study, but showed no reaction with other Cronobacter species or non-Cronobacter species. The minimal visual and instrumental detection limits were 104 cfu/ml for both species in buffered peptone water and in reconstituted infant formula. C. sakazakii or C. malonaticus at levels of 100-101 cfu/g in powdered infant formula were reliably detected by NALFI after reconstitution and 24 h incubation at 37 °C. A major advantage of this approach is that the use of an integrated DNA probe provides additional test specificity. Since C. sakazakii and C. malonaticus are by far the most important Cronobacter species occurring in PIF, the novel NALFIA is a promising tool to enhance rapid control of infant formula.

Effect of thymoquinone on the resistance of Cronobacter sakazakii to environmental stresses and antibiotics

Cronobacter sakazakii is a foodborne bacterial pathogen with resistance to a wide range of stress conditions. Here, we investigated the effects of thymoquinone (TQ) on the environmental and antibiotic stress tolerance of C. sakazakii. After determining the subinhibitory concentrations (SICs) of TQ against C. sakazakii, changes in the percent survival of bacteria under heat, acid, desiccation, and hyperosmotic stress following exposure to TQ were investigated in tryptone soya broth (TSB) and reconstituted infant formula (RIF). We also monitored changes in the expression of stress tolerance-associated genes in the TQ-treated bacteria, and used a minimum inhibitory concentration assay to examine changes in the antibiotic sensitivity of C. sakazakii following TQ treatment. SICs of TQ of 200, 400, and 600 μM were selected for use in the assays. TQ-treated C. sakazakii strains showed a significant decrease in survival following exposure to high temperatures (50°C, 55°C, and 60°C), acidic pH (~3.3), high osmotic pressure (aw = 0.81), and desiccation (P < 0.05) compared with untreated controls in both TSB and RIF. TQ treatment also increased the sensitivity of C. sakazakii to ampicillin and cefoxitin. Moreover, real-time quantitative polymerase chain reaction (RT-qPCR) analysis revealed that the transcription levels of 15 genes associated with stress tolerance was downregulated following TQ treatment (600 μM). Therefore, our findings suggest that TQ has a significant negative impact on the stress tolerance of C. sakazakii, and provide a theoretical basis for the practical application of TQ as a natural antimicrobial agent in food production.

Whole Genome Sequencing-Based Comparison of Food Isolates of Cronobacter sakazakii.

Cronobacter sakazakii is an emerging foodborne pathogen, which is linked to life-threatening infections causing septicemia, meningitis, and necrotizing enterocolitis. These infections have been epidemiologically connected to ingestion of contaminated reconstituted powder infant formula. Even at low water activity C. sakazakii can survive for a long time; it is capable of protective biofilm formation and occasionally shows high virulence and pathogenicity even following stressful environmental conditions. Hence it is a challenging task for the food industry to control contamination of food ingredients and products through the entire production chain, since an increasing number of severe food-related outbreaks of C. sakazakii infections has been observed. The seemingly great capability of C. sakazakii to survive even strict countermeasures combined with its prevalence in many food ingredients requires a greater in depth understanding of its virulence factors to master the food safety issues related to this organism. In this context, we present the whole genome sequence (WGS) of two different C. sakazakii isolated from skimmed milk powder (C7) and ready-to-eat salad mix (C8), respectively. These are compared to other, already sequenced, C. sakazakii genomes. Sequencing of the fusA allele revealed that both isolates were C. sakazakii. We investigated the molecular characteristics of both isolates relevant for genes associated with pathogenesis and virulence factors, resistance to stressful environmental conditions (e.g., osmotic and heat), survival in desiccation as well as conducted a comparative genomic analysis. By using multi-locus sequence typing (MLST), the genetic type of both isolates is assessed and the number of unique genes is determined. DNA of C. sakazakii C8 is shown to hold a novel and unique sequence type; the number of unique genes identified in the genomic sequence of C. sakazakii C7 and C8 were 109 and 188, respectively. Some of the determined unique genes such as the rhs and VgrG genes are linked to the Type VI Secretion System cluster, which is associated with pathogenicity and virulence factors. Moreover, seven genes encoding for multi-drug resistance were found in both isolates. The finding of a number of genes linked to producing capsules and biofilm are likely related to the observed resistance to desiccation.

Survival and Environmental Stress Resistance of Cronobacter sakazakii Exposed to Vacuum or Air Packaging and Stored at Different Temperatures.

The aim of this study was to evaluate the survival of Cronobacter sakazakii exposed to vacuum or air packaging, then stored at 4, 10, or 25°C, and the environmental stress resistance of vacuum-packaged or air-packaged bacterial cells were determined by subjecting the cells to reconstituted infant formula at 50°C, in acid (simulated gastric fluid, pH = 3.5), and in bile salt [bile salt solution, 5% (wt/vol)]. A cocktail culture of C. sakazakii desiccated on the bottom of sterile petri plates was air-packaged or vacuum-packaged and then stored at 4, 10, or 25°C for 10 days. The viable cell populations during storage were examined, and the vacuum-packaged and air-packaged cells (stored at 10°C for 4 days) were subsequently exposed to heat, acid, or bile salt. The results show that the populations of vacuum-packaged and air-packaged C. sakazakii were reduced by 1.6 and 0.9 log colony-forming units (CFU)/ml at 4°C and by 1.6 and 1.3 log CFU/ml at 25°C, respectively, in 10 days. At 10°C, significant reductions of 3.1 and 2.4 log CFU/ml were observed for vacuum-packaged and air-packaged cells, respectively. Vacuum packaging followed by storage at 10°C for 4 days caused significant decreases in the resistance of C. sakazakii to heat, acid, and bile salt conditions compared with air packaging. These results suggest that the application of vacuum packaging for powdered infant formula could be useful to minimize the risk of C. sakazakii.

Inactivation of Bacillus cereus spores in infant formula by combination of high pressure and trans-cinnamaldehyde

This study investigated the combined effects of trans-cinnamaldehyde (TC) and high pressure (HP) to inactivate B. cereus spores in reconstituted infant formula. High pressure (600 MPa for 5 min), with or without TC (0.1%), was applied to reconstituted infant formula with B. cereus spores. Samples were stored at 23 and 7 °C for 4 and 6 weeks, respectively. Microbiological and sensory analyses, pH and emulsion stability of each sample were determined. At 7 °C, B. cereus spores in HP and TC treated formula were reduced by 2.4 and 3.1 log, respectively. At 23 °C, the highest inactivation was observed with TC alone and TC combined with HP, by 2.1 log. Overall, HP showed the highest inactivation rate when combined with TC, confirming the synergistic antimicrobial effect of TC and HP. Remarkable deformation and damage in both B. cereus vegetative cells and spores were observed by transmission electron microscopy after the application of HP and TC. Although TC exhibited a cinnamon-like taste, overall sensory attributes were not significantly different than the control samples. These results suggest that TC and HP could be incorporated in infant formula as a natural intervention to replace the synthetic preservatives and/or enhance the microbiological safety and shelf-life.

Formation and structure of insoluble particles in reconstituted model infant formula powders

Phase separation of insoluble particles, so called “white flecks”, is a physical defect in reconstituted milk obtained from spray-dried, fat-containing dairy powders. Compared with bulk powder particles, white flecks have quite different chemical and morphological characteristics. They consist mainly of proteins and fat, forming a dense network. Here, two concurrent formation mechanisms are suggested based on the structures revealed by confocal microscopy imaging. Fused spherical particles with free fat on the surface were the most abundant and likely formed during the manufacturing process. Sharp-edged particles containing shapes typical of lactose crystals formed during storage. Fat globule stability was thus determined to be critical in preventing white fleck formation. Stability was increased with (a) the presence of lecithin in the oil phase; (b) systems with high protein-to-fat ratio and (c) storage in dry conditions since humidity leads to lactose crystallisation and disruption of the fat globules in powders.

Inactivation of Nondesiccated and Desiccated Cronobacter sakazakii in Reconstituted Infant Formula by Combination of Citral and Mild Heat

The objective of this study was to evaluate the combined effect of citral plus mild heat on nondesiccated and desiccated Cronobacter sakazakii in reconstituted infant formula. Various concentrations of citral (0, 0.3, 0.6, and 0.9%) combined with various temperatures (25, 45, 50, and 55°C) were applied to nondesiccated and desiccated cocktails of three C. sakazakii strains (approximately 6.0 log CFU mL-1) in reconstituted infant formula, and the bacterial populations were assayed periodically. The combined treatments had marked antimicrobial effects on C. sakazakii compared with the control. Desiccated cells were more susceptible to citral than were nondesiccated cells in reconstituted infant formula. These findings suggest there is a potential application of citral in combination with mild heat to control C. sakazakii during preparation of reconstituted infant formula.