Detection and identification of xerophilic fungi in Belgian chocolate confectionery factories

Effect of High Pressure on the Properties of Chocolate Fillings during Long-Term Storage

The aim of this study was to evaluate the impact of high-pressure processing (HPP) on the long-term storage of chocolate fillings at room temperature, compared with conventional storage at lower temperatures. Dark chocolate fillings were treated at different pressure levels, holding times and stored at 20 °C for 12 months. Unprocessed batches were stored at 4 °C and at −12 °C. Moisture, water activity (aw), pH, colour, G′_1Hz and indigenous microflora were measured at 2, 4, 6, 8, 10 and 12 months of storage. Results showed that 600 MPa/20 min processing was the most effective controlling mesophilic group, presenting 3.8 log cfu/g after 12 months of storage, and inactivating moulds and yeasts after HPP treatment. Colour was affected by storage, including a reduction in the L* parameter in all conditions to final values between 37.8 and 39.3, while the a* parameter increased during storage time at −12 °C and 4 °C to final values of around 12, and parameter b* decreased at storage temperature 20 °C to 5.3. Storage time affected the rheological behaviour of HPP-treated samples, increasing G′_1Hz from the 2nd to 12th month of storage time to the final values between 1603 kPa and 2139 kPa. Moisture, aw and pH were not affected by HPP treatment nor storage time.

Extended Enrichment Procedures Can Be Used To Define False-Negative Probabilities for Cultural Gold Standard Methods for Salmonella Detection, Facilitating Comparisons between Gold Standard and Alternative Methods

ABSTRACT

Evaluation of alternative detection methods for foodborne pathogens typically involves comparisons against a "gold standard" culture method, which may produce false-negative (FN) results, particularly under worst-case scenarios such as low contamination levels, difficult-to-detect strains, and challenging food matrices (e.g., matrices with a water activity of <0.6). We used extended enrichment times (up to 72 h for both primary and secondary enrichments) to evaluate a gold standard method for Salmonella detection (the U.S. Food and Drug Administration Bacteriological Analytical Manual [BAM] method) in two low-water-activity foods (dry pet food and chocolate) inoculated at low contamination levels (most probable number ca. 1/25 g) with five Salmonella strains. Strains were selected to include those with a poor ability to grow in enrichment media. Among the 100 pet food and 100 chocolate samples tested, 53 and 50, respectively, were positive with the standard BAM method, and 57 and 59, respectively, were positive with the extended BAM method. Thus, the FN probabilities for the standard BAM method were 7% for pet food and 15% for chocolate. An alternative enzyme immunoassay method for detection of Salmonella in chocolate produced FN probabilities of 6 and 20% when compared against the standard and extended BAM methods, respectively. Detection of Salmonella Mississippi was significantly reduced with the alternative method (P = 0.023) compared with the extended BAM method. We calculated a composite reference standard to further define FN probabilities based on variable results from multiple assays (the standard BAM, extended BAM, and alternative methods). Based on this standard, the enzyme immunoassay for Salmonella detection in chocolate had a 28% FN probability and the standard and extended BAM methods had 23 and 9% FN probabilities, respectively. These results provide a framework for how inclusion of extended enrichment times can facilitate evaluation of alternative detection methods.

HIGHLIGHTS

Thermal Resistance of Xerophilic Fungi in Low-Water-Activity (0.70 to 0.80) Confectionery Model Foods

Consumers are increasingly searching for preservative-free and "natural" food options. Confectionery products with low water activity (a_w) are typically considered resistant to contamination with filamentous fungi; however, several xerophilic fungi can cause considerable economic losses due to spoilage. Very few studies have been published addressing filamentous fungi that are tolerant to low a_w in food products containing all nutrients essential for filamentous fungi growth, including sugars, carbohydrates, proteins, and fats, but not preservatives. The objective of this study was to evaluate the effect of a_w on the thermal tolerance and survival of one strain of Aspergillus pseudoglaucus and two strains of Aspergillus fischeri. The decimal reduction time ( D-value) and the temperature needed for a 1-log change in D-value ( z-value) in a low-acid (pH 6) confectionary model comprising evaporated milk and fructose adjusted to a_w of 0.70, 0.75, and 0.80 were determined by creating thermal death time curves. Experiments were performed in triplicate. A. fischeri had higher thermal tolerance than did A. pseudoglaucus. An interaction between a_w and temperature was found; however, it was not linear with respect to a_w. A. fischeri had the highest thermal tolerance for 0.75 a_w at 90°C ( D-values of 11.5 to 34.8 min) compared with 0.70 and 0.80 a_w, for 0.80 a_w or 0.75 a_w depending on the strain at 92°C (4.3 to 17.1 min), and for 0.75 a_w at 94°C (2.4 to 7.7 min). A. pseudoglaucus had the highest thermal tolerance for 0.70 a_w at 78°C ( D-value of 4.9 min), 80°C (1.7 min), and 82°C (0.8 min). The data from this study will be useful for determining parameters for thermal processing of low-a_w confectionary products to control the growth of xerophilic fungi.

State-of-the-Art Chocolate Manufacture: A Review

The aroma, taste, shine, snap, smoothness, "melt-in-your-mouth" sensation, and texture are all qualities that define chocolate, and all depend on how the cocoa and the chocolate itself are processed. Postharvest handling of the cocoa (fermentation, drying, cleaning, storage, and transport) and its transformation into chocolate (roasting, grinding, conching, tempering, molding, and the addition of core and other ingredients), as well as the packaging, storage, transport, and refrigeration of the finished product all have an important influence on the characteristics of chocolate. The aim of this review was to identify and study the key factors, including microbiological aspects that affect the quality of chocolate, from harvesting the beans right up to the manufacture of the finished products.