Polymorphic transitions of cocoa butter affected by high hydrostatic pressure and sucrose polyesters

Form V to Form VI transitions of cocoa butter (CB) were investigated by varying the temperature between 28 and 21°C during storage. High hydrostatic pressure (HHP) treatments of CB melt at 60 or 21°C did not affect the rate of Form V to Form VI transitions in CB crystallized in Form V during temperature fluctuations. The HHP treatments with 100, 300, or 600 MPa of CB crystallized in Form V crystals did not alter the rate of Form V to Form VI transitions of CB. The addition of sucrose polyesters to CB melts altered the rate of Form V to Form VI transitions of CB and was dependent on the FA chain lengths and hydrophilelipophile balance (HLB) values of the SPE. The addition of most SPE to CB melts promoted the polymorphic transitions; however, sucrose polyester S-170 containing FA of chain length similar to CB with small HLB values inhibited Form V to Form VI transitions of CB for 10 temperature fluctuation cycles. Therefore, HHP treatments can be applied to foods containing high fat with little effect on the polymorphic transitions, and selected SPE may be used to retard adverse polymorphic transitions.     

Production of lipid from N‐acetylglucosamine by Cryptococcus curvatus

N‐Acetylglucosamine (GlcNAc), the monomeric constituent of chitin, is rarely used as a carbon source for fermentation technology. In this study, we demonstrate that the oleaginous yeast Cryptococcus curvatus ATCC 20509 can produce intracellular lipid during the cultivation process and total lipid content can reach 54% on a GlcNAc‐based medium. Culture of C. curvatus under various conditions indicated that lipid accumulation also occurred at a relatively broad range of temperatures as well as relatively high initial GlcNAc concentrations. Fatty acid analysis indicated that the product was rich in palmitic acid, stearic acid, and oleic acid, closely resembling the composition of palm oil. More importantly, the lipid sample produced at 22 °C had a total saturated fatty acid content of 54.2 wt%, suggesting that it may be explored as cocoa‐butter equivalent. Our data suggested that GlcNAc could be used as a feedstock for industrial biotechnology and that C. curvatus ATCC 20509 is a strain capable of accumulating high intracellular lipid using this nitrogen‐rich renewable material. Practical applications: Microbial lipid is a versatile material, especially for biodiesel production. Stable and abundant renewable raw substrates remain to be explored for large‐scale production of microbial lipid. The present work reports lipid production using N‐acetylglucosamine (GlcNAc) by the oleaginous yeast Cryptococcus curvatus ATCC 20509 to yield up to 54% intracellular lipid content. More significantly, the lipid sample produced at 22 °C had a total saturated fatty acid content of 54.2 wt%, suggesting that it may be explored as cocoa‐butter equivalent. Our technology provides the opportunity to effectively convert GlcNAc, available from one of the most abundant renewable materials chitin, into lipid. This procedure should prove valuable in terms of renewable energy production as well as environmental pollution control.     

Influencing cocoa flavour using Pichia kluyveri and Kluyveromyces marxianus in a defined mixed starter culture for cocoa fermentation

The potential impact of aromatic and pectinolytic yeasts on cocoa flavour was investigated using two defined mixed starter cultures encompassing strains of Pichia kluyveri and Kluyveromyces marxianus for inoculating cocoa beans in small scale tray fermentations. Samples for microbial and metabolite analysis were collected at 12–24 hour intervals during 120 h of fermentation. Yeast isolates were grouped by (GTG)₅-based rep-PCR fingerprinting and identified by sequencing of the D1/D2 region of the 26S rRNA gene and the actin gene. Pulsed Field Gel Electrophoresis (PFGE) was conducted on isolates belonging to the species P. kluyveri and K. marxianus to verify strain level identity with the inoculated strains. Furthermore, Denaturing Gradient Gel Electrophoresis (DGGE) was performed to follow yeast and bacterial dynamics over time including the presence of the bacterial inoculum consisting of Lactobacillus fermentum and Acetobacter pasteurianus. Yeast cell counts peaked after 12 h of fermentation with the predominant species being identified as Hanseniaspora opuntiae and Hanseniaspora thailandica. P. kluyveri and K. marxianus were found to compose 9.3% and 13.5% of the yeast population, respectively, after 12 h of fermentation whilst PFGE showed that ~ 88% of all P. kluyveri isolates and 100% of all K. marxianus isolates were identical to the inoculated strains. Despite never being the dominant yeast species at any stage of fermentation, the un-conched chocolates produced from the two inoculated fermentations were judged by sensory analysis to differ in flavour profile compared to the spontaneously fermented control. This could indicate that yeasts have a greater impact on the sensory qualities of cocoa than previously assumed.     

The content of protein and non-protein (free and protein-bound) tryptophan in Theobroma cacao beans

The contents of protein and non-protein (free and protein-bound) tryptophan and of proteins in cocoa beans of various origin were determined. Protein concentrations varied from 11.8 g/100 g in beans from the Dominican Republic to 15.7 g/100 g in roasted beans from the Ivory Coast. The highest protein tryptophan content was found in cocoa beans from Ecuador. Madagascar beans had the highest value of free tryptophan and Echeandia the lowest (17.26 and 6.39 mg/100 g, respectively). Tryptophan was bound to water-soluble proteins as well as to proteins soluble in buffer solution (pH 8.9) and in 70% ethanol. In particular, Dominican Republic cocoa contained the highest amount of tryptophan bound to water-soluble proteins. Very little tryptophan was linked to proteins soluble in alkaline or ethanol solutions, and values ranged from 0.96 to 3.04 and from 0.24 to 1.21 mg/100 g of dry defatted cocoa sample, respectively.     

Quantification of cocoa butter equivalents in mixtures with cocoa butter by chromatographic methods and multivariate data evaluation

Received: 25 August 1999     

Is the taste of British milk chocolate different?

The flavour of a piece of chocolate can be affected by the type and amount of ingredients present, as well as by the processing techniques used. This article reviews the factors that alter the taste of milk chocolate and considers whether a unique British flavour exists. Chocolate varieties with a wide range of flavours are currently being sold throughout the world and most are available within the UK. It is concluded that the existence of a unique British milk chocolate flavour may be due to the widespread use of chocolate crumb as an ingredient, which introduces a cooked taste into the final product.     

Influence of Brazilian Geographic Region and Organic Agriculture on the Composition and Crystallization Properties of Cocoa Butter

Cocoa butter (CB) is the most important ingredient in chocolate and represents the biggest share in the continuous phase of this product. The accurate composition of CB depends, among other factors, on the genetic characteristics of the cocoa tree, its agricultural handling and the farming region's climate. The influences of the cocoa‐producing region in Brazil and the agricultural cultivation method on the composition and crystallization properties of CB are presented in this article. Raw CB was extracted from fruits cultivated in six main Brazilian states using two agricultural methods, organic and conventional. The samples were evaluated according to fatty acids, triacylglycerol composition, solid fat content, consistency, melting behavior and isothermal crystallization. The wide range of cocoa‐producing regions in Brazil causes the distinct characteristics of the chemical composition and crystallization behavior of the CB, attributes that affect the quality of products using this raw material. Differences in consistency, hardness and crystallization parameters, among others, were observed. The results showed the great potential of using Brazilian CB with similar features to those of African and Asian origin, considered more appropriate for use in chocolates. However, no clear tendency concerning the agricultural method was found.     

Determination of theobromine,theophylline and caffeine in cocoa samples by a high-performance liquid chromatographic method with on-line sample cleanup in a switching-column system

A simple reversed-phase high-performance liquid chromatographic method was developed for the determination of theobromine, theophylline and caffeine in cocoa samples. In the sample cleanup step, the procedure involves an on-line solid-phase extraction of analytes from cocoa samples into a home-made dry-packed pre-column with ODS-C₁₈ using a column-switching system. The separation was performed on a C₁₈ Nova-Pak column (150 mm × 3.9 mm, 4 μm) using a mobile phase consisting of a solution of 20% of methanol in water under isocratic conditions, at a flow-rate of 1.4 ml/min. The validation method revealed quantitative recoveries (>95.0%) with a coefficients of variation <3.2% and it also provided a good precision for data validation. The overlap of sample cleanup, analysis and recondition of the precolumn increases the sample throughput to 8 samples/h. Furthermore, the proposed method was successfully applied to analysis of cocoa samples “Trinitario”, “Forastero” and “Criollo” grown in different seasons of the year and fermented for 3 and 7 days, respectively. The results showed a slight reduction in the theobromine and caffeine content according to the fermentation times. In the same way, the theobromine/caffeine ratio was assessed, with the purpose of establishing a correlation with the genotype of the studied samples.     

Effect of polyphenol and pH on cocoa Maillard-related flavour precursors in a lipidic model system

Polyphenol and pH influence the flavour quality of cocoa beans during roasting. Amino acids and reducing sugars are flavour precursors in cocoa beans, which develop into cocoa-specific aroma through Maillard reactions during roasting. A central composite design was applied to determine the combined effect of polyphenol and pH on the flavour precursors during cocoa roasting at 120 °C for 45 min using a lipidic model system. Polyphenol was added at 40, 80 and 120 g kg⁻¹ and pH was adjusted to 4.5, 6 and 7.5. The response surface methodology revealed that a lower concentration of amino acids and reducing sugars was obtained at higher polyphenol concentration (120 g kg⁻¹) and lower pH value (4.5). Based on the constraints set, the best polyphenol concentration of 43–58 g kg⁻¹ and pH of 7.0–7.5 was found to be optimum for the formation of flavour precursors in this lipidic model study.