Chocolate Tempering: A Perspective

Abstract

Tempering is a critical step in chocolate production, ensuring desirable properties such as gloss, snap, and bloom resistance. Traditionally, tempering has been understood through the lens of cocoa butter polymorphism, with a predominant focus on achieving Form V crystals, due to their sharp melting profile and associated macroscopic physical properties. However, this Perspective challenges the notion that Form V alone guarantees high-quality, bloom-resistant chocolate. Recent research suggests that polymorphism is only one aspect of chocolate quality. Multiscale structural analyses-including small-angle X-ray scattering (SAXS), ultrasmall-angle X-ray scattering (USAXS), small-angle neutron scattering (SANS), and microcomputed tomography (μCT)-reveal that nanostructural to microstructural properties are key indicators of bloom susceptibility and can vary significantly, despite identical polymorphic phases. This Perspective proposes that tempering should be viewed as a hierarchical crystallization process, where nucleation rate, structural homogeneity, and microstructural organization play critical roles. A broader approach to tempering assessment-integrating microstructural probes alongside traditional solid-state characterization-may provide deeper insights into chocolate's mechanical stability and long-term bloom resistance. As supply chain fluctuations increasingly impact cocoa butter composition, this multiscale perspective could help manufacturers mitigate quality inconsistencies and adapt to cost-driven formulation changes that may otherwise compromise bloom resistance in tempered chocolate.

Figure 1

Molecular configuration that can be adopted by triacylglycerols, and their typical stacking configurations, 2L and 3L.

Figure 2

Chocolate tempering schematic. Rapid cooling leads to the formation of unstable polymorphs that undergo rapid polymorphic transitions, leading to Type 1 bloom. Untempered and under-tempered chocolate result in Type 2-A and Type 2-B bloom, respectively. Overtempered chocolate, created due to improper storage and exposure to temperature cycles of high temperature, produces Type 3 bloom and typically occurs over extended periods of time.

Figure 3

Representative (A–C) wide-angle X-ray scattering patterns and (D–F) differential scanning calorimetry curves of Forms IV, V, and VI polymorphs in cocoa butter.

Figure 4

(A) Typical three-point bending setup and (B) typical corresponding force vs displacement profile.

Figure 5

Visual representations of the W–H plot and the parameters one can derive from it, where the slope ε is equal to the lattice strain and y-intercept is used to solve for the crystallite size (D_p).

Figure 6

(A–C) Selected 2D SR-μCT slices comparing the macro- and microstructures of DMPC-tempered chocolate. Regions of precrack formation are highlighted in (D). (E) shows a low-magnification volume rendering of developed cracks (green), with cocoa solids and sugar in red and cocoa butter rendered transparent. In (F), a higher magnification of a similar region shows cocoa solids and sugar in yellow and red, and cocoa butter in green. [Schematic partially adapted from Chen et al. and Stobbs et al. Modified from the original by combining and adding panels.]

Figure 7

Molecular structure of DMPC and POS with color-coded functional groups corresponding to the displayed FTIR spectra of (A) choline moieties, asymmetric C–N stretch (ν_asC–N⁺(CH₃)₃) and symmetric stretching of –N–(CH₃)₃ and asymmetric C–H bending of polar headgroup in DMPC (red); (B) phosphate moieties of asymmetric (ν_as(PO₂^–)), symmetric (ν_s(PO₂^–)) in DMPC (yellow); (C) ester moieties of C=O in both DMPC and POS (green); and (D) alkyl chain moieties of symmetric and asymmetric ν_s(CH₃), ν_as(CH₃), ν_s(CH₂), and ν_as(CH₂) in DMPC and POS (blue). [IR spectra in the schematic were partially adapted from Stobbs et al. Modified from the original by isolating the DMPC spectrum and adding color-coded regions corresponding to the functional groups of the DMPC/POS molecule.]

Figure 8

Environmental scanning electron microscopy of (A) ground DMPE and (B) DMPC. [Adapted from Stobbs et al. (2025).]

Figure 9

Images of chocolate produced and stored for 1 year at 20 °C to observe bloom formation: (A) untempered, (B) DMPC-tempered, (C) DMPE-tempered, and (D) tempered. All chocolate other than the DMPE-tempered formed varying levels of bloom during the storage period.

Figure 10

Small-angle X-ray scattering pattern of DMPC-tempered chocolate shown to be primarily in Form V with small amount of Form IV CB. [Modified image from Stobbs et al. by replotting data with only the DMPC SAXS pattern.]

Figure 11

(A) XRD patterns of tempered and untempered dark chocolate showing that the cocoa butter crystals in both chocolates are in Form V, regardless of the tempering. Peaks 1–7 are the shorting spacings of the Form V polymorph at 5.4, 5.21, 4.57, 3.97, 3.85, 3.74, and 3.65 Å. B) Elastic bending modulus of tempered and untempered chocolate. A higher modulus is correlated with better snap (brittle fracture).

Figure 12

Small-angle neutron scattering (SANS) profiles of tempered and untempered 100% (A) and 70% (B) dark chocolates. Due to background scattering contributions from sugar and cocoa solids, the decay exponents are similar and no significant differences can be observed.

Figure 13

Small-angle neutron scattering (SANS) profiles of two tempered CB (pink and tan) and untempered CB (green). All samples display the Form V diffraction peaks at 64.0 Å and 32.1 Å, while only the untempered sample displays a diffraction peak of Form IV at 45.5 Å, and an additional peak at ∼190 nm, possible from CNP. Slope exponents are displayed for each sample.

Figure 14

(A) Ultra-small-angle X-ray scattering (USAXS) profiles of tempered and untempered CB showing two distinct regions which can be analyzed. (B) Lower Q values of selected samples, highlighting a structural feature with periodic order at ∼690 nm.

Figure 15

Visual schematic of the multiscale fat crystallization process observed by Mid-IR, WAXS, SAXS/WAXS, USAXS, and μCT.