Research Question
Every step of food processing alters the quality of the original raw material. Breakfast cereals, such as roasted flakes and extruded or puffed products, fall under ultra-processed foods. In contrast, organic and Demeter foods are expected to remain as natural as possible. According to the EU regulation on organic farming, only processing methods that preserve the ecological characteristics and qualities of the products are permitted (EU Regulation 2018/848). This raises the question of whether the quality of organic breakfast cereals is preserved during production.
The study examined four different types of grains (spelt, buckwheat, rice, quinoa) and breakfast cereals made from them, processed using different methods. Various quality aspects of the products were analyzed:
- Concentrations of heat-sensitive chemical components that are related to human health.
- Structural aspects of the foods, measured using a holistic method (fluorescence excitation spectroscopy) to assess sensitive quality aspects related to processing intensity.
- Food-induced emotional experiences (Wirksensorik®), capturing the physical and emotional responses after consuming the food.
Methodology
The study was conducted in Germany through collaboration between the KWALIS Research Institute, Forschungsring e.V., and Wirksensorik GmbH.
Spelt (Triticum spelta), buckwheat (Fagopyrum esculentum), rice (Oryza sativa), and quinoa (Chenopodium quinoa) were sourced from certified organic farms and examined in raw form and processed using four methods: flaking of steamed grains (F), flaking and roasting of cooked grains (FR), extrusion of dough (E), and puffing of grains (P). Quinoa was not processed using methods (FR) or (P).1
The content of the grains was analyzed for concentrations of vitamin B1 (thiamine), vitamin B9 (folate), lysine, and acrylamide (a harmful substance). Vitamins B1 and B9, as well as the amino acid lysine, are heat-sensitive and serve as markers for heat-related degradation, while acrylamide is a parameter for the formation of harmful substances during heating.
The food structure was assessed using fluorescence excitation spectroscopy, a method developed by the KWALIS Institute and described by Stolz et al. (2019)2. This method measured the delayed fluorescence of each sample by recording photon emissions after visible light excitation in seven different wavelength ranges. A total of 108 parameters were evaluated, including short- and long-term emissions for each color of excitation.
Food-induced emotions were measured using the EmpathicFoodTest, developed as Wirksensorik by Geier et al.3. This test involved 12 polar questions, examining participants' physical and emotional states (e.g., warm vs. cold, awake vs. tired, nervous vs. relaxed) and the duration of these states. Only processed products from spelt and buckwheat were tested.
Results
The results showed that all samples experienced processing-related losses of vitamins B1 and B9, as well as lysine. Flaking of steamed grains (F) caused only minor losses of vitamin B1, with the content after processing remaining at 81% ± 18%. In contrast, roasted flakes (FR), extruded dough (E), and puffed grains (P) exhibited the highest vitamin losses. Puffed grains had the lowest vitamin B1 content, retaining only 10% ± 7% compared to raw grains. Lysin levels were also significantly reduced in puffed samples, especially in rice and spelt, with a retention of only 60% ± 9%.
No acrylamide was detected in any of the flaked (F) samples (<10 ± 0 µg kg-1). However, roasted flakes (FR) and puffed grains (P) contained elevated acrylamide levels across all grain types, especially spelt (>200 µg kg-1). Acrylamide was detected in extrudates (E) only in spelt, likely due to its higher sugar content (4-6 g/100 g), as sugars, along with amino acids, are precursors for acrylamide formation under heat.
The delayed fluorescence analysis indicated that the samples responded differently to processing. The intensity of the delayed photon emission is known to correlate with product aging and the agricultural production of the raw materials. The excitation spectrum reflects the physiological state of the products: broad spectra with relatively high emissions after yellow and red excitation are characteristic of leaf-like samples and can indicate growth processes, while narrow spectra dominated by blue and white emissions are observed in grains during dormancy—indicating that growth has led to differentiation. Extremely narrow spectra are present in non-organic materials, such as crystals, stones, or metal. In this study, raw grains exhibited broad relative spectra, while processed samples showed narrower spectra. These emission pattern shifts indicated a significant loss of grain-specific quality in highly processed samples (roasted flakes and extrudates). Overall emission after yellow and green excitation also showed similar results: highly processed products had high overall emissions, while raw grains exhibited low overall emissions. Flakes of steamed grains (F) emitted at an intermediate level. This method of investigation demonstrated a decline in original quality, depending on heat exposure and processing intensity.
The EmpathicFoodTest confirmed that the type of processing influenced food-induced emotions. For example, steamed grain flakes (F) were associated with more positive emotions, more pronounced in spelt than in buckwheat. The evaluation of food-induced emotions aligned with the results of delayed fluorescence but differed from the analytical parameters. For instance, extrudates (E) from both spelt and buckwheat were rated the lowest, although the chemical-analytical parameters showed less harmful effects of extrusion compared to puffing or roasting.
The findings show that quality losses occur with every processing method tested. Flaking of steamed grains (F) was the method that best preserved the original quality of the grains, making it a gentle and quality-friendly processing method. The results also suggest that certain quality aspects are not captured by chemical-analytical parameters but are reflected in delayed fluorescence and food-induced emotions.
Discussion
Some foods, such as raw grains, are initially not very digestible, or not at all. Only through processing, such as germination or heat application, do they become digestible for humans. Thus, food processing can be beneficial and considered an enhancement. It is successful when digestibility and aroma are improved, and the nutrients are largely preserved. As this study shows, material analysis can assess health impacts, such as acrylamide formation, which should be avoided due to its carcinogenic effects and is therefore considered a quality detractor. However, the study also highlights that material analysis alone is insufficient for a comprehensive assessment of quality. The results support the notion that there are quality aspects not measurable by purely quantitative analytical methods, but which are reflected in delayed fluorescence and food-induced emotions. Such methods allow for a holistic assessment of quality.
Source: J Wohlers, P Stolz, U Geier (2024): "Intensive processing reduces quality of grains: a triangulation of three assessment methods," Biological Agriculture & Horticulture, DOI: 10.1080/01448765.2023.2295868
1 The process for producing flakes (F) involved steaming the whole grain (approx. 70°C), followed by rolling (flaking) and drying at low temperatures. Roasted flakes (FR) were made from grains that were cooked before flaking, then dried and roasted at high temperatures. For extruded products (E), a dough made from ground grain was subjected to heat and pressure and then pressed through a die. For puffing (P), whole grains were moistened with steam and then subjected to high temperatures and pressure. A rapid pressure drop caused the grains to expand or puff. The heat exposure was lowest during the processing of (F) and highest during (P).
2 Stolz P, Wohlers J, Mende G. (2019): Measuring delayed luminescence by FES to evaluate special quality aspects of food samples – an overview. Open Agric. 4(1):410-417. doi: 10.1515/opag-2019-0039.
3 Geier U, Buessing A, Kruse P, Greiner R, Buchecker K (2016): Development and Application of a Test for Food-Induced Emotions. PLoS ONE 11(11): e0165991. doi:10.1371/journal.pone.0165991
