Covino, Clelia (2023) Neapolitan Pizza: Technological, Nutritional and Health Aspects. [Tesi di dottorato]

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Abstract

Neapolitan pizza is one of the mostly known product of Italian culinary tradition and it is considered as the best food consumed all over the world. Recently, a Production Regulation for Neapolitan pizza has been issued that defines standards for raw materials and technological parameters (EU Reg. 97/2010). Moreover, the importance of the “art” of making Neapolitan pizza has been recognized as “Intangible Cultural Heritage of Humanity” by UNESCO (Jeju, South Corea, 7th December 2017). However, the research community has focused very little attention on Neapolitan pizza, and few data can be found in the scientific literature. This lack of information has generated some misunderstanding on the relationship between frequent consumption of pizza and health, thereby creating unjustified alarm, with negative impact on the economy of pizza business area. Pizza is a medium-energy-density, high-carbohydrate product. It is a good source of protein, minerals, and B vitamins. Starch is the most abundant component of wheat flours, since carbohydrates constitute about 70-80 %, followed by proteins (10-14 %), and lipids, fibre, vitamins and minerals, accounted for a small percentage. Wheat flour is used because the gluten proteins in wheat have unique properties, as the ability to form a viscoelastic dough when wet and kneaded, rather than other grains (Kłosok et al., 2021). Several structural and biochemical changes occur during the pizza making process. The starting raw materials, wheat flour, water, salt and yeast, are mixed in order to be combined to form the dough. The first basic step in dough preparation is to mix water with wheat flour, imparting mechanical energy to form an elastic dough with a strong gluten network (Ooms and Delcour, 2019), with entrapped starch granule inside. This complex matrix has the ability to retain the CO2 generated by the yeast fermentation and allows for the dough volume to expand during leavening. In studying dough formation, there are several limitations to observe physical events on a macroscale, at the supra-molecular level (Stauffer, 1999). Many techniques have been adapted for the study of dough, e.g., X-ray Analysis, Nuclear Magnetic Resonance (NMR), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), but the interpretation of the results is very difficult given the complexity of the matrix. The leavening and baking stages of pizza dough provoke alterations in the structure of the final product, thus affecting the digestibility. Leavening time can contribute to increase digestibility reducing the cohesion between starch and dough protein and increasing the accessibility of starch to α-amylase (Garcia-Hernandez et al., 2022). Indeed, baking allows the water penetration in the starch granules promoting its gelatinization, and this increases the rate of the hydrolysis by facilitating the starch availability to α-amylase action. In addition, at high temperatures, the pizza surface not covered by topping is exposed to the Maillard reaction, which leads to the acrylamide formation, a toxic compound classified as a “probable human carcinogen” (IARC, 1994). Although there is a lack of literature on the level of acrylamide in cooked pizza, targeted interventions for the reduction of this toxic substance are always welcome. All these phenomena must be considered to achieve the desired baked pizza: i) right leavening leading to adequate dough volume and consistency; ii) good digestibility and food quality in the finished product; iii) safe processing for reduction of health concerns. The aim of this PhD thesis was to investigate on Neapolitan pizza: technological, nutritional and health aspects. Specifically, study on dough structure during leavening, starch digestibility and acrylamide content of wood oven baked pizza. The first case study aimed to investigate structural changes over long leavening time (0÷48 h) of pizza dough through physico-chemical analysis, and how rheological parameters may be related to the starch digestibility of the wood oven baked pizza base. Long leavening time of pizza dough showed fewer and weaker interactions of gluten network, attributable to amylolytic and proteolytic activity of yeast. This results in greater extensibility that allows a larger pizza dough diameter by applying less compression force. Moreover, physical and chemical phenomena occurring at long leavening time led to an increase in digestibility index of starch and rapidly available glucose. The second case study aimed to compare the effect of long leavening time (0÷48 h) on pizza dough prepared with selected lactic acid bacteria and yeast, in terms of volumetric index, fermentation and enzymatic hydrolysis products. Significant differences among samples were found for starch digestibility connected with the microstructure (SEM) of dough and respective wood oven baked pizza samples, confirming the more compact the structure, the less rapidly digestible starch (RDS) was found. The third case study aimed to identify the optimal leavening time (0÷24 h) for freezing pizza dough, in order to obtain thawed and leavened dough balls with a similar rheological behaviour compared to the unfrozen control. Freezing, at any leavening time, presented a starch and gluten damage, mainly produced by the formation of ice crystals during storage. The frozen dough before leavening (0 h), showed leavening kinetic and viscoelastic properties similar to the control, but with significant differences in thermal and stress-relaxation properties. The fourth case study aimed to reduce the acrylamide (AA) formation during cooking by treating pizza dough with L-Asparaginase enzyme. Wheat flour was added with commercial enzyme during mixing for the production of pizza dough. Results showed that the use of L-Asparaginase could possibly play a key role in mitigating acrylamide formation in the cooking process of fried and wood oven baked pizza bases, without apparently altering the technological characteristics of the dough. Another strategy to mitigate AA formation was to test selected wheat grains with low asparagine content for making pizza dough. This study clearly showed that mitigation of AA formation in pizza can be achieved by reducing asparagine content in wheat, with a reduction of about 47-68 %, compared to a commercial flour. Further, pizza prepared with wholemeal flours had low starch hydrolysis rate and rapidly available glucose than refined flour. Finally, last case study aimed to develop a calibration and validation models for the fast determination of acrylamide levels in pizza samples through FT-NIR spectroscopy. Overall, good linear correlation was found between the predicted acrylamide levels in solid matrix by NIR method, and the actual acrylamide values measured by UHPLC in extracted pizza samples. This study was useful to examine different aspects related to Neapolitan pizza with a scientific approach, and to fill the gaps in the literature on this topic. Specifically, the structural aspect of the dough during long leavening and the consequences on the digestibility of the pizza were investigated. In addition, AA mitigation strategies were also evaluated to make this much loved and appreciated food safer.

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