## 4 Use of Spectroscopic Techniques for Monitoring Changes in Muscle Foods during Processing
### Meat and Poultry Products
#### 4.2.1 Thermal Treatments
Measurements were collected in a similar spectral range as before (761-1081 nm) on samples presenting diverse temperatures (between 60 and 90 \({}^{\circ}\)C). The proposed approach was definitely successful; in fact, it allowed predicting core temperatures with an accuracy of \(\pm\)1 \({}^{\circ}\)C.  
Fluorescence Spectroscopy: Front-face fluorescence (in EEM mode) has been widely used to examine the effect of heating procedures on meat. [PERSON] has conducted, together with different collaborators, several fluorescence-based studies on thermal effects on meat. In the most recent one [168], EEM spectra were collected on beef longissimus dorsi muscle cooked at 66, 90, or 237 \({}^{\circ}\)C for 1, 2, 5, 7, or 10 min. PCA and parallel factors (PARAFAC) analysis were run on data. In agreement with precedent work [212], explorative analysis allowed discriminating samples according to the cooking time. The inspection of PARAFAC components indicates that the most relevant contributions to the model are given by tryptophan (excitation: 297 nm; emission: 327 nm) and to peaks (excitation: 468 nm; emission: 538 nm) tentatively associated by the authors (in agreement with the literature) to  
Figure 3: Hyperspectral images of chicken breasts (**a**), and water dispersion map of chicken breasts (**b**). Adapted from [208]. hydroxymethylfurfural (HMF). Other relevant EEM bands are between 325-400 and 395-470 nm, probably relatable to oxidation of lipids. In another work, [PERSON] used EEM (coupled with N-PLS) to investigate a family of mutagens and carcinogens compounds, the heterocyclic amines, developed by grilled meat [213]. Similarly, fluorescence was used by [PERSON] and others to determine toxic compounds (by-products of Maillard reactions) in cooked meat [214] and by [PERSON] and coauthors to investigate peptide oxidation (due to thermal treatments) [215]. Moreover, this technique has been used to study the impact of home cooking conditions by investigating fluorescence compounds produced during Maillard reactions. An example in this regard is the work [PERSON] and collaborators [216], conducted on beef burgers. In this study the authors observed that, when the internal part of meat samples reaches temperatures lower than 90 \({}^{\circ}\)C (by grilling or frying), there was an increase in furosine; on the other hand, at higher temperatures (between 90 and 100 \({}^{\circ}\)C), the amount of this compound decreases. When burgers were oven cooked at 300 \({}^{\circ}\)C, an increase in carboxymethyllysine content was detected. Moreover, the authors noticed that, regardless of the cooking conditions, the acrylamide content was parsimonious in all cases. The results showed that boiling was the cooking procedure that resulted in the lowest amount of Maillard by-products. In a similar context, fluorescence was also used to investigate the formation of Schiff base structures (as in seafood) during processing of chicken patties in a study proposed by [PERSON] and collaborators [217]. In this work, the extent of proteins oxidation caused by diverse cooking procedures (grilling, roasting, boiling, and microwaving) was investigated. The authors concluded that, regardless of the cooking treatment, oxidation occurs, and chilling enlarges the oxidation effects, making chicken fleshes harder. Nuclear Magnetic Resonance (NMR): NMR has been exploited for inspecting the effects of thermal treatments on meat products, in particular for studying water distribution in processed fleshes. One example is the work conducted by [PERSON] and collaborators, who used this technique to investigate the water dispersion in beef braised at different temperatures (from 45 to 95 \({}^{\circ}\)C using 10 \({}^{\circ}\)C steps) for diverse period of time (from 30 to 120 min by 30 min steps) [218]. The analysis revealed that \(T_{2}\) was correlated with temperature.