Pierre A. Picouet

Feasibility of near-infrared spectroscopy to predict aw and moisture and NaCl contents of fermented pork sausages

The feasibility of near-infrared spectroscopy (NIR) for predicting parameters related to the drying process of fermented sausages (water activity (a(w)), moisture, and NaCl contents) was assessed. A FT-NIR spectrometer and two spectra acquisition setups with contact and remote probes were tested. NIR calibration models were developed using 207 samples scanned between 12,000 and 4000cm(-1) (833-2500nm) in reflectance mode. Partial least squares (PLS) regression was used to process spectra and develop calibrations. Predictive models for moisture, a(w) and NaCl yielded 0.997, 0.988 and 0.974 determination coefficients in prediction (R(p)(2)) respectively with the on-contact probe method, and 0.998, 0.985 and 0.974 respectively with the remote measurement head method. Furthermore 0.675, 0.006 and 0.117 root mean square errors of prediction (RMSEP) were achieved with the contact probe method, and 0.622, 0.007 and 0.116 with the remote measurement head method. The results confirmed that NIR spectroscopy is an useful technique for predicting moisture and NaCl and suggest it could also be useful to predict a(w) on the surface of fermented sausages. Both setups are appropriate for further on-line applications for monitoring drying processes in a non-destructive way with non-significant differences in the predictive accuracy.

Influence of PA6 nanocomposite films on the stability of vacuum-aged beef loins during storage in modified atmospheres

A masterbatch of polyamide 6 (PA6) containing dispersed nanoclays, was used to fabricate a novel multilayer film for vacuum packed meat. Performance of the nanocomposite was compared to a control PA6 multilayer and a high barrier commercial film. Addition of nanoclays improved oxygen barrier properties, UV-blocking capability and stiffness. Beef loins were vacuum-aged using the three films for 0 7, 14 and 21 days at 2°C. After each ageing time, beef steaks were packaged in commercial trays and high oxygen atmosphere and stored at 4°C for 9 days. Beef quality parameters and gas content were studied during display time in MAP (1, 3, 6 and 9 d). Beef quality parameters were not influenced by the packaging materials used during ageing and the performance of nanocomposites was comparable to high barrier films. Ageing had a positive impact on the stabilization of redness up to day 6 in MAP. Thereafter, oxymyoglobin content and oxidation levels were negatively influenced by ageing.

Effect of marination and microwave heating on the quality of Semimembranosus and Semitendinosus muscles from Friesian mature cows.

Semimembranosus (SM) and Semitendinosus (ST) muscles from 8 mature cows were used to evaluate the effect of marination, power of microwave heating, and internal temperature of cooking on the quality of calibrated beef roasts. Four treatments, using combinations of power (182W and 654W) and temperature (60 and 80°C) were applied to marinated (10% added brine: salt, sodium lactate, lactose, and ascorbate) and control roasts from SM (15×5×3cm) and ST (10×4×3cm) muscles in a 2×2×2 factorial arrangement. Microwave cooking was heterogeneous resulting in a gradient of temperatures within the roasts. Either high or low microwave power were appropriate for cooking ST roasts, but SM roasts cooked at 654W showed higher cooking losses, and lighter and less red cooked color than 182W. Cooking to 80°C increased cooking and color losses in both muscles and decreased tenderness of SM roasts compared with 60°C. Marination can be used successfully to enhance beef tenderness of ST and SM muscles cooked in microwave.

Stabilization of Red Fruit-Based Smoothies by High Pressure Processing. Part A. Effects on microbial growth, enzyme activity, antioxidant capacity and physical stability.

BACKGROUND Non-thermal pasteurization by high-pressure processing (HPP) is increasingly replacing thermal processing (TP) to maintain the properties of fresh fruit products. However, most of the research on HPP-fruit products only partially addresses fruit-pressure interaction, which limits its practical interest. The objective of this study was to assess the use of a mild HPP treatment to stabilize red fruit-based smoothies (microbial, enzymatic, oxidative and physical stability). RESULTS HPP (350 MPa/10 °C/5 min) was slightly less effective than TP (85 °C/7 min) in inactivating microbes (mesophilic and psychrophilic bacteria, coliforms, yeasts and moulds) in smoothies kept at 4 °C for up to 28 days. The main limitation of using HPP was its low efficacy in inactivating oxidative (polyphenol oxidase and peroxidase) and hydrolytic (pectin methyl esterase) enzymes. Data on antioxidant status, colour parameters, browning index, transmittance, turbidity and viscosity confirmed that the HPP-smoothies have a greater tendency towards oxidation and clarification, which might lead to undesirable sensory and nutritional changes (see Part B). CONCLUSION The microbial quality of smoothies was adequately controlled by mild HPP treatment without affecting their physical-chemical characteristics; however, oxidative and hydrolytic enzymes are highly pressure-resistant, which suggests that additional strategies should be used to stabilize smoothies.

Relevance of nanocomposite packaging on the stability of vacuum-packed dry cured ham.

In this study effects of a novel high barrier multilayer polyamide film containing dispersed nanoclays (PAN) on the stability of vacuum packed dry-cured ham were investigated during 90days refrigerated storage in comparison with non-modified multilayer polyamide (PA) and a commercial high barrier film. Characteristic bands of the mineral in FT-IR spectra confirmed the presence of nanoclays in PAN, enhancing oxygen transmission barrier properties and UV protection. Packaging in PAN films did not originate significant changes on colour or lipid oxidation during prolonged storage of vacuum-packed dry-cured ham. Larger oxygen transmission rates in PA films caused changes in CIE b* during refrigerated storage. Ham quality was not affected by light exposition during 90days and only curing had a significant benefit on colour and TBARS, being cured samples more stable during storage in all the packages used. Packaging of dry-cured ham in PAN was equivalent to commercial high barrier films.