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Light effects

Census of the lighting in different local retail markets

A survey of the light sources was carried out in 10 different large-scale retail stores around Milan, noting the typology of the lamps used in the different sections. For each light source the irradiance in the UVA region (Wm-2) and illuminance (lux) were also measured at the level of different foods. The survey showed that 72% of the total light sources was represented by fluorescent lamps and 22% by halogen lamps. The remaining 6% was represented by a combination of both. Among the fluorescent lamps it was possible to distinguish the light sources as a function of the colour temperature and emission spectra of the lamps. The analysis of the principal components (PCA) was used to find a relationship between the lamps and their use in the lighting of different food categories. The first two principal components made it possible to distinguish foods as function of the typology of the lamps. The most widely recorded illuminance values ranged from 1000 to 3000 lux and UVA irradiance values from 0 to 20 mWm-2.

Torri, L., Limbo, S., Piergiovanni, L. 2007.A survey of the food lighting conditions in the large-scale retail stores. Industrie Alimentari. XLVI . 526- 532

Frequency of the fluorescent light source as function of their temperature colorSottotitolo

Light-Induced Changes in an Aqueous Beta-Carotene System Stored under Halogen and Fluorescent Lamps, Affected by Two Oxygen Partial Pressures

The aim of this work was to investigate the reaction kinetics of ?-carotene in an aqueous medium as a function of exposure to commercial lights (halogen and fluorescent sources) and oxygen partial pressures. The evolution of the pigment concentration, the changes in color, and the accumulation of a volatile compound (?-ionone) were monitored during storage. The kinetics of degradation were mathematically modeled to compare the effects of lighting conditions and oxygen partial pressures. Lighting was also a critical variable in the presence of a low oxygen partial pressure (5 kPa), and in these conditions, the ?-carotene degraded completely during storage, even if more slowly than at 20 kPa of O2. The pigment degradation was correlated to illuminance and UVA irradiance values, but the different decay rates of the fluorescent lamps were explained by the differences in the blue region of the energy emission spectra. A halogen lamp gave minor negative effects on ?-carotene degradation.

Limbo, S., Torri, L., Piergiovanni, L. 2007. Light-Induced Changes in an Aqueous ?-Carotene System Stored under Halogen and Fluorescent Lamps, Affected by Two Oxygen Partial Pressures. J. Agric. Food Chem. 55: 5238-5245

Beta-carotene concentration data for cool white and dark storage, modeled with the modified Gompertz equation

Effects of storage temperature, oxygen level and lightness on shelf life of brown parboiled rice.

Brown parboiled rice (BPR) was stored at room temperature (25°C) in dark storage for 25 months and under exposure to light for 130 days to study the light effect on shelf life of this product. The evolution of rancidity was evaluated measuring volatiles by HS-GC method and recording absorbance ratio at 234 nm and 270 nm. In the second part of the work, BPR was stored under different conditions of temperature, oxygen concentrations and package transmittance, which were chosen according to a Central Composite Design in order to assess the simultaneous effects of these variables on the development of rancidity. The results highlighted that the hexanal is really a good index of rancidity in BPR and it can be used in storage experiments to follow the rate of oxidation. The effect of light on BPR degradation is evident and an accelerating factor can be calculated if temperature and oxygen concentration inside the package are kept constant during storage. In fact, the storage of BPR in a flexible package characterized by a transmittance value of 35%, in presence of oxygen at 20.9% and at room temperature, accelerates BPR shelf life of about eight times. The Central Composite Design used in this experimental work has been useful to understand the simultaneous effects of different variables on oxidative status of BPR. This approach showed the important role of oxygen concentration in development of primary oxidation products and the significant effect of temperature in hexanal production. Increasing temperature and oxygen concentration, the effect of package transmittance at the chosen wavelength (330 nm) is less evident. Therefore, these preliminary results are useful to determine the optimal range of variables for an accelerated shelf life test on brown parboiled rice.

Zardi, M., Limbo, S., Aletti, G. 2004. Effects of storage temperature, oxygen level and lightness on shelf life of brown parboiled rice. In: Shelf life degli alimenti confezionati. (Shelf life of packaged foods). Special Issue of Italian Journal of Food Science. Piergiovanni, L., Limbo, S. (Eds) Chiriotti Editori, Pinerolo, Italia

Linear relationship between Ln of hexanal concentration and square root of time.

The protective effect of film metallization against oxidative deterioration and discoloration of sensitive foods

The importance of the optical properties of packaging materials is often underestimated and little attention is generally given to the shelf-life of light sensitive food products. In this paper, the effects of the light barrier of different metallized films in delaying chemical degradative reactions, which occur in dry lasagna made with eggs and spinach, were investigated. The array of films evaluated in the experiment accounted for a large distribution of optical properties. Pouches prepared from the different films were filled with dry lasagna and stored at room temperature for about 4 months under a fluorescent light source. Sensory evaluations, CIE-L*, a*, b* colour measurements and hexanal formation were evaluated during storage. The shelf-life of lasagna packed in metallized films was 2.5 times greater than the same product packed in non-metallized films. A correlation between transmittance values of the packaging films and shelf-life reduction was obtained. Because of the fat and the pigments of lasagna and also its shape (large surface area), lasagna seems to be a good model system when studying the protective performance of packaging materials against degradative reactions that involve oxygen and are very sensitive to light exposure.

L.Piergiovanni, S.Limbo. - The protective effect of film metallization against oxidative deterioration and discoloration of sensitive foods. 2004. Packaging Technology and Science. 155-164.

Red/green colour versus time (average of a* values and SD intervals). A: aluminium foil+thermosealing coating (reference sample); B: two layers of metallized PET; C: metallized OPA; D: metallized OPP; E: metallized OPP; F: metallized CPP; G: un-metallized OPP

Effectiveness of macromolecular non releasing additives in protecting polyethylene films against autoxidation and photoxidation.

This study, carried out with the cooperation of ISMAC (the Institute for Macromolecular Studies-Genova, ISMAC-GE that is part of a CNR institute) is the last part of a more complex work concerning the design and synthesis of Macromolecular Non-Releasing Additives for Commercial Polyolefins. In this study, several novel random copolymers of ethylene and 1-olefinic-units bearing a highly efficient phenolic antioxidant moiety placed at different distances from the double bond were prepared in the presence of metallocene catalysts. These copolymers were melt blended with an antioxidant-free commercial LLDPE in an internal mixer in order to obtain novel materials containing macromolecular non-releasing antioxidants suitable for innovative food packaging applications. Films of the resultant materials were obtained by compression moulding and their thermal and thermo-oxidative stability was tested by TGA analysis both in isothermal and dynamic conditions. In all cases the blends containing the macromolecular antioxidants showed longer induction times before O2 up-take starts and, consequently, higher degradation temperatures with respect to those of the neat matrix and of the blends containing commercial low molecular weight additives. Aging tests were also carried out in order to verify the effectiveness of macromolecular additives in protecting polyolefin matrix when exposed to a light source with a like-sun spectrum. The results demonstrated that the new macromolecular antioxidants constitute a protection against photo-oxidation, comparable to that obtained by using the traditional additives.

Stagnaro, P., Boragno, L., Losio, S., Limbo, S., Menichetti, S., Viglianisi, C., Sacchi, C. 2009. Effects of accelerated light and oxygen exposure on the degradation of polyethylene films containing macromolecular additives. Submitted to Journal of Polymer Science: Part A: Polymer Chemistry