Material Contact and Environmental Effects on Vitamin A Fortified Vegetable Frying Oil

The impact of environmental parameters and time, on fortified vegetable oil, using typical commercial grade linear low density polyethylene (LLDPE) packaging during typical shelf-life conditions, were studied over long-term (12 months) to evaluate impact of temperature and illuminance (light: 100 to 150 lux and darkness <1 lux) on refined bleached deodorized palm olein (RBDPOL), fortified with vitamin A, without antioxidant. Results showed degradation of fortified RBDPOL with 70 ppm vitamin A was approximately 19% at 18-22C in Light, 18% at 18-22C in Darkness, 38% at 32-33C in light and 24% 32-33C in darkness. A similar trend was observed at 45 ppm vitamin A. Irrespective of the contact packaging material, a prolonged exposure at elevated temperature significantly impacts vitamin A depletion.


I. INTRODUCTION
Achieving healthy sustainable food systems requires large reductions in food loss and waste, together with improved food production practices [1]. Within this context, from 2012, several nations adopted fortification policies to include vegetable oil as a fortified delivery mechanism [2,3]. Recently, several food manufacturers, have studied fortification of palm based vegetable cooking oil with vitamin A [4,5].
Edible oil fortification, is a potentially useful means of expanding the present reach of vitamin A [6] But, stability is shown to be problematic in some environments [8,5]. Factors such as acidity, moisture, ultraviolet light, oxygen and heat are well established causes [9 -13]. Clearly, given new global challenges of delivering sustainable food systems, attention should also be considered, not only for the food system itself, but also for the total delivery mechanism, which may be derived from natural materials used to protect the food system [1]. Undeniably, there is still continued interest to establish the most ideal methods for determining the most suitable environmental conditions and packaging materials [14] for long-term vitamin stabilisation [15,16]. A recent study [5], noted several effects from choice of packaging material, to protect vitamin A and noted beneficial effects of Polyethylene Terepthalate (PET) vs transparent nylon, due to improved gas transmission and water vapour permeance. Opaque Nylon improved vitamin A retention, vs transparent PET, because vitamin A is more accute to UV light [17] than oxygen attack [18,19].
Although, others [5] previously considered the effects of differing packaging materials on vitamin A degradation, the longest experimental design that we are aware of was only for six months [6]. No literature exists to explain the effect of illuminance on fortified vegetable oil using commercial packaging materials beyond six months in typical environmental shelf-life conditions. Consequently, this study is a continuation and update of previous studies at several isothermal conditions using normal commercial food grade packaging. Refined Bleached Deodorised Palm Olein (RBDPOL) was used and preferred for its superior oxidative stability. Antioxidants were excluded [20,5,6]. Described previously [5,6], preparations of RBDPOL and vitamin A 1.0 mio IU (retinyl palmitate) were assembled in laboratory conditions at concentrations of 70 IU g-1 and 45 IU g-1, at two temperature ranges; first 18-22 o C, and 32-33°C, for a total duration of twelve months [21,22,25]. and illuminance were determined by the same methods described above and previous [6].

Quantification of vitamin A by high performance liquid chromatography (HPLC)
The vitamin A was determined by liquid chromatography method [26]. Standardized vitamin A (Retinyl palmitate) was supplied from Supelco-Sigma Aldrich (purity 93.8%). HPLC determination is described previously [6]

Statistical analysis
Statistical analysis was first examined using a combination of Student t-test to determine uncertainty [27]. Final analysis was carried out using analysis of variance (α = 0.05) with MiniTab v.16.1.1 software.

Calibration of Vitamin A
A calibration of vitamin A level concentration (IU/g) is shown previously in [5]. Calculations show corellation between peak area obtained from analysis using HPLC and regression of linearity. Figures 1 and 2 Table 4, shows that temperature storage is probably contributing the biggest impact to degradation of vitamin A. After twelve (12) months monitoring, all samples stored at 18-22 o C had vitamin A degradation of approximately 10-15%. Whereas, all samples stored at 32-33 o C degraded by approximately 16-22%. These data confirm similar findings [5].

Correlation of PV value to vitamin A degradation
As described previously [5], for vitamin A fortification studies, the peroxide value (PV) was monitored to acceptable level of 10 meq kg -1 [20]. Figures 3 and 4 show the effect of peroxide (PV) to decrease vitamin A. Linearity was observed for 45 ppm (y = -0.3106x + 43.035) and 70 ppm (y = -0.603x + 67.149). This confirms a similar tendency noted by others for a compound decrease of vitamin A in oxidized oil [5,28,29].   16-22%. These data confirm similar findings [5].

Correlation of PV value to vitamin A degradation
As described previously [5], for vitamin A fortification studies, the peroxide value (PV) was monitored to acceptable level of 10 meq kg -1 [20]. Figures 3 and 4 show the effect of peroxide (PV) to decrease vitamin A. Linearity was observed for 45 ppm (y = -0.3106x + 43.035) and 70 ppm (y = -0.603x + 67.149). This confirms a similar tendency noted by others for a compound decrease of vitamin A in oxidized oil [5,28,29]. This more extensive study validates previous research [5,6] on the impact of environmental effects of fortified vegetable frying oil, during extensive storage life periods. These results show that cooler storage conditions, low illuminance or low UV light adsorbent packaging could aid to minimize excessive vitamin A depletion during distribution and storage [13,15,30]. Our results further suggest the benefits in selecting suitable contact packaging materials, which are able to minimize illuminance from natural or artificial UV light [16,5], together with optimal storage temperatures to maximize vitamin A retention. Outcomes from this study may be of importance for food product developers, when fortified vegetable products are frequently sent via food aid programs to localities having insufficient storage controls [30].

IV. CONCLUSION
After 12 months monitoring, the degradation of vitamin A was above 15% at the lowest temperature and ~38%± at the highest temperature. This confirms previous findings [5], that fortification 45 IU g-1 in vegetable frying oil is likely insufficient to maintain the Vitamin A level above 20 IU g-1 over entire storage life.
The effect of prolonged storage at elevated temperatures has a vivid effect. Cooler condition (18-22 o C), retained significantly more vitamin A vs samples stored at higher (31-33 o C) temperatures [5]. This study further reinforces the advantage of storing fortified oil in suitable low illuminance, away from direct light. Hence, controlled storage will help retain maximum vitamin A concentration [15].
This study excluded antioxidants to avoid distortion of results. Hence, a next step from these findings is to understand the effect of antioxidant addition; and additionally, the effect of new recycled or biodegradable food contact materials on fortified vegetable oil based systems.