The use of Aqua Salvo™ on value added vegetable products

The findings in this report are based on trail procedures and experimentation conducted inside a vegetable processing factory.  The true scientific nature thereof and the final conclusions are not reproducible in laboratory conditions.

Report compiled by Fanie Verwey

BSc. (Agric) Plant pathology/Plant protection
Production &food safety manager
Harvestfresh Farms cc.                       April, 2007

Introduction

Aqua Salveo™ was used as a follow-on disinfecting treatment in the Harvestfresh vegetable processing factory.
Trails were conducted using lettuce, spinach, cauliflower, broccoli and several combinations of commercial vegetable mixtures (i.e. mixed lettuce, stirfry, caulibroc etc.).  All production procedures, i.e. trimming, cutting, washing, packing and storing conditions of vegetables were kept the same as per normal.

Aqua Salveo™ was only included as a final rinsing agent at 0.01% concentration (0.1ml/L of water) before drying and packing of the processed vegetables products.  It was found that the use of Aqua Salveo™, in combination with standardized chlorine treatment, improved the shelf-life of processed vegetable products.

Materials and methods

(1) In vitro procedure:

Normally prepared broccoli, cauliflower and carrot cuttings were weighed of in 1.5kg (1,500g) portions and separately treated (dipped) in 10L of chlorinated water (at 200ppm active chlorine).  After the chlorine treatment for 10 minutes, 750g portions (half of the original samples) were taken out and separately treated in 10L of a 0.01% Aqua Salveo™ solution (i.e. 1ml/10L of water), also for 10min.  The remaining half (750g) of the produce were only rinsed using clean potable water (as per normal production procedures).

From the above 750g treatments for each broccoli, cauliflower and carrots (a) in chlorine on the one hand and (b) in chlorine + Aqua Salveo™ on the other hand; 3x 250g samples were separately packed in plastic bags.  The final resulting triplicate treatments (3x broccoli in chlorine, 3x broccoli in chlorine + Aqua Salveo™,
3x cauliflower in chlorine, 3x cauliflower in chlorine + Aqua Salveo™, 3x carrots in chlorine, and 3x carrots
in chlorine + Aqua Salveo™) were stored in refrigerated conditions at +5.0ºC.

Daily assessments were done in order to evaluate the efficacy of the different treatments on separately packed broccoli, cauliflower and carrot samples.  Without opening the plastic bags in which the products were packed, physical appearance and shelf-life were the main criteria, in which case browning, wilting or any other visible signs of deterioration were noted.  Finally, samples were sent off for microbial analysis on the normal date of expiry (sell-by-date).  This was in accordance with the standard 1+4 day shelf-life for these prepared and packed vegetable products, meaning the same date of production plus 4 days thereafter.  Standard microbial tests were conducted including a total plate count, total Enterobacteria count, detection of E. coli and Salmonella spp.

(2) In sito procedure:

The use of Aqua Salveo™ was included as a standard procedure by adding 100ml of the product to 1,000L of water in a second rinsing bath (after the initial washing treatment – see diagram below).  Produce in the process of washing and rinsing is driven forward by means of a moving stream of recirculating water.

For the experiment, normally prepared produce (a) mixed lettuce and (b) cut spinach, were washed and rinsed in the 1st and in the 2nd baths.  The 1st washing bath is equipped with an automated chlorination unit that uses calcium hypochlorite, and maintains a 200ppm concentration of active chlorine in the water.  100ml of Aqua Salveo™ were mixed into the 2nd rinsing bath 10min. before the onset of the operation (thus also resulting a 0.01% dilution as in the previous experiment described above).

Exposure time in each of the 2 baths varied between 3 and 5min.  For control purposes, washed produce from the 1st bath were intercepted before it ran over into the 2nd rinsing bath (containing the Aqua Salveo™ solution).  The intercepted produce was rinsed off in clean potable water not containing any chemical additives, thus serving as an ‘untreated’ control.  After rinsing procedures, the lettuce mixture and the spinach from the 2 different treatments were dried off and packed in form-film plastic as per normal procedures.

 


3 ‘pillow packed’ samples from both mixed lettuce and spinach were randomly selected from each of the clean water and Aqua Salveo™ rinsing treatments.  These samples were stored in refrigerated conditions at +5ºC for further assessment.  Assessment procedures on the final packed products were followed in exactly the same way as for the in vitro experiments (above).

Results

Based on visual observation over time periods correlated with sell-by-date standards, the effect of natural deterioration (due to microbial activity) was not as dramatic in cases where Aqua Salveo™ was used during rinsing procedures.  Even compared to the normal chlorine treatments, the addition of Aqua Salveo™ significantly improved the visual characteristics of fresh produce up to a few days after packing procedures.

Microbial tests were conducted with randomly selected samples of the products at a certified, independent laboratory.  The results revealed a significant decline in the number of bacterial and fungal colony forming units (cfu’s) per gram of product analysed (figures available on request).  None of the results from using clean rinsing water, or rinsing water containing Aqua Salveo™, showed out the presence of either E. coli or Salmonella spp.

Conclusions

Processed vegetable products inside plastic packaging tend to discolour and wilt as a result of microbial activity on and moisture loss from the exposed surfaces.  This effect is enhanced in cases where additional exposed surfaces are caused by cutting procedures associated with the preparation of value added vegetable products.  Treatment of fresh produce with chlorine related products are well known to have an inhibiting effect on this process.

In most cases where chlorine and/or related products are used, a final rinsing procedure is used to relieve the residual effect that these products have on prepared fresh produce.  The use of Aqua Salveo™ is well positioned as an amendment to this final rinsing process.  Experimentation in this regard yielded positive results on value added broccoli, cauliflower, carrots, lettuce, and spinach products.  To summarize it can be concluded that in cases where calcium hypochlorite and Aqua Salveo™ were used for washing and rinsing procedures, shelf-life (based on the intensity of microbial activity) was significantly improved.

Metals, such as zink, copper and silver, are known to act as anti-microbial agents.  The nitrate salts of these agents in Aqua Salveo™ can thus be assumed to contribute towards the enhanced shelf-life noted on the treated vegetable products.  Upon subjecting the treated samples to laboratory tests, it was clear that the plate counts were significantly lower on produce that was rinsed in Aqua Salveo™.

It is important to consider the shelf-life of fresh cut vegetables as a criterion when evaluating the efficacy of chemical agents applied as a post-harvest treatment.  This allows various advantages for producers (packers), distributors and the end-users (1) packed products does last longer allowing better planning from a production and distribution point of view, (2) end-users will also benefit from the fact that prepared vegetable products will remain fresh for longer periods of time.

Aqua Salveo™ also holds a SABS mark and comprehensive documentation, such as the Material Safety Data Sheets (MSDS).  These accreditations substantiate the fact that the product is a non-toxic compound, perfectly fit for use in food processing factories and that these attributes also minimize the risk of chemical contamination.