The Potential Contribution of Water-Soluble Vitamins in Ready Meals to the UK Reference Nutrient Intakes

Abstract

The UK ready meal (RM) food industry had an estimated value of £2.7 billion in 2017/18. These meals are a convenient option for many people and are described as a processed food that require reheating before consumption. However, food processing techniques such as heating, irradiation, and freezing can degrade process labile nutrients, especially essential water-soluble vitamins (WSVs), B-vitamins and vitamin C.

Although RMs are an increasingly popular meal option, little is known about the contribution of these meals to the dietary intake of those that are consuming RMs. There is no current guidance available for the recommended nutrient content of RMs, however, Public Health England recommend that meals served as part of public catering should provide at least 30% of the reference nutrient intake (RNI) for all micronutrients for adults when the serving is considered a ‘main meal’.

Due to the functional importance of these vitamins, it is imperative to have accurate estimations of nutrients present in the reheated RM. The most susceptible to degradation during food processing are B-group vitamins; thiamine (vitamin B1), riboflavin (vitamin B2) and folate (vitamin B9), and vitamin C. The rise in consumption of RMs mean that it is important to understand the potential contribution of these meals to the UK diet. Therefore, the aim of this research is to assess the thiamine, riboflavin, folate, vitamin B12 and vitamin C content of a popular RM in the UK. This study will highlight opportunities to enhance the WSV quality of meals where these nutrients may be lacking.

A literature review taking a systematic approach was carried out to determine the current patterns of RM consumption in the UK, along with the thiamine, riboflavin, folate, vitamin B12 and vitamin C content of RMs. Five academic articles met the inclusion criteria for consumption, and 15 that examined the nutrient content of RMs, respectively. The review concluded that RMs were consumed 1-2 times per week by the majority of RM consumers, and that those with annual household incomes below £20,000 were the population group most likely to consume RMs.

Analysis of RMs found that vitamin C had the greatest susceptibility to processing including, heating, freezing and storage. Thiamine, riboflavin, folate was liable to processing through hot-holding, irradiation and storage. Vitamin B12 was the least labile of the vitamins reviewed, however only one study analysed the vitamin B12 content of RMs.

Secondary analysis of the National Diet and Nutrition Survey (NDNS) revealed that RMs did not meet the 30% RNI for WSV recommendation for folate and vitamin C. The 30% of the RNI recommendations were met for thiamine, riboflavin and vitamin B12. There was no difference in income between those that consumed RMs and those that did not.

Chemical testing was used to quantify the thiamine, riboflavin, folate and vitamin C content of the RMs. Thiamine method testing revealed that High-Performance Liquid Chromatography (HPLC) was the most accurate method. Vitamin B12 was not analysed because of safety issues associated with quantifying the vitamin.

The thiamine, riboflavin (analysed by HPLC with fluorescence detection), folate (analysed using the Vitafast microbiological assay) and vitamin C (analysed by Campden BRI) content of the sausage and mashed potato RMs were significantly different between five different RMs from four providers. None of the RMs tested met the 30% of the RNI for WSV recommendations for riboflavin, folate, and vitamin C, although they did for thiamine. Lastly, the effect of hot-holding, a method used by catering services to keep food warm, on WSVs was determined. The study found that hot-holding RMs for three-hours at 90oC led to a significant increase in folate concentration in the vegetable portion (peas), but there was no effect on other meal components or vitamins.

This research has shown that there is a need for more accurate information regarding nutrient content of RMs, especially food targeted at older adults, a population group who are at greater risk of nutrient deficiency. Reformulation of RMs, such as incorporating more vegetables into RMs would increase the WSV content of these meals.