Reestimating the role of leaching for loss of water-soluble vitamins in processed vegetables
Centre Inra Provence-Alpes-Côte d’Azur Domaine Saint-Paul
Site Agroparc CS 40509
84914 Avignon Cedex 9 28
thEFFoST Conference, 25-28 nov 2014, Uppsala, Sweden.
Raw material
Blanching
Addition of covering juice Cleaning
Trimmming
Sterilisation Final product
Canning of green beans – losses of folate through diffusion to the covering liquid
Transfer
IMMERSION 30 - 1 min 15 - 30°C
ASPERSION / IMMERSION 4 - 8 min 85 - 95°C
6 - 15 min 125 - 130°C
Catabolism during storage Diffusion
Degradation / diffusion
Degradation Diffusion
Main steps Sampling points Total folates Potential mechanisms
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
a
a
a
a
b
mg/kg FW as 5-CH3H4folate-Glu1
Health benefits of fruit and vegetables are mainly linked to their contribution to the diet for fibers, minerals (K, Ca) and vitamins, especially vitamin C (ascorbic acid), vitamin B9 (folate) and provitamin A (carotenoids). Vegetables in particular, are almost systematically consumed after processing, whether industrial (freezing, canning…) or domestic (boiling, steaming,
microwaving…). Two mechanisms explain water-soluble vitamins losses from vegetables during heat-treated in presence of water,
namely degradation and leaching. Structure of the folate vitamers Ascorbic acid
Folates were analyzed along an industrial canning chain (5 repetitions), at 5 sampling points.
During industrial processing, total folate content decreased significantly, by 30% in green beans after sterilization, with 20%
of the initial amount being transferred into the covering liquid just after canning.
Raw material Final
product Covering
liquid 0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Folate content (mg/kg as folicacid)
This loss by transfer was confirmed by analysis of raw materials, canned green beans and covering liquid 1 month after processing, over a production season: concentrations were equilibrated between vegetable and covering liquid, with limited chemical degradation.
Leaching is highly relevant to water-soluble vitamins losses when heat treatments occur in presence of water or a covering liquid. Leaching takes place particularly at the start of any heating step. This is modulated by vegetable’s shape and size and temperature. Quantifying losses in water-soluble vitamins therefore requires more emphasis on the determination of diffusion parameters.
Delchier N., Reich M. & Renard C.M.G.C.: Impact of cooking methods on folates, ascorbic acid and lutein in green beans (Phaseolus vulgaris) and spinach (Spinacea oleracea). LWT-Food Science and Technology49(2012) 197-201.
Delchier, N., Ringling C., Le Grandois J., Aoude-Werner D., Galland R., Georgé S., Rychlik M. & Renard C.M.G.C.: Effects of industrial processing on folate content in green vegetables. Food Chemistry139 (2013) 815-824
Delchier N., Ringling, C., Maingonnat, J.-F., Rychlik, M. & Renard C.M.G.C. Mechanisms of folate loss during processing: diffusion vs heat degradation.
Food Chemistry, in press
This work was funded by ANR ALID RIBENUT project
Chemical degradation and leaching for green peas and brussel sprouts
Domestic cooking of frozen vegetables
O
O OH H
O O
H O H
Losses in vitamin C were followed in fresh peas and Brussel sprouts, submitted to the same thermal treatment either sous-vide (hermetically sealed pouches) or immersed in water in open nets. This allowed to compare the losses due to thermal degradation and to leaching.
Much higher losses were observed when the vegetables were in contact with water, specially for peas, the smaller vegetable
Fick’s second law and first order degradation kinetics models were used to quantify the relative impact of the two mechanisms.
Impact of common domestic cooking practices was assessed for frozen vegetables. Higher losses were observed for cooking in boiling water for both vitamin C and folates and for all vegetables.
PC: pressure cooker; BW: boiling water; ST: steaming; MW: microwave
Catherine M.G.C. Renard, Nicolas Delchier, Hannah Brick, Caroline Garcia, Sylvie Bureau, Line Touloumet, Stéphane Georgé*
& Jean-François Maingonnat
UMR408 "Sécurité et qualité des Produits d'Origine Végétale", INRA, Université d'Avignon, F-84000 Avignon, France
*CTCPA, site Agroparc, F-84000 Avignon, France
T0 PC BW ST MW
0 0.1 0.2 0.3 0.4
Green beans
0 0.1 0.2 0.3
0.4 Cauliflower
0.4 T0 PC BW ST MW T0 PC BW ST MW
0 0.1 0.2
0.3 Spinach
0.4
Folates (mg/kg dw)
0 200 400 600 800 1000
1200 Brussel sprouts
0 100 200 300 400
Fresh peas
0 20 40 60 80 100
Spinach
T0 PC BW ST MW
T0 PC BW ST MW T0 PC BW ST MW
Vitamin C (mg/kg dw)
Green beans Cauliflower Spinach
Brussel sprouts Fresh peas Spinach
Peas – Thermal treatment
0 0.2 0.4 0.6 0.8 1 1.2
0 60 120 180 240 300
0 0.2 0.4 0.6 0.8 1 1.2
0 60 120 180 240 300
0 0.2 0.4 0.6 0.8 1 1.2
0 60 120 180 240 300
Time (min) Time (min)
Time (min)
Peas – Thermal treatment plus leaching
Brussel sprouts – Thermal treatment plus leaching C/C0
C/C0 C/C0
25°C 45°C 65°C 85°C
0 0.2 0.4 0.6 0.8 1 1.2
0 60 120 180 240 300
Time (min)
0 0.2 0.4 0.6 0.8 1 1.2
0 60 120 180 240 300
Time (min)
‐
_ _ _ _ _
25°C 85°C
--- Measured loss by degradation; Measured loss by degradation plus leaching; Estimated impact of leaching
Concentration ratio to initial C/C0
